Plant More Than Milkweeds to Save Monarchs

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The enigmatic monarch butterfly is having a hard time surviving. Source: LyWashu, Wikimedia Commons

In North America, the serious decline of the monarch butterfly (Danaus plexippus), the black-veined orange migratory butterfly that winters in Mexico and California and travels all the way to Canada in the summer, has been highly publicized. It’s hard to imagine of anyone who hasn’t heard about it. Its population has been declining for at least 50 years, and since 2008, the population has dropped dramatically, from 1 billion to 93 million butterflies. That still sounds like a lot of butterflies, but if the population keeps dropping at this rate, within a generation this emblematic butterfly will no longer grace our fields and gardens.

Several authorities attribute the decline to modern agricultural practices, especially the widespread use of herbicides (deadly to milkweeds, the unique food of monarch caterpillars), as they create vast surfaces where nothing but the crop in question (maize, soybeans, etc.) grows. Monocultures stretching as far as the eye see offer neither food nor shelter to migrating monarchs.

In addition, several years of climate disruption in Texas, a state through which almost all the monarchs in eastern America have to pass, including severe droughts and unseasonable frosts, have aggravated the situation. As have the illegal cutting of forests in Mexico where the butterflies spend several months in winter dormancy and the indiscriminate use of insecticides everywhere along their route.

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There are programs all over North America teaching people what they can so to help protect monarch butterflies. Source: planobluestem.blogspot.ca

In recent years, associations have appeared throughout North America that seek to protect monarch butterflies. Most have developed some sort of program that asks home gardeners to “do their share” and offer an oasis for monarchs on their lot: a garden often called a monarch way station, somewhere monarch butterflies will not only be tolerated, but actually encouraged.

The principle is certainly simple enough: monarch butterflies need flowers in order to survive, so if enough people create flower beds all along the route that butterflies follow from Mexico to southern Canada, that should help the monarch population to recover!

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A monarch caterpillar munching on the leaf of a butterfly weed (A. tuberosa). Source: Marshal Hedin, Wikimedia Commons

Especially put forward is the idea of planting milkweeds (Asclepias spp.). Indeed, monarch larvae (caterpillars) can only feed on milkweeds (and plants of the related African genus Gomphocarpus): they have no other source of food. They’ll die if offered anything else. Plant a milkweed, save a butterfly: it certainly sounds simple enough.

No Sooner Said Than Done!

Gardeners definitely understood the last point. They are planting more milkweeds. The sale of milkweeds, once rather obscure plants, is booming in Canada and the United States: everybody seems to be planting them, notably with school teachers pushing the idea in the classroom and kids asking their parents to plant them … and that’s great. Every little effort helps. But planting milkweeds is not going to entirely solve the problem: it’s a bit more complicated than that.

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Monarch butterflies feed on the nectar of a wide range of flowers, not just milkweeds. Here they’re feeding on wild ageratum (Conoclinium coelestinum). Source: pxhere.com.

Just as important as planting milkweeds to feed larvae is planting and maintaining nectar plants for adult butterflies. Adult monarchs, in fact, are not in any way limited to milkweed flowers, but instead feed on a wide range of nectar-rich blooms. They need plants in bloom as a food source whenever they’re in a given region. That is, from spring through late fall in the south and in the summer and very early fall in the northern part of their range.

Storing Up for the Return Trip

It is especially important to offer an abundance of nectar-rich flowers in late summer and in fall. Here’s why:

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The monarch’s migration: step by step. Source: askabiologist.asu.edu

Contrary to their spring migration, which is multi-generational (monarchs migrate in stages, stopping on their way north to lay eggs at different points and produce new butterflies that will complete the route to the North, and therefore milkweeds are essential for feeding the caterpillars of the up-and-coming generation), the return from the North to the South is done in a single generation. The same butterfly born in the summer on a milkweed in, say, Northern Ontario, at the extreme northern edge of the monarch’s range, has to fly all the way to the heart of Mexico, a distance of about 3,000 miles (4,800 kilometers). Before it leaves, at summer’s end, it needs to stock up on lipids (fats) that will help carry it down to Mexico. Then all along its route south, it needs to stop regularly to feed on flowers rich in nectar.

Note that milkweeds (Asclepias) are not at all necessary on the return trip and at any rate, most will have finished blooming by then. Monarchs don’t need milkweeds in the fall, because the females will not be laying eggs on their way south, nor will there be any caterpillars that need to feed on milkweed leaves. Actually, it won’t be until March or April of the following year, when monarch butterflies wake up after their winter dormancy and start to fly north, that they need to find milkweeds on which to lay their eggs. Instead, southward migrating monarchs need other nectar-rich flowers: late-blooming ones.

This is such an important factor that some scientists believe that to try to boost the monarch population, planting milkweeds is considerably less important than preserving and planting late-blooming flowering plants! (See the study done by Cornell University: Linking the continental migratory cycle of the monarch butterfly to understand its population decline.)

Create Your Own Monarch Oasis

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A garden designed as a monarch oasis. Source: esusbranch.wordpress.com

If you want to create a monarch garden on your lot or organize one at your school or in a local park, here are some considerations:

  1. Ideally, it should be in full sun in a spot protected from the wind.
  2. It should contain milkweeds (Asclepias spp.) to feed the caterpillars in the spring (southern locations) and in early to mid-summer (elsewhere), as well as a good variety of nectar-bearing flowers to feed the adult butterflies throughout the summer and into fall.
  3. The larger the flower bed, the more it will be used. (Do you really need the vast sea of green lawn that surrounds most houses and that is the equivalent of a monarch butterfly desert?)
  4. You have to learn to accept a bit of imperfection in a butterfly garden. Yes, some leaves will be munched on: the caterpillars need to eat something! And there will probably be less attractive insects on your milkweeds (they do have their share of insect pests) you’d do best to learn to ignore.
  5. Avoid treating your butterfly garden with products toxic to butterflies, such as insecticides. If you feel you have to treat plants in the garden, prefer gentle treatments like a sharp spray of water or hand picking. Even organic insecticides, likes insecticidal soap and neem, can harm caterpillars and butterflies.

Plants That Feed Monarchs

To feed monarch caterpillars, it’s essential to include milkweeds in your monarch oasis.

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The two most common perennial milkweeds in garden centers: butterfly weed (Asclepias tuberosa), left, and swamp milkweed (Asclepias incarnata), right. Source: Derek Ramsey, WC & http://www.robsplants.com

Butterfly weed (A. tuberosa), zone 4, with orange or yellow flowers, and swamp milkweed (A. incarnata), zone 3, with pink or white flowers, are the easiest to find in plant nurseries. The first prefers very well-drained to dry soils, while the second is better adapted to average garden soils, which are richer and more humid.

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Common milkweed (Asclepias syriaca) is a weedier species you may not need to grow if it is common in your area. Source: Stefan.lefnaer, Wikimedia Commons

In eastern North America, common milkweed (A. syriaca) is already widespread in the wild, as is its western equivalent, showy milkweed (A. speciosa), in its territory. Neither are widely available commercially and can be a bit invasive in a flower bed.

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Tropical milkweed (Asclepias curassavica) is a good container plant. Source:  Jeevan Jose, Wikimedia Commons

Gardeners in mild climates and those limited to balcony and patio gardening could try tropical milkweed (A. curassavica). It will grow as a perennial in zones 9 to 11 and in pots as an annual in colder climates.

There are some 140 other milkweed species, but the commercial distribution of most is very limited.

Nectar Plants

So, you’ve planted milkweeds to feed monarch caterpillars. Now you have to nourish the adult butterflies. For that, you need a good variety of plants that produce abundant nectar. Milkweeds do work, but likely won’t be enough. You need plenty of flowers of all kinds.

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Monarchs prefer clustered flowers, like those of ‘Herbstfreude’ sedum (Hylotelephium ‘Herbstfreude’, syn. Sedum ‘Herbstfreude’). Source: Darkone, Wikimedia Commons

Butterfly plants usually produce inflorescences with clustered flowers, such as are found in the Asteraceae, Apiaceae and Verbenaceae families. Either loose clusters, like lantanas or verbenas, or dense flower heads, like rudbeckias and echinaceas, will do. The latter even come with a butterfly landing platform, the ray flowers (their so-called petals) that surