SMA Urban Tree of the Year 2020

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A huge specimen of common hackberry (Celtis occidentalis). Photo: chadwickarboretum.osu.edu

Every year, members of the Society of Municipal Arborists (SMA) nominate and vote for the SMA Urban Tree of the Year. This tradition dates to 1996 when ‘Princeton Sentry’ ginkgo (Ginkgo biloba ‘Princeton Sentry’) was crowned. 

For 2020, the Urban Tree of the Year is the common hackberry (Celtis occidentalis). 

Common Hackberry

Hackberry tree natural distribution map.
Distribution of common hackberry (Celtis occidentalis). Ill.: nysufc.org

This tree occurs in the wild from the US Mid-Atlantic in the east to Wyoming in the west up into Quebec, Ontario and Manitoba in the north. In its natural range, it’s sometimes found in rocky, alkaline sites many other trees shun, although mostly in well-drained, fairly moist soils. It doesn’t seem to mind either the hot, humid summers of Alabama and Georgia, nor the cold, snowy winters of Montreal or Toronto. Its hardiness range is quite astounding: USDA hardiness zones 2 to 9 (AgCan zones 3 to 9). And it’s long-lived: many specimens attain the ripe old age of 150 years; some many more.

The hackberries were originally placed in the elm family (Ulmaceae), but taxonomists recently moved them into the hemp family (Cannabinaceae).

More a Workhorse Than a Stunner

Hackberry tree
A hackberry is attractive enough, but it won’t bowl you over. Photo: Chhe, Wikimedia Commons

Let me be brutally honest: the common hackberry is not a particularly showy tree. You don’t go “wow!” when you see one. The flowers are nondescript, the leaves are—well—ordinary and the berries, too small to be striking. In its normal forest setting, it just sort of blends in. Big specimens, with massive trunks and intriguing bark, are charming, but you have to wait a while for those.

Think of the common hackberry instead as a workhorse tree: it grows robustly, adapts to just any about condition, even the toughest ones (although not severe drought) and will be moderately attractive all year long, but it just won’t knock your socks off. Of course, for North Americans, its native status is a plus. A species you can add to your repertoire of useful native trees.

The common hackberry is a medium to large-sized deciduous tree, generally reaching 40 to 60 feet (12 to 18 m) in height and about the same in spread, with exceptional specimens approaching 100 feet (30 m) tall. It’s fairly fast-growing and can be rounded to vase-shaped in silhouette.

Ridged bark on mature tree.
The corky ridged bark of mature trees is unique. Photo by Michelle Sutton

It’s sometimes confused with the American elm (Ulmus americana) because of its similar growth habit and leaves, and indeed, it is often used as a substitute for that species where Dutch elm disease is a problem, but it’s readily told from its doppelganger by its very distinctive bark, smooth and grayish when young, light brown to pale gray at maturity, usually with distinct corky ridges as it ages. And of course, its small round fruits look nothing like elm’s winged seeds. 

Hackberry berries
The berries are edible, but the pit it big and there isn’t much flesh on them. Photo: sciencing.com

The berries (officially drupes) are green in summer, then turn orange-red to dark purple in the fall, often staying on the trees for several months. They are edible, rich in protein and somewhat sweet, attracting birds like robins. mockingbirds and cedar waxwings. Since they persist through the fall and into winter, they offer a vital source of food for migrating birds. And the birds carry the seeds from place to place, which explains the tree’s vast distribution.

hackberry leaves showing differences in form
People often mistake hackberry leaves for elm leaves. Photo: Sairus Patel, trees.stanford.edu

The lightly toothed leaves are alternate and variable in shape, from ovate to egg-shaped to nearly lanceolate, mid-green and rough on the top, whitish underneath. They turn light yellow in the fall. The inconspicuous flowers are wind pollinated.

As an Urban Tree

Common hackberry on a city street.
Common hackberry makes a wonderful urban tree, adapting well to tight spaces and poor growing conditions. Photo: plants.bachmanslandscaping.com

As a subject for urban tree planting, the hackberry has the ability to tolerate air pollution, road salt and urban conditions, including a wide range of soils, even temporarily flooded ones. It’s an excellent choice as a street tree, for parks and green spaces and can be planted along rivers to help prevent erosion and minimize the risk from flooding.

Insect Pests

American snout butterfly with orange and brown wings dotted with white.
The curious and attractive American snout butterfly (Libytheana carinenta) feeds exclusively on hackberry leaves. Photo: butterfliesathome.com

There are butterflies—and attractive ones at that!—whose caterpillars feed on hackberry leaves. Some (the American snout butterfly, the tawny emperor and the hackberry emperor) are even specific to hackberries and feed on no other plant. Since damage due to caterpillars is rarely important and you get to enjoy beautiful butterflies, this may be seen as more a plus than a minus!

 hackberry nipple gall on a leaf
The hackberry nipple gall, due to a tiny psyllid, Pachypsylla celtidivescula, is surprising, but harmless to the tree. Just ignore it. Photo: handyandysnursery.com

Hackberries do sometimes suffer from greenish leaf galls, but if you follow the 15-pace rule (if you can’t see the problem at 15 paces, it’s not worth treating), they’re not much to worry about and rarely weaken the tree. 

Witches’-broom on celtis
Witches’-brooms are mostly noticed during the winter, when the tree is leafless. Photo: jocelynsgarden.blogspot.com

A witches’-broom (abnormal stem growth) due to mites living in symbiosis with a fungus, can occur in some areas and can be quite visible, especially in winter. It would be best to avoid planting hackberries where that problem is common. One cultivar, ‘Prairie Pride’, is specifically recommended as being resistant to witches-broom and would make an interesting solution.

Prairie Sentinel™ (’JFS-KSU1’) with narrow columnar growth habit.
Prairie Sentinel™ (’JFS-KSU1’) hackberry. Photo: pepinieresavio.com

Speaking of cultivars, they aren’t widely available and, in most cases, seed-grown trees are perfectly acceptable for urban use. Among the few that are available, the aforementioned ‘Prairie Pride’ has a more compact, oval crown and thicker, leathery leaves while Prairie Sentinel™ (’JFS-KSU1’) is a tight columnar form no more than 12 feet (3.5 m) diameter.

For more information on the Urban Tree of the Year program, don’t hesitate to contact the Society of Municipal Arborists

A Kitchen Tool for Your Cactus

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Ill.: clipartmax.com & pikpng.com

Spiny houseplants like cactus and euphorbias are awkward to handle. You reach you hand down to move them and … ouch *&?%#! 

However, you can borrow a tool from your kitchen to move them readily: simple kitchen tongs! 

Just open the tongs and grasp the pot. Then you can move it, turn it or do pretty much anything you want with it while keeping a safe distance. 

You can even hold the plant body itself with the tongs. Photo: happydiyhome.com

You can even use the tongs to hold the plant itself when repotting or to grab cuttings to twist them free.

You might even want to hang the tongs from a hook near your prickly plants for easy access next time around.

Sometimes the simplest techniques are the most effective!

Clover in the Lawn: From Friend to Weed to Friend Again!

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How did such a wonderful plant as clover come to be considered a weed? Photo: life.shared.com

Here’s a quick overview of the incredible story of a simple little plant, white clover (Trifolium repens), and how it went from being the best friend a lawn ever had to being considered a noxious and despised weed to once again getting into the home gardener’s good graces. How is that even possible? Read on and you’ll understand!

500 Years of Popularity

16th century sketch of lawn bowling.
White clover was always part of a lawn, even in its early days here in the 16h Century England. Photo: northlondonbowlingclub.co.uk

Since the advent of lawns during the Renaissance, white clover has always been, along with turf grasses, the one of its main components. Until the 1950s, it was considered normal for any lawn to have a good share of clover and when the first commercial grass seed was offered back in 1780, it was actually a mix of grass and clover seed.

Gardeners had long observed that lawns containing clover were greener and healthier than those where clover was lacking. During the first centuries of lawn use, of course, no one knew why grasses always grew better in the company of clover plants, although the difference was well known. A lawn with a decent share of clover was greener, suffered less from drought and insect damage, and had fewer undesirable plants such as thistles.

Today we understand a little more why turf grasses do better when accompanied by clover.

Nodules on clover roots.
Nitrogen-fixing nodules on the roots of white clover. In the photo to the right, one nodule is cut in half, showing the pinkish-red coloration that indicates nitrogen fixation. Photo: sciencelearn.org.nz

Among other things, we know a lot more about fertilization today and clover is almost a classic example of a plant that enriches the soil. Clover is a legume—a member of the Fabaceae family—and lives in symbiosis with bacteria that fix atmospheric nitrogen and make it available not only to the clover itself, but also to neighboring plants. That makes turf grow greener, even in the absence of fertilizer. And the extra nitrogen also helps explain the lessened weed infestations noted in clover-rich lawns. The abundance of nitrogen results in denser turf and that leaves less room for unwanted weeds.

Another detail: thanks to its deep roots, clover is more tolerant of drought than most grasses and remains green even when drought is severe. As functional lawn irrigation systems didn’t exist until the 20th century and therefore lawns were rarely watered, this was an important factor. Plus clover is very resistant to other weather-based problems, resisting damage from snow, ice, rain and even flooding. As a result, it will grow in most climates other than the very driest ones and in hardiness zones 3 through 10.

Another advantage of clover is that it’s a naturally low-growing plant needing less mowing than lawn grasses, so its presence doesn’t increase the frequency of mowing.

In addition, most serious lawn pests have a “thing” for grasses, not clover. Pests like white grubs, chinch bugs, leatherjackets and sod webworms find clover of little interest and rarely settle in great numbers in a clover-rich lawn. They prefer turf grass monocultures.

Lawn with clover flowers.
The beautiful flowers of the clover add to their appeal. Photo: 4.bp.blogspot.com

And the gardeners of ages past appreciated the presence of the magnificent little white clover flowers that decorated the vast green carpet that could otherwise be a bit monotonous.

So, for the first 500 years of the lawn’s history, no one would have thought of trying to remove clover from the lawn: it was a considered essential for healthy turf.

Turning a Friend into an Enemy

Bottle of 2,4-D
2,4-D herbicide was the first “lawn herbicide,” one capable of killing broadleaf plants, but without harming turf grasses. Photo: Mustbest.com

Then came the 1950s. A multinational chemical company, Dow Chemical, had successfully developed a new product, 2,4-D. It was a “selective herbicide”, meaning it could control lawn weeds without harming grasses. There was just one problem. It left grasses, with their thin leaves, relatively intact, but killed broadleaf plants indiscriminately. There was the potential to make billions of dollars in profit if this product (and other similar herbicides) could be successfully sold to lawn owners. But 2,4-D also killed the clover people loved. What to do?

The secret was to turn clover from a friend into an enemy. Pesticide companies decided to launch an intensive advertising campaign to convince homeowners that white clover was a weed that needed to be destroyed. They spent literally millions on advertising to persuade unconvinced gardeners.

Book on lawn herbicides
This book reveals the program designed to demonize clover in lawns. Photo: amazon.com

It wasn’t easy at first to convince experienced gardeners to give up clover. This what Dr. R. Milton Carleton, one of the discovers of 2,4-D, wrote about it:

“The thought of White Dutch Clover as a lawn weed will come as a distinct shock to old-time gardeners. I can remember the day when lawn mixtures were judged for quality by the percentage of clover seed they contained. The higher this figure, the better the mixture… I can remember the loving care which old-time gardeners gave their clover lawns. The smug look on the face of the proud homeowner whose stand was the best in the neighborhood was really something to behold.” (From New Way to Kill Weeds In Your Lawn And Garden by R. Milton Carleton, 1957. Arco Publishing Co., N.Y.)

Imagine this from the mouth of the father of 2,4-D! He concluded, however, that the situation had changed and that the time had come to abandon the use of clover as part of a quality lawn. He strongly believed that herbicides were the way of the future.

After 50 Years of Negative Press

White clover flower
The time has come to bring clover back to our lawns. Photo: plantsoftheworldonline.org

But times have changed … yet again. After more than 50 years of use, Dr. Carleton’s miraculous herbicides have been shown to be silent killers, disrupting soil microbes, birds and animals, poisoning adults, children and pets, damaging shrubs, trees and vegetable beds, and have caused enormous harm to our environment, so much so that they are now banned in several countries. So, it would appear that the time has come to put aside herbicides toxic to the environment and look back at clover as a useful, and perhaps essential, part of any beautiful lawn.

That said, it’s hard to erase 50 years of condemnation. Today’s multinational lawn treatment companies continue to promote lawn herbicides as friendly and harmless, despite abundant proof to the contrary. They have been so successful in their propaganda that most gardeners today still believe that clover is a weed when it grows in a lawn. Look it up on the Internet and you’ll see. About half the articles about clover in lawn are still about how to remove it, not how to encourage it. It’s going to be difficult to convince a lot of lawn owners otherwise.

Still, the idea of reintroducing clover to lawns is catching on and more and more homeowners are once again proud of their clover-enriched lawns. And herbicide-using lawn owners are starting become a bit frustrated with the poor results they’re getting. Insect problems, diseases, weeds, lawn dieback: it adds up to a lot of moolah for very ordinary results. 

Where I live in eastern Canada, last summer was disastrous for turf lawns. A combination of drought, extreme heat and insect infestations literally wiped out lawns everywhere. Yet, some lawns remained green and healthy with little to no care: mostly those with a lot of white clover. It was enough to make some neighbors jealous. Now, if only they could make the link between tougher, greener lawns and the presence of clover in those lawns, the battle would be largely won.

Micro-clover lawn compared to grass lawn.
Lawn with micro-clover in the foreground. Notice how much greener it is than the neighboring grass turf. Photo: whygoodnature.com

Even lawns that are entirely composed of clover are increasingly seen, especially micro-clover lawns. Micro-clover (Trifolium repens ‘Pipolina’) is a selection of white clover with smaller and denser leaves that requires even less mowing than a regular white clover lawn. The clover lawn phenomenon is popping up all over in our cities and suburbs. Probably one of your neighbors has one if you don’t already.

Don’t Let Lawn Care Companies Ruin Your Clover Lawn

If you hire a lawn care company and you’re a person who considers the presence of clover in a lawn important, it’s vital to tell them that. They still routinely use herbicides that kill clover and won’t hesitate to apply them unless you insist. They’ve even found inventive ways around laws passed to ban the use of “cosmetic pesticides” on lawns. It would be sad to see your little clover colony poisoned.

Long live clover in lawns. And long may it reign!

Terracotta or Plastic Pots for Succulents?

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Ill.: leafandclay.co, montage laidbackgardener.blog

Question: Is it better to use plastic or terracotta pots for succulents and cactus?

C.T.

Answer: This an old debate, going back to at least the late 1960s when I first became interested in houseplants. At the time, I was told succulents and cactus, which are a type of succulent, did best in terracotta pots (unglazed pottery) because the pots “breathed” (were porous) and allowed more air to reach the roots. And because they’re porous, they lost water more rapidly and succulents didn’t like sitting in wet soil. It made sense then and there is indeed a certain truth to it, but…

In fact, you can grow succulents just as easily in plastic pots as terracotta ones. And with terracotta pots being so expensive these days, I suspect most succulent-lovers use plastic more often than terracotta.

That “terracotta pots dry out faster than plastic ones” really makes little difference as long as you use a potting mix with lots of air spaces (potting mixes have become dramatically better aerated since the 1960s!) and water your plants correctly, that is, waiting until the growing mix is thoroughly dry before watering again. The soil in terracotta pots may dry out a little faster, but if the plant is correctly planted in well-aerated soil, the difference will likely be minor. 

Watering can watering succulents in pots.
As long as you water your succulents appropriately, it really doesn’t matter whether you grow them in terracotta pots or plastic ones. Photo: urbanorganicyield.com

Still, if you tend to overwater (and ideally, you’d learn not to do so!), terracotta pots might be a better choice. That would also be true if you tend to stick your succulents in dark corners where they receive insufficient light and therefore grow little and use little water, but… you shouldn’t be mistreating your succulents like that anyway. (They all like plenty of light!) 

The corollary of the above is that if you’re someone who tends to forget to water, you should probably go for plastic. That might just keep a severely drought-stressed succulent alive a day or two longer.

Of course, if you’re just a regular houseplant owner who pays attention to watering needs, you can use either one.

What Commercial Succulent Growers Do

Nursery displaying succulents in plastic pots
If you visit a succulent or cactus nursery, you’ll probably discover they use plastic pots. Most do. Photo: Cactus & Succulent Nursery Tour 2019

I think it’s telling that commercial succulent nurseries, that once used terracotta pots almost exclusively, have pretty much all switched to plastic. Now, that’s largely for economic reasons—terracotta pots are just so expensive!—but if terracotta pots were really essential for keeping succulents healthy, they’d still be using them. 

In fact, the in-thing these days in succulent nurseries is to grow succulents in very thin, cheap plastic pots in the nursery, then to slip them into more ornamental cachepots to stimulate sales. When you water these, you just have to remove the “grow pot” from the cachepot 10 to 30 minutes after watering and drain away any surplus water from the cachepot. 

Other Pros and Cons of Terracotta and Plastic

  • Terracotta pots are heavier and can help hold up taller succulents better… but then, you could just as easily slip a plastic pot into a heavy cachepot.
  • As mentioned, terracotta is expensive. Some plastic pots are too, but you can readily find inexpensive ones.
  • Plastic pots can be seen as pollutants, unless you reuse them (which I do and assume most gardeners do) or recycle them (ditto).
White stains on terracotta pots
Terra cotta pots become covered with whitish stains … but that might be a good thing! Photo: mein-schoener-garten.de
  • Terracotta pots tend to develop whitish mineral stains on their outer surface over time, where water seeped through and evaporated. However, that liability can be seen an advantage: some designers think it is chic and are even calling it patina!
  • Plastic pots come in almost limitless sizes, shapes, textures and colors. There are even some that perfectly imitate terracotta! Terracotta is much more restricted. There is a good range of shapes and sizes and it could theoretically be offered in a wide range of colors (due to different clays as well as to dyes and stains), but usually it still comes in that well-known brownish-orange color we know as terracotta.
  • Terracotta is fragile and easily broken; most plastics, less so. But I don’t recommend dropping any kind of pot from a great height to test this. 
  • Plastics better tolerate freezing temperatures and some are, indeed, considered weatherproof. Never leave terracotta pots outdoors in freezing weather or they’ll crack. Still, just about any pot will last longer if you don’t leave it outside in freezing weather.
Terracotta pot shards in the bottom of a pot.
Pot shards at the bottom of pots are just a waste of space. Photo: lovelygreens.com
  • In the old days, terracotta pot shards—obtainable by (accidentally, one would hope) breaking terracotta pots—were widely used as a drainage layer in pots. But drainage layers have been considered a horticultural no-no for a generation now and, as a result, most terracotta shards probably now end up in the trash. 
  • Terracotta pots insulate plant roots better from heat than most plastic ones because they evaporate moisture (and evaporation has a cooling effect) and are also fairly thick. Black and other dark shades of plastic can really heat up the soil in a pot if they’re placed in full sun. But if heat is a problem, you could get a similar result by using white and other pale shades of plastic or slipping the pot inside a pale-colored cache-pot. 

In most cases, though, it really doesn’t matter what kind of pot you plant your succulents in… as long as it has a drainage hole!

What is Urban Ecology and Why is it Important?

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An article by Ryan Taylor of Colorado State University and representing the Sustainable Secure Food Blog

In the summer of 2007, humanity reached a milestone. For the first time in human history, more people were living in cities than in rural areas. Those people need food, clean water and air, and other necessities of modern living.

At the turn of the 20th century, with more people living in cities, residents lived further from food production sources. This put a burden on the agricultural land for food production, and meant an increase in transportation costs. Additionally, handling fresh food became a new industry within our urban culture.

City street in New York crowded with people.
In 2007, humanity reached a turning point. More people live in cities than in rural areas. Photo: Morguefile

Urban ecology provides answers to these and many other questions so that our cities can thrive—without harming the people, plants, and animals living there. This new area of science can also benefit those areas. It can help cities learn to re-use natural resources through recycling of nutrients that are hyper-consolidated in the urban environment.

One of the interesting questions urban ecology wrestles with is urban food production and the impact it has on cities and human health. A well-known ecological principle that pertains to diversity is that the more species diversity you have in a system, the healthier that system is. It’s also more resilient. For example, the Irish Potato Blight occurred mostly because farmers were only growing one type of potato. This made those potatoes—and the entire crop—more susceptible to any insect or microbial attacks. (For more on that, read this blog.) As a result millions of people were displaced from their homes and their heritage.

Invasive species also create similar problems to those the potato farmers encountered. The emerald ash borer which is native to Asia is one such story. The small green beetle has come to North America. This beetle has few natural predators on its new continent. Thus it has started to destroy our native ash trees (Fraxinus spp.). Currently 15% of Colorado’s urban forests are ash, and there are 1.45 million ash trees alone just within the city of Denver. That meant that when the emerald ash borer migrated to the area, there was no natural defense against this invasive insect. Without treatment, the trees were killed. It’s definitely a tragedy—but one that we can definitely learn from. Whether it’s through diversification within cropping systems or the exclusion and management of invasive species, urban ecology provides us with the tools to do better in the future.

Apple on a tree.
As urban trees die and need replacement, they can be replaced with fruit-bearing trees, such as this apple. Photo: Morguefile

As these ash trees die or get removed, they can be replaced with food-producing varieties of different fruit trees: cherry and apple, pear and mulberry. Not only are these food-producing trees beautiful when they bloom, but they provide pollen to the bees and other pollinators. The Beacon Food Forest of Seattle, Washington produced 4,250 pounds of food in 2017! That’s on just a portion of the proposed seven acres of land the forest will eventually encompass.

Rooftop garden.
This urban farm is on the rooftops of student-oriented apartment buildings in Berkeley, CA. The rooftops are connected by exterior walkways. Up to 16 tons of produce is harvested each year. Photo: TopLeafFarms.com.

Food forests aren’t the only way to integrate food production into the urban ecosystem. Small garden plots on empty lots and public land can be turned into community gardens. “Green” roofs can also serve as gardens and commercial greenhouses make up a thriving urban food production system that few of us hear about. Even your home garden can contribute to food production!

Urban food production might not feed the entire world, but it reduces the total miles driven bringing food to the city. This means less air pollution! It also helps to reduce food insecurity, and makes better use of the water we have transported and cleaned. Urban food provides verdant landscapes which soothe the mind surrounded by a jungle of concrete and steel. Food production impacts the city on many levels. Urban ecology influences how these resource decisions are made and how those decisions impact not only us, but also the plants and animals that inhabit those vibrant communities.


This article was sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Their members are researchers and trained, certified professionals in the areas of growing our world’s food supply, while protecting our environment. They work at universities, government research facilities, and private businesses across the United States and the world.

Sansevieria: The November 2020 Houseplant of the Month

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Photo: Thejoyofplants.co.uk, Styling by Elize Eveleens, Klimprodukties

The Story of the Sansevieria

The snake plant or sansevieria (Sansevieria trifasciata) is one of the world’s easiest and most widely grown houseplants and is also a common garden plant in tropical climates. The stemless plant produces thick upward-pointing, sword-shaped leaves with succulent properties. 

Sansevieria trifasciata
The common snake plant in its original form: Sansevieria trifasciata. Photo: @plant_wizard

The plant is called the snake plant because of its snakelike shape and markings and also mother-in-law’s tongue, because of its sharp tip, theoretically like sharp tongue of a critical mother-in-law. You may also hear the name bowstring hemp, because the tough leaves contain a fiber used in bowstrings, cordage, ropes, mats and nets.

Description

The coarse, fibrous leaves of the snake plant usually measure 28–35 in (70–90 cm) in height and 2 to 2 1/3 in (5–6 cm) wide, although under exceptional circumstances, they can reach over 6 ft (2 m) in height. Although flat towards the tip, at the base they are semicircular, fitting together in a tight rosette of usually 6 leaves. The leaves are dark green with distinctive light gray-green cross-banding. 

The plant spreads by producing new rosettes at the tip of thick rhizomes. Indoors, it fills its pot; outdoors in the tropics, it forms an ever-expanding mass of spiky greenery.

Sansevieria trifasciata flowers
The flowers are beautifully scented, but only at night. Photo: Lukáš Mižoch, Wikimemdia Commons

Flower are rare indoors and only appear on plants that receive abundant light. They appear on upright stalks and are whitish or greenish. They’re also highly perfumed, but only at night. The flowers are sometimes followed by small orange berries. Each rosette will only bloom once, but doesn’t die afterwards, but rather produces offsets that will flower in their turn.

Did You Know?

Side by side photos of Sansevieria trifasciata and Dracaena fragrant
Sansevieria trifasciata is now a dracena, like Dracaena fragrant. Who’d a thunk it? Photos: greenbayfloral.net & interiorfoliage.com

That the genus Sansevieria has been transferred to a new genus, Dracaena? This surprising change doesn’t make any sense to the average gardener, as the upright-growing, treelike or shrubby dracenas with their soft leaves (many people will know the corn plant, D. fragrans, for example) and the hard-leaved, rhizome-producing sansevierias, most with no visible above-ground stem, look nothing alike. But they share very similar flowers, both in appearance and in delicious nighttime perfume. And it goes to say that both are in the Asparagaceae family. 

For the purpose of this article, I’m sticking to the name Sansevieria, as on the market, they are only sold under that name, and hope that taxonomists will revise their reckoning. However, if you’re a hybridizer, maybe the two types could cross: imagine the possibilities!

Origin of the Snake Plant

The common sansevieria (S. trifasciata) is native to tropical Africa, from Nigeria to the Congo. The name Sansevieria honors the 18th-century scientist and inventor, Raimondo di Sangro, Prince of San Severo in Italy. It has been grown as a greenhouse plant for over 250 years, but only caught on as a houseplant in the 1920s when the famous department store chain, Woolworth’s, began offering it at only 5¢ per plant. Since it’s incredibly easy to grow and will put up with conditions that would kill most other plants, the snake plant has remained popular ever since.

Sansevieria Range

Sansevieria trifasciata ‘Laurentii’, with its yellow banded leaves
Sansevieria trifasciata ‘Laurentii’, with its yellow banded leaves, is one of the most popular cultivars. Photo: Mokkie, Wikimedia Commons

The snake plant has given a wide range of cultivars over the years, most starting as mutations from the original plant. The best known is Sansevieria trifasciata ‘Laurentii’, with long green leaves with a golden-yellow edge. ‘Bantel’s Sensation’, abundantly striped with white is fairly popular, as are ‘Moonshine’, with broader, shorter, silvery-green leaves, ‘Nelsonii’, with solid dark green leaves and no markings and ‘Black Gold’ with dark green leaves and transversal markings. Plus, there are many, many more of these “tall” sansevierias.

Bird's nest sansevierias ‘Hahni’ and ‘Golden Hahni’
Sansevieria trifasciata ‘Hahni’ (left) and ‘Golden Hahni’ (right) are bird’s-nest types. Photos: crocus.co.uk & logees.com

However, there is also another very different category: the bird’s-nest sansevierias. These derive from a mutation found in 1939 in New Orleans. Rather than tall, spearlike leaves that mostly grow straight up, these produce short, squat ones that arch a bit outwards, like a bird’s nest.

This first clone was called S. trifasciata ‘Hahni’ and has the same mottled coloration as the normal S. trifasciata, but many others followed, including ‘Golden Hahni’ with yellow bands along the leaf edges, ‘Silver Hahni’, with leaves heavily marbled in gray-green and ‘Black Dragon’, entirely dark green with no mottling whatsoever. 

Composite photo of Sansevieria trifasciata ‘Futura Simplex'
‘Futura Simplex’ is one of the most popular intermediate varieties. Photo: etsy.com

Then came the intermediate varieties, with broad leaves (up to 4 in/10 cm) half as long as the species, but still forming a sort of elongated, spreading bird’s nest. This includes the original, ‘Futura’, with gray-green marbling and a thin yellow edge, and a whole host of others, often mutations of ‘Futura’, such as ‘Futura Simplex’ with a broader yellow edge, or of ‘Robusta’, which is similar to ‘Futura’, but shorter.

You can usually find at least a few choices of all three groups (tall, intermediate and bird’s-nest) in most garden centers that sell houseplants.

Other Species to Try

Some 70 different species of Sansevieria are found throughout Africa, Madagascar and southern Asia. Many are grown as houseplants, but only a few have achieved any real popularity.

Sansevieria cylindrica, showing how leaves fit together in a fan at the base.
Cylindrical snake plant (Sansevieria cylindrica). The alternate leaves are inserted one into the other at the base, forming a fan. Photo: World of Succulents

Since around 2004, a different species, the cylindrical snake plant (Sansevieria cylindrica, now more correctly Dracaena angolensis), and also called African spear, has also become very popular. Its pointed leaves are tubular rather than flat. They are green with lighter transverse bands and set in a fan-shaped rosette. It’s generally a more compact plant that S. trifasciata, but still, some specimens have been known to reach 6 feet (2 m) in height. I find it easier to bloom than S. trifasciata.

Leaf cuttings of cylindrical snake plant, showing different forms, including braided and painted ones.
These aren’t plants, but just leaf cuttings of cylindrical snake plant. some possibly not even rooted at the time of sale. Photo: hillegom.nl & amazon.co.uk

The cylindrical snake plant is often sold in the form of leaf cuttings either placed symmetrically or braided. These curious forms are produced on an industrial scale in Thailand and other Asian countries. Of course, the cuttings eventually produce normal plants and the abnormal shape, whatever it was, will be lost. 

Sansevieria baculata leaf cuttings with offsets.
This pot of rooted Sansevieria baculata leaf cuttings is sprouting offsets. Photo: fromthegardenshed.ca

There are other species of sansevieria with cylindrical leaves, usually much thinner than those of S. cylindrica, including S. bacularis (sold as S. ‘Fernwood Mikado’).

Sansevieria ehrenbergii ‘Samurai Dwarf’
Sansevieria ehrenbergii ‘Samurai Dwarf’. Photo: secretgardenrareplants.com

And it doesn’t stop there! Some species are short and squat, others tall, some with broad leaves, others cylindrical, even more distinctly keeled. All seem easy to grow. Among those currently seen are S. ehrenbergii ‘Samurai Dwarf’ (‘Banana’) with a rosette of thick, short, boat-shaped leaves, the star sansevieria (S. kirkii), forming a flattened rosette of heavily marbled leaves, the whale fin or Mason Congo snake plant (S. masoniana) with often only one giant leaf flat leaf and one commonly called baseball bat (S. hallii) for its huge, thick, blue-green leaves that look like… you guessed it.

A Little Bit Poisonous

Sansevierias contain saponins which are mildly toxic to humans and pets (about as toxic as kitchen soap) and can lead to gastrointestinal upset if consumed, so keep them out of reach of pets or train them not to nibble on them. Serious poisonings are unlikely: the leaves are just too tough to ingest!

What to Look for When Buying Sansevierias

Variety of sansevierias including Sansevieria masoniana
A bit of a family portrait. The big leaf in the back is Sansevieria masoniana. Photo: @mulhalls
  • Size: Look carefully at the pot size and the thickness and length of the leaves. On some plants the pot may be somewhat distorted by the enormous strength of the underground rhizomes. This can sometimes even cause the pots to tear open. In that case repotting is an urgent necessity.
  • Leaves: On some varieties the way in which the leaves are trained or braided may be important to you. 
  • Health: Check that the plants are free of scale insects and mealybugs, corkiness or damaged leaf tips and that the roots are healthy. 
  • Rot: If sansevierias have been kept too wet for a long time they can suffer from rot. So, check that they are stable in the pot

Care Tips

Sansevierias are definitely low-care plants, ideal for beginning indoor gardeners.

Floppy sansevieria
In low light, sansevierias become floppy, messy and need staking. Photo: PhasmaUrbomach, reddit.com
  • You’ll hear all sorts of things about the light needs of sansevierias, but the truth is that they prefer very bright light and are not afraid of full sun. Bright light will always give the healthiest, happiest plants. And only in bright light will they bloom. That said, they are incredibly tolerant of negligence, including poor light, and will grow for years in spots so dark few other plants can survive. Growth will be slow and the leaves may be weak and need staking, but hey! At least they survive low light and that has to count for something!
  • Let the soil dry out between waterings, especially in the winter. Sansevierias definitely prefer to be too dry than too wet! Watering frequencies will necessarily vary according to conditions, from once every two weeks in bright light in summer to as little as once every 3 or 4 months under low light and cold conditions. When the soil is dry, do water, but do so thoroughly, moistening the entire root ball.
  • Sansevierias with thick leaves, like S. cylindrica and S. ehrenbergii, need even less water than those with fairly thin leaves, like S. trifasicata.
  • Do not pour water into the rosette of bird’s-nest sanseverias: they’re not bromeliads!
  • Their succulent leaves mean that sansevierias cope well with dry air. 
  • The plant does not require a dormant period in winter, but can take temperatures down to 40˚F (4ºC) if kept very dry, although a minimum of 55ºF (13ºC) is safer. 
  • The underground rhizome is incredibly strong and can distort and even crack the pot. Ideally, you’d repot it before it gets to that stage. 
  • Little to no fertilizer is required.
  • Repot as needed into a well-drained potting mix. Standard potting mix or cactus mixes are fine.

Multiplication

Variegated snake plant divided into sections for repotting.
Variegated snake plants can only by multiplied by division or rhizome sections. Photo: flowerpatchfarmhouse.com
  • Sanseverias are best multiplied by division of plants with multiple rosettes, usually done spring through fall. Sections of rhizomes will also produce more offsets. Only these two methods will allow most cultivars, especially variegated ones, to be true to type.
Leaf cuttings of variegated snake plant. All baby plants are without variegation.
Variegated sansevieria leaves will root, but the offsets won’t be variegated. Photo: Adela B.
  • Almost all will grow from leaf cuttings (even sections of leaves will do!) set into fairly dry soil, although the traits of many cultivars (especially variegation) will be lost, as many are chimeras and only come true from division. Cuttings may take months before showing any signs of life, but as long as the leaf remains green, offsets are likely to appear.
  • Sanseverias can readily be grown from seed, but this method is rarely used, because most will not be true to type (most cultivars will revert to the wild species). Also, it’s also a very slow method, taking years to produce a sizeable plant.

Did You Know?

That sanseverias are useful at filtering the air. The NASA Clean Air Study found S. trifasciata to be efficient in removing 4 of the 5 main toxins involved in the effects of sick building syndrome.

Display Tips for Sansevierias

Various sansevierias in similar white cache-pots.
A stunning collection of sansevierias in the same style of pot. Photo: blog.leonandgeorge.com 

People are increasingly seeking out nature and tranquility. Sansevieria fits perfectly with this with its simple clear shape. This can be emphasized by placing the plant in a mat cache-pot of a white or pale natural shade. Surprisingly enough, the effect is actually reinforced if the sansevieria is displayed as a “family” in the same style of pot. 

Feng Shui ( 風水)

According to Feng Shui principles, sansevierias bring good fortune into the home and ward off evil spirits. I find that to be only partly true. I’ve grown sansevierias for over 40 years and I still haven’t found fortune. However, I have not noticed any evil spirits hanging around either.

But do you really need Feng Shui as an excuse for growing sansevierias? I say just grow them because you like them!

Text partly based on a press release by Thejoyofplants.co.uk.

The Toxic Plants Garden: A Halloween Discovery

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A toxic tree, poison sumac (Toxicodendron vernix), rises above the Toxic Plants Garden in its striking Halloween colors. Photo: Jardin botanique de Montréal (Robert Mineau)

Here’s a bit of a Halloween theme: a garden of poisonous plants, a place where you might expect to find ghouls and goblins and miscreants of all sorts. There’s one at the Montreal Botanical Gardens, one of the world’s largest botanical gardens, with over 21,000 species. 

Map of Monreal Botanical Garden showing the location of the Toxic Plants Garden
The Toxic Plants Garden is just a very tiny corner of a huge garden. Ill.: Jardin botanique de Montréal

The Toxic Plants Garden, started in 1940 under the guidance of the Garden’s first curator, Henry Teuscher, is fairly well hidden, in a little rectangular section with walls and a fence right next to the Medicinal Plants Garden … a logical choice, since so many poisonous plants are used for medicinal purposes (think of foxglove [Digitalis purpurea], source of the heart medication digitalis and the opium poppy [Papaver somniferum] from which morphine is derived). There are signs warning you the plants are poisonous.

The objective of the Toxic Plants Garden is above all to present visitors with a sample of native, naturalized or cultivated species that visitors are likely to encounter in a garden or in a natural environment. Some of these species can cause poisoning following accidental ingestion of part of the plant or eating the fruits. Others can cause skin reactions or respiratory allergies. So, don’t touch them or even breathe in their pollen! Scary!

There are some 40 poisonous plants in the Garden, including poison ivy (Toxicodendron radicans), water hemlock (Cicuta maculata) and poison sumac (Toxicodendron vernix).

Castor bean plant
Ricin or castor bean (Ricinus communis) is a popular garden annual and a medicinal plant (remember castor oil), but also contains a deadly poison. Photo: Jardin botanique de Montréal (Michel Tremblay)

Some are of historical interest. Who doesn’t know that Socrates was killed by ingesting a decoction of poison hemlock (Conium maculatum) in 399 BCE, for example? Others made waves more recently: only a few weeks ago (September 2020), there was a ricin scare when a mentally unstable Quebec woman mailed a ricin powder tainted letter to the White House in an attempt assassinate the American President Donald Trump.

Not Such a Frightening Visit

Poison ivy with orange leaves
Fall colors of poison ivy (Toxicodendron radicans). Photo: Jardin botanique de Montréal (Pascale Maynard)

I’ve visited this garden many times and don’t find it at all lugubrious. Instead, it’s a charming little corner with some fascinating plants that you never see elsewhere. I mean, most botanical gardens would never think of growing poison ivy, yet it’s a highly attractive plant, with beautiful shiny leaves that change to spectacular fall colors.

If you’re an amateur botanist who wants to learn to identify some unusual plants, it’s also a great spot to do so. Where else will you find such a wide range of deadly, almost never grown plants in one place?

Poison hemlock with umbels of white flowers.
Poison hemlock: it looks just like a host of other umbellifers. They’re certainly not plants to experiment with! Photo: wnmu.edu

I enjoy looking at the venomous vegetation and trying to learn to recognize the individual plants, although I must admit that, to me, poison hemlock looks just like the sweet cecily (Myrrhis odorata) that I munch on all the time in my own garden. (Reminder to myself: if you find what looks like sweet Cecily in the wild, it’s best not to do a taste test.)

