How Oaks and Beeches Control Their Predators


During a mast year, squirrels find more acorns than they can eat. Ill.:, montage:

Squirrels, jays and other nut-eating animals like nothing better than fattening up on acorns, chestnuts and beechnuts in preparation for winter. They’re rich in oils, protein and carbohydrates, as well as calcium, phosphorus, potassium and the vitamin niacin. Not only do nut-munchers stuff themselves on the nuts, they bury countless others for future eating… then either forget to dig them back up or finally don’t use them, as they typically hide far more than they’d need when the harvest is good. Thus, they actually plant future beech, chestnut and oak forests, bending to the will of the trees.

Population Control

And oaks, chestnuts and beeches are even craftier than you might think. If they produced equal numbers of nuts every year, the squirrel and jay population would remain high and they’d consume most of the fallen nuts. Instead, they have “mast* years”: years in which they produce huge quantities of nuts, far more than their predators could possibly eat, followed by several to many years of slim pickings. This keeps the squirrel and jay population relatively low. 

*Mast: name for the fruit of beeches, oaks, chestnuts and other woodland trees.

How? When a mast year occurs and thus food is plentiful, there aren’t that many nut predators around, as they’ve gone through several low-nut winters in a row. The winter and summer following a mast year, since food is plentiful, many more predators survive the winter and the forests fill with squirrels and jays. But the following winter, after a skimpy harvest when there’s little to eat, fewer squirrels and jays survive. And several years in a row of low nut production really keep the population in check. Mast years occur every 3 to 15 years, depending on factors yet unknown.

And the off years, when few nuts are produced, allow the nut trees to store up more energy for the next mass year.

Coordination Is the Key

Of course, this wouldn’t work if each oak, chestnut and beech in the forest were on its own schedule and thus there were always trees having a mast year each fall. Instead, the trees somehow collaborate locally. All the nut trees in a given region will have their mast year all at once, followed by several coordinated years of low production. 

It’s possible trees communicate with each other to coordinate a mast year. Ill.:

How do the trees coordinate their mast years? That remains a mystery. Perhaps there is a climatic signal of some kind that indicates that a certain year would be a good one to hold a mast year. Others theorize that the trees actually communicate with each other, not in words, but by sending signals from tree to tree via their roots. (“Hey, guys! We’ve been taking it easy for the last six seasons, storing up our energy. Why don’t we make this year a mast year!”)

Whatever the reason, mast years have been recognized by foresters (and nut harvesters) for generations, but it’s only recently that the reason behind them – over- then under-producing to control predators – has been studied. 

Ain’t nature wonderful!


Underpot to Keep Indoor Trees Under Control


Do you really want your indoor trees to reach the ceiling? Photo:

Indoor trees are marvelous things. They give you the feeling of being in the great outdoors even while you’re in your own living room. They provide shade, making reading easier, they help purify the air and they perk up your décor like nothing else. But they do tend to get big over time. Ficus, scheffleras, money trees, corn plants and other indoor trees just want to keep growing. In nature, some can reach 50 feet (15 m) or more in height. That’s just not possible indoors. So, what’s an indoor gardener to do?

Benign Neglect

Once your indoor tree (here, a Ficus benjamina) has reached the size you want, slow it down by no longer potting it into bigger containers. Photo: Julie Deken,

One thing you can try that requires very little effort on your part is to simply stop potting them up. That is, start leaving them in the same pot year after year instead of moving them to a bigger one every two to three years, as you’ve been told you ought to do. With their roots severely constrained, most trees wisely start to grow more slowly, some putting on almost no new growth worth mentioning, but simply replacing older leaves with fresh ones. 

Severe underpotting has helped keep this nearly 400-year old bonsai small. Photo: Ragesoss, Wikimedia Commons

Underpotting in this manner has been used in producing bonsais, tiny, pot-bound replicas of full-sized trees, for 2,000 years. On indoor trees, you simply apply it at a later stage, when they’ve reached the size you want.

Now, depending on the species, some selective pruning may also be needed, cutting back taller branches to stimulate denser, shorter growth, but by the time a tree has been in the same pot about three years, you’ll find you won’t need much of it. Underpotting will have slowed it down considerably.

Saves Time, Effort and Cash!

Repoting a large plant is a lot of work. Do you really want to do it? Photo:

Besides, repotting a big plant is a major hassle. They’re heavy and awkward to manipulate. Just getting the old pot off without a second pair of helping hands can be a struggle! If you keep the plant in the same pot year after year, you avoid that.

Plus, you save the price of fresh soil and the cost of a new, bigger pot. OK, admittedly, potting soil is not that expensive, but pots—certainly big pots suitable for an indoor tree—certainly can be.

What About Mineral Salt Buildup?

Mineral salt buildup inside a pot. Photo:

One of the reasons for repotting houseplants has always been to reduce the buildup of mineral salts, deposits caused by the use of hard water and fertilizer that have high concentrations of dissolved substances such as calcium carbonate, sodium, and iron. They’re often visible as a sort of white to yellow crust forming on the inside of the pots and are a sign the potting mix is becoming slowly toxic to the plant. By repotting into a larger pot, thus changing part of the old growing mix and adding fresh, uncontaminated mix around the root ball, you can help alleviate that. 

So, what happens if you’ve stopped moving your tree into bigger and bigger pots. Won’t the mineral salts build up until they kill them?

Not if you try one (or both) of two things: leaching and top dressing. 

In leaching, you pour fresh water over the soil until it drains out the bottom. And keep it up until you’ve applied the equivalent of two to three times the pot’s volume. That will dissolve and carry away much of the minerals. Then you simply throw away the drainage water. 

It’s easy enough to leach a small houseplant in the kitchen sink, but trees may need to be leached outdoors. Ill.: Claire Tourigny, from the book Les 1500 trucs du jardinier paresseux

Leaching a tree while it’s indoors is pretty much impossible, though. It’s not as if you can put it in a kitchen sink to leach it as you would for a smaller plant. And it may no longer fit into the shower. I leach my indoor trees simply by putting them outdoors for the summer without a saucer underneath. There, Mother Nature does the leaching by supplying regular downpours. In a drier climate, simply water more than strictly necessary and the leachate will drain off, carrying the excess minerals away. 

Top dress by scraping off the top layer of potting soil and replacing it with fresh mix. Ill.: Claire Tourigny, from the book Les 1500 trucs du jardinier paresseux

To top dress, just scrape off the top layer of soil (about an inch/3 cm or so) annually and drop it into the compost pile. That works because mineral salts tend to migrate upwards and mainly accumulate in the top part of growing mix. By removing the top layer of soil, you’ll severely reduce mineral salt buildup … and all that’s left to do is to replace the inch (3 cm) of soil removed with an equal amount of fresh potting mix.

How Long Can You Delay Repotting?

But how long can you keep this underpotting thing going? 

Actually, I don’t know the upper limit, but I have some fairly imposing corn plants and ficuses that haven’t been repotted in 20 years and they’re still doing fine just through leaching them outdoors in the summer and annual top dressing. And remember 400-year old bonsais in their tiny, root-cramped pots. 

I therefore figure there is probably no real upper limit. You can just keep not potting up pretty much forever.

So, slow your trees down by not repotting them, a laidback solution to a common houseplant problem!

Why is My Echinacea Turning Green?


First the disease affects echinacea’s cone, causing green growth to appear. Photo:

Yes, there are a few plants with green flowers: green roses, green zinnias, green glads, green echinaceas, etc. These plants are hybrids developed for their unusual color. But if a plant you choose for flowers of another color suddenly starts producing green flowers, the chances are pretty good it is suffering from a disease: aster yellows.

Aster yellows is a very common in the wild, found especially in goldenrods, asters and other wildflowers, and is caused by the aster yellow phytoplasma (AYP), a bizarre entity closely related to bacteria, but behaving like a virus. Notably, once a plant is infected, no treatment can cure it. 

Leafhoppers transport aster yellows from one plant to another. Photo:

Aster yellows are transmitted by leafhoppers: by piercing plant tissues, they inject the phytoplasma which then extends gradually throughout the plant, affecting its growth and gradually weakening it.

Over time, the entire flower turns green and often begins to produce satellite flowers. Photo:

The first symptom in many plants is the greening of the flowers. This is called phyllody, the abnormal development of floral parts into leafy structures. In the case of echinaceas, a kind of green growth starts to form on the cone in the flower’s center. Over time, the cone produces small satellite flowers that are completely green. Weird … and really not too wonderful!

The only treatment for aster yellows is to destroy the plant. If left alive, the disease will gradually spread to neighboring plants, including echinaceas, asters, carrots, cosmos, strawberries, daisies, marigolds, zinnias. More than 300 other plants in 84 different plant families are known to be infected by this disease.

This is a case where a quick strike solves a ton of future problems: yank the infected plant out at the first sign of symptoms and you can prevent the disease from spreading to your other garden plants.

Article originally published on September 27, 2014. 

Mini Horticultural Myth: Dormant Bulbs Need Darkness


Sleeping bulbs are indifferent to light. Ill.:, &, montage:

I want to bring up a very minor detail on the cultivation of tender bulbs (gladioli, cannas, dahlias, tuberous begonias, etc.), but one still worth clarifying: the concept that bulbs need darkness during their dormant period.

Typically, the explanation offered to gardeners is that when you bring tender bulbs indoors, you need keep them in a spot that is cool, dry and dark, such as a basement, a slightly heated garage or a root cellar. But in fact, darkness itself is not a factor.

When a Bulb Is Sleeping

As long as you keep dormant bulbs dry (and, for many, cool as well), they don’t care about the lighting conditions. Photo:

Dormant bulbs are just that: dormant. They’ve stopped all growth. And when they’re in that state, they’re perfectly indifferent to light. Sun, partial shade, darkness: it’s all the same to them. True enough, you don’t want to store them in a spot that gets really hot as that could cause them to dry out and intense sun can indeed heat things up quite a bit. However, if you have potential storage space that receives light part of the day or even all day, yet remains cool, that would be a perfect place for bulbs.

Other Dormant Plants Too

Also, the same information applies to any plant that goes dormant at some time during the year: amaryllis, cyclamens, desert cacti, etc. Yes, do stop watering them and yes, do put them in a cooler place … but there is no need to keep them in the dark unless there is some reason that would be convenient for you.

I tried to come up with even one exception: a single plant that must necessarily experience darkness 24 hours a day for a long time when it is dormant, but I couldn’t think of one.

And, when you think this over, this is quite logical: when a plant goes dormant in the wild, it doesn’t dig itself up and take refuge in a dark cave nearby. It stays where it is and puts up with whatever natural light is found in that spot.

So, if there is a window in the garage or basement where you overwinter your bulbs, you don’t need to block it nor to seal the bulbs in an opaque box. As long as this light doesn’t overly heat the room, its presence or absence is irrelevant.

No Mess Crabapples


‘Indian Summer’ is one of the small-fruited crabapples that provide spectacular winter color without requiring a massive cleanup. Photo:

Gardeners love crabapples (Malus species) for their spectacular spring flowers and attractive berries … until the latter start to drop on their decks, lawns and walkways in the fall. Having to slip and slide over rotting fruits as you head off to work each morning is unpleasant and even dangerous. And imagine all the work involved in cleaning up the icky mess!

However, if you choose the right crabapple, this situation can be avoided, as there are both “messy” and “clean” varieties of crabapple.

The messy crabapple varieties bear relatively large and juicy fruits. Birds peck at them, but never swallow them: they’re too big. Because of the fruits’ weight, they fall readily from the tree and cover the ground with a slippery mess.

When it comes to small-fruited crabs, just let the birds do all the work! Photo: Dave Maslowski,

Other varieties, though, produce tiny little crabapples that aren’t as juicy and tend to remain on the tree. In fact, small crabapples usually persist throughout much of the winter (for a very nice effect on a background of white snow, by the way!). And when birds visit the tree, usually towards the end of winter when crabapples are at their sweetest (cold slowly converts their starches into sugars), they swallow the tiny crabapples whole. So they end up cleaning the tree from top to bottom before spring, leaving few berries on the ground! And any they miss aren’t “squishy.” That’s why tiny-berried crabapples can be said to be “clean.”

Some crabapple varieties, though, are clean for another reason: they are essentially sterile. In other words, they produce a lot of flowers, but almost no fruit. In the following list, the latter are indicated by an asterisk (*).

Clean Crabapples for Home Gardens

1. Malus ‘Adams’ (zone 4-8)

2.     M. ‘Candied Apple’ (zone 4-8)

3.     M. Centurion® (‘Centsam’) (zone 4-8)

4.     M. ‘David’ (zone 4-8)

5.     M. ‘Donald Wyman’ (zone 4-8)

6.     M. ‘Firebird’ (zone 4-8)

Harvest Gold crabapple looks like it is decorated with tiny Christmas lights! Photo:

7.     M. Harvest Gold® (‘Hargozam’) (zone 3-8)

8.     M. ‘Indian Magic’ (zone 4-8)

9.     M. ‘Indian Summer’ (zone 4-8)

10.  M. Lancelot (‘Lanzam’) (zone 4-8)

11.  M. ‘Liset’ (zone 4-8)

12.  M. ‘Louisa’ (zone 4-8)

13.  M. ‘Madonna’ (zone 4-8)

14.  M. ‘Makamik’ (zone 2b-8)

15.  M. Marilee® (‘Jarmin’) (zone 4-8)

16.  M. ‘Maybride’ (zone 4-8)

17.  M. ‘Molten Lava’ (zone 4-8)

Malus ‘Pom’zai is the smallest of the crabapples, scarcely more than a shrub. Photo: Impatience-1, flickr

18.  M. ‘Pom’zai (‘Courtabri’) (zone 4b-8)

19.  M. ‘Prairie Rose’ (zone 4-8)

20.  M. ‘Prairifire’ (zone 4-8)

21.  M. ‘Professor Sprenger’ (zone 4-8)

22.  M. ‘Profusion’ (zone 4-8)

23.  M. Raspberry Spear™ (‘JFS KW213MX’) (zone 4-8)

24.  M. ‘Red Jade’ (zone 3-8)

If anything, small-fruited crabapples (here Malus Red Jewel) look even better when coated in snow, frost or ice. Photo:

25.  M. Red Jewel™ (‘Jewelcole’) (zone 4-8)

26.  M. ‘Red Splendor’ (zone 3-8)

27.  M. ‘Robinson’ (zone 4-8)

28.  M. ‘Royal Beauty’ (zone 3b-8

29.  M. Royal Raindrops® (‘JFS-KW5’) (zone 4-8)

30.  M. ‘Rudolph’ (zone 2-8)

31.  M. sargentii (zone 5-8)

32.  M. sargentii ‘Tina’ (zone 5-8)

33.  M. ‘Sir Lancelot’ (zone 3-8)

‘Snowdrift’ crabapple is just as striking in fruit as it is in bloom. Photo:

34.  M. ‘Snowdrift’ (zone 4-8)

35.  M. ‘Spring Snow’* (zone 4

Malus Sugartyme is a personal favorite of mine. Photo:

36.  M. Sugartyme® (‘Sutyzam’) (zone 4-8)

37.  M. ‘Thunderchild’ (zone 3-8)

38.  M. ‘White Angel’ (zone 2b-8)

39.  M. × zumi calocarpa (zones 4-8)

Adapted from an article originally published on October 8, 2014.

Growing Figs in a Cold Climate


‘Chicago Hardy’ fig tree, 2 years old, grown in a pot for easy indoor/outdoor movement. Photo:

Email Message: I grow a dozen varieties of fig trees (Ficus carica) in hardiness zone 5, far too cold for most figs (they’re normally hardy only to zone 7 or 8). Most are hardier varieties obtained from Richters Herbs in Ontario, ordered via the Internet and delivered to my home. I also have two plants that I bought in, of all places, the seasonal garden center of my local supermarket! I get two harvests each year: a first yield in July and a second at the end of September.

I grow these fig trees in pots and bring them into my garage for the winter after they’ve lost their leaves. That way, they remain cold, but without freezing and are thus kept fully dormant. Then I put them back outside as soon as they start to come out of their dormancy in mid-April. 

Dormant fig laid in a trench and ready for winter. Photo:

You can also lay them in a trench in the garden in late fall and cover them with earth or straw for the winter, then replant them in the spring.

It’s a lot of work! But for the joy of eating figs that you’ve grown yourself, it’s worth it!

Marcel Pedneault
Pontiac, Quebec
(Just north of Ottawa)

Response: Thank you for your comment. 

Personally, when I was a young gardener and ready for any horticultural challenge, I also tried growing hardy figs … in zone 4 (even a bit colder than your region)!

I tried the same two methods, but I must admit that I found it to be a lot of work, especially the trick of burying a quite sizable shrub in a trench for the winter. I only did that once: what a herculean effort! 

After I’d enjoyed a few light, but delicious harvests via the “cold storage” method (having no garage, I used my root cellar), I decided that lugging the increasingly heavy fig trees down to the basement, then back up the stairs to their summer home outdoors was just too much effort. When I realized the fifth fall that I would have to get my neighbor to come over and help me move them, that was enough! I just let them die a natural death: a harsh winter outdoors.

I prefer my gardening slow and easy! Ill.: Claire Tourigny, from the book Les 1500 trucs du jardinier paresseux

I concluded that, in the end, I prefer fruit trees and shrubs better adapted to my climate, ones that can be grown without any special effort, that I can just plant and let grow on their own, like blueberries, disease-resistant apples and haskaps (honeyberries)*. Those are my kind of fruits! (If I call myself the laidback gardener, it’s not for nothing!)

*These fruits are no-brainers under my growing conditions, but what grows readily in yours might be quite a different selection!

But for gardeners more hard-working than I am, it’s true that raising exotic fruits in a climate where they normally can’t be grown is quite a thrill! So, keep up your enthusiasm … and the good work!

Never Lose a Dahlia Name Again!


Just write the cultivar name on the tuber so you won’t forget it! Photo: Swan River Dahlias

You’ve started to build up a nice collection of dahlias: ‘Bishop of Llandaff’, ‘Kelvin Floodlight’, ‘Night Butterfly’, etc. In the garden, each is clearly distinct: the flowers are of different colors, different shapes, different sizes, even the size of the plant itself varies. There is no risk of confusion. But in the fall, when you dig up the tubers in order to store them dormanct indoors for the winter? Or in the spring, when you go to plant them? Well, you have to admit it: without their flowers and leaves, all dahlias look pretty much alike!

Obviously, you can write the cultivar name on a plant label and place it with the tubers of that variety when you store them for the winter. But labels have an unfortunate tendency of falling off, becoming misplaced or even disappearing entirely. And it only takes a few seconds of distraction to totally forget which dahlia is which. 

The result? A whole series of unnamed dahlias you’ll probably never be able to correctly identify. What confusion!

So, why not solve the problem the simple way and just write the name of the cultivar directly on the tuber?

The tuber should be dry and relatively clean. Take an indelible marker (one designed for garden use is best; I find standard Sharpies smear all too readily!) and write the name on the tuber. In spring, when it’s time to plant the tuber for a new season, its cultivar name will still be perfectly legible (even if the tuber is now a bit shriveled) and you’ll immediately be able to distinguish it from the other varieties!