Giant hogweed seed cases.
Giant hogweed (Heracleum mantegazzianum). Note that is is a hogweed, not a hugweed: touching it can lead to severe skin irritation. Photo: Daniel Gélinas (Jardin botanique de Montréal).

It’s likewise a great place to take children. They find poisonous plants fascinating and will want to know all about just how the plants can kill. Supply as many gruesome details as you can: they’ll lap it up! I further recommend pretending to bite into an imaginary leaf, then clutching your throat, choking and falling to the ground as spasms take over your limbs and your eyes finally close in simulated death. They’ll love that! Of course, even as the visit titillates the morbid side of their nature, it teaches them not to put just any plant part in their mouth. And that’s a good thing!

Other Toxic Plants Gardens

The Toxic Garden at the Montreal Botanical Garden is not alone. There are others. Here are a few I know about:

The gate to the Poison Plant Garden at Alnwick Garden is certainly ghoulish enough! Photo: unbelievable-facts.com

The Poison Garden at England’s Alnwick Garden seems to get a lot more press than Montreal’s one and openly promotes its deadly denizens. It’s been called “the world’s most dangerous garden”: now, that ought to attract crowds! It’s a more recent garden, dating only to 1996, yet contains some 100 poisonous plants. I haven’t seen it, but I’d love to visit.

The Poison Garden at Blarney Castle. Photo: blarneycastle.ie

There is also a Poison Garden at Blarney Castle in Ireland, said to contain wolfsbane, mandrake, ricin, opium and cannabis, among other toxic plants. A warning sign says children must be accompanied by adults: a wise decision. It opened in 2010, the year after I lasted visited Blarney Castle, so I haven’t see this one either. (And no, I didn’t kiss the Blarney Stone!) 

The Orto Botanico di Padova is small (maybe condensed is a better word), but fascinating and well worth a visit. Photo: codiferro.it

The Orto Botanico di Padova (Padua Botanical Garden) in northwestern Italy, not far from Venice, which I have visited, dates back to 1545 and is best known for being the world’s oldest botanical garden that is still in its original location. It’s a UNESCO World Heritage Site and fascinating to visit, with its 16th-century buildings and dense, circular, systematic planting. It’s mostly dedicated to medicinal plants (the original purpose of botanical gardens was to bring together medicinal plants from all over the world) and plants are placed according to which of the four “humours” they were felt to belong, an old concept based on ancient Greek medicinal theory. The poisonous plants garden is off to one side. 

There may be other poisonous plant gardens. If so, let me know and I’ll share that information.

🎃 Happy Halloween … but do skip those hemlock bonbons! 

Help! My Bulbs Are Upside Down

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Even if you plant bulbs upside down, they won’t grow downward. Photo: pngfind.com, freepsdfilescom & wayfair.com

Question: I planted 40 tulip bulbs last month. Then I read you’re supposed to plant them with the pointed end up and the flat part down. I did the opposite! (It just seemed obvious to me that the point showed which direction you were supposed to plant the bulb!) I went out yesterday to dig them up and replant them the right way, but to my horror, the top (bottom?) of the first bulb I ran into was covered with roots and I didn’t dare move it for fear of damaging them. What should I do? Am I going to lose my tulips?

M. Khan

Answer: Don’t worry about it! Most bulbs have a flattened basal plate (basal meaning bottom) from which roots grow and a pointed side from which stems grow, so it makes sense to plant them with the flat end down and the pointed end facing up. But … if you plant them sideways or upside down, they’ll still grow perfectly well.

Tulip bulb upside down, roots on top and flower stalk redirected towards top.
An upside down bulb will send its flowers upward, not down. Photo: pngfind.com, freepsdfilescom & wayfair.com

Roots will appear from the basal plate, no matter what its angle, generally shortly after planting, and, in the spring, the flower stem, which will initially start growing pointing down, will quickly change direction and grow up. It reacts negatively to gravity and whichever way gravity tries to pull it, it will stubbornly grow the other way. This is known as negative gravitropism.

At worst, your upside-down tulip bulbs might be a tad shorter than normal, but even that isn’t a given.

And the bulb will correct itself the coming year. After a tulip bulb blooms, the mother bulb produces offsets or daughter bulbs: usually a big one that will replace her and bloom next year and smaller bulbs that help her reproduce and won’t bloom for a few years. The mother bulb then dies, her job done. However, the offsets that are formed will all grow the right way up, with the basal plate to the bottom and the point towards the sky. Ain’t nature wonderful?

Anemone tubers dry, in a box
With anemone tubers, you can’t tell which side is up anyway. Photo: Andrew Butco, Wikimedia Commons

This information applies to pretty much any bulb or bulblike organ. And that’s especially good news for those bulbs that don’t clearly have an up side or a down side, like the lumpy tubers of anemones (Anemone blanda and A. coronaria) and winter aconites (Eranthis hiemalis). You’ll never be able to guess which side goes up, so just plant them any old way.

Desperate to Grow Citrus? Try Trenching!

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Russians developed trenching techniques to grow citrus well beyond its normal range. Photo: lowtechmagazine.com

In a logical world, you’d grow citrus (Citrus spp., including oranges, lemons and mandarins) outdoors in an appropriate climate—in a tropical or subtropical area with winters on the cool side but frost free—and that would be the end of it. But humans always try to push the limits on everything, so you see citrus being grown on a huge scale in areas where frost does occasionally occur (leading to generalized panic and a media frenzy in those few years when frost does happen) and even indoors as houseplants where most produce no more than a few fruits per year. But the most extreme case I’ve heard of is growing citrus in trenches in cold climates.

This is not a technique for laidback gardeners. It’s extremely labor intensive and you have to be really keen to grow citrus to succeed with this. But in an article in Low-Tech Magazine (Fruit Trenches: Cultivating Subtropical Plants in Freezing Temperatures), writer Kris De Decker explains how the Russians, desperate for a local source of citrus fruits in the first half of the 20th century, pushed the limits of where they could grow citrus to the point where they were succeeding in places with truly cold winters: areas where temperatures could drop to -22 ºC (-30 ºC) and where the ground could freeze to a depth of 20 inches (50 cm).

This was never commercially viable, but that was not an issue in communist Russia. The country wanted to be self-sufficient in citrus production no matter what the cost. And it succeeded! From 1925, when citrus-growing was first introduced, until the 1950, the area consecrated to citrus-growing went from 0 to 74,000 acres (0 to 30,000 hectares), giving 200,000 tonnes of fruit, enough to make the country independent of fruit imports. Mandarins were the main crop, as they are fairly hardy, but oranges and lemons were also grown.

One technique used to push the culture of oranges further north was pruning the trees low to the ground to gain protection from ground heat. Ill.: lowtechmagazine.com

Various techniques were used to get citrus to grow beyond their normal range, including choosing and developing extra hardy clones, using dwarf and semi-dwarf trees pruned to remain low to the ground so as to profit from ground heat, planting on south-facing slopes and heavy mulching. But those would only bring in decent results in areas where winter temperatures dropped to no less than 5 ºF (-15 ºC). To go even lower took trenching.

Versailles Was an Inspiration

Gardens of Versailles with citrus in large pots and orangerie in the background.
The orangerie at Versailles is in the back. The rounded “shrubs” in containers are moveable citrus trees. Photo: Djampa, Wilkimedia Commons

That citrus could survive and thrive in temperate climates as long they were kept frost free had been known for centuries. At Versailles, in France, citrus have been grown in a special structure called an orangerie since 1686 and similar structures were common on large estates throughout Europe from the 17th to the 19th centuries until the introduction of modern greenhouses in the 1840s. There were even orangeries in Russia, including one at the Kuskovo estate in Moscow. 

Orangerie at the Kuskovo estate, Moscow. Photo; A. Savin, Wikimedia Commons

Orangeries are often considered greenhouses, but they aren’t covered in glass like a true greenhouse. Typically, they’re buildings with an opaque roof and thick walls on three sides that let in no light. One side, usually south-facing, has huge doors with glass panels so citrus plants in large pots, called Versailles planters, can be dragged indoors for the winter and put back outside for the summer.

Usually heated by coal-fired stoves that belched black smoke, the plants were soon covered in soot and thus received relatively little light. And temperatures were kept just above freezing.

However, for some citrus species, capable of tolerating near darkness and near-freezing temperatures for 3 to 4 months a year (not something most truly tropical plants can take!), that was enough to keep them alive and productive. And also to please the chateau’s owners, who could put exotic fruits on their table to impress guests.

Citrus Trenches

By the 1940s, trenching had really pushed the limits of where citrus could be grown in Russia into areas with truly cold, snowy winters. 

Drawing of two trenches protected for the winter.
Trenches protected for the winter. Ill.: ;owtechmagazine.com

Trenches were dug from 30 inches (80 cm) to 6 feet (2 m) deep, depending on how deep frost could be expected to extend into the soil in a given region. They were oriented from east to west for optimal sunlight during the winter and angled slightly to catch more light. Obviously, special care was also needed to permit good drainage. 

Drawing of a trench showing its winter insulation.
Drawing of a trench showing its winter insulation. Ill.: lowtechmagazine.com

Dwarfed and low-pruned citrus were planted permanently in the bottom. Glass covering was expensive, so was used sparingly, only a few sections here and there to provide some light and even then, covered with straw mats when necessary. Otherwise, the trenches were instead covered with thick boards, then straw mats for extra insulation. The covering would be raised or removed on days when temperatures were above freezing and put back into place at night.

Free trade and the resulting easy access to inexpensive citrus from other countries has wiped out citrus trenching on an agricultural scale after the collapse of Soviet Russia. But some Russians still grow their own citrus in trenches at their dacha to this day.

If you want to try citrus trenching, go for it! But if you live in a climate too cold for citrus, might I suggest instead following the Versailles model and just bringing your citrus indoors for the winter, then putting them out for the summer. That somehow seems a lot easier!

Lichens on Trees? Not to Worry!

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Lichens are often found on trees and are not harmful. Photo: Neil Sperry, theeagle.com

When trees lose their leaves in the fall, you sometimes discover crusty or fibrous grayish or milky green growths on the branches and trunks of your trees. These are not fungus, but lichens: composite, symbiotic organisms formed by the association of algae or cyanobacteria and a filamentous fungus. You’ll also see lichens on rocks and sometimes on the bare ground. And while ghostly gray and muddy green are their main colors, they can come in all sorts of shades, even bright oranges, yellows, yes, even pink!

In no way are tree lichens harmful to the bark on which they grow. They are strictly epiphytes, that is, organisms attached to the outside of the bark. They are not parasites (which, by definition, harm their host) and seek nothing from the tree other than a support on which to grow.

Benefits of Lichens

Lichen on apple tree bark.
Lichen on the bark of an apple tree. Photo: extension.unh.edu

Lichens are even considered beneficial.

First of all, they make interesting pollution indicators, as they won’t grow in polluted air. If lichens start to grow on your trees, that’s good news: a sign that the air is fairly pure! In fact, lichens are moving back into cities after decades of absence as air quality improves compared to what it was in the 1970s and 1980s, back when leaded gas and industry chimneys belching toxic smoke were the norm.

Also, lichens have the capacity to absorb nitrogen directly from the air. When it rains, some of this nitrogen trickles down to the roots of the host tree, helping it grow better.

Hummingbird nest covered in lichens
Baby ruby-throated hummingbird in its nest made of lichen. Photo: google.com

Many birds—including hummingbirds!—use lichens to build their nests.

Also some animals feed on lichens, including reindeer and caribou (caribou moss, the main winter food of caribou, is actually a lichen: Cladina spp.), but also many others.

Finally, indigenous peoples all around the world use lichens in medicinal treatments and in preparing dyes. Some lichens (but not all!) are even edible!

Disadvantages of lichens

Various lichens on a branch
A mixture of lichens on a branch. Photo: courierpostonline.com

There aren’t any.


The belief that lichens kill tree branches is an old myth. True enough, lichens are often numerous on old, weak or dying branches, but it’s not the lichens that are killing them. Lichens have just settled in because there is less leaf coverage on those branches and they need sunlight in order to grow. 

Dead tree covered in lichens.
Dead tree covered in lichens. Photo: Walter Baxter, Wikimedia Commons

The presence of abundant lichens on a tree could indicate that it’s in decline, with a less dense leaf covering than it should normally have. If so, don’t blame the lichens, but give the tree better care. You could try fertilizing it modestly and watering it in times of drought. Or if there is a drainage problem, fix that. And sometimes trees just die and nothing can be done to save them. That’s just something that you, as a gardener, have to learn to accept. 

But while lichens may warn of a problem. they aren’t the problem. So, don’t shoot the messenger!

What Should You Do?

Normally, if you find lichens growing on one of your trees, you should simply leave them alone. Think of their presence as a sign to visitors that nature is welcome in your garden.

If you simply cannot tolerate the presence of lichens, just rub the bark with a soapy brush to knock them free. Rub gently, being careful not to damage the bark or dormant buds.

And no, fungicides won’t kill lichens, so don’t waste time spraying them. After all, lichens aren’t fungus, are they?

Article adapted from one published on October 17, 2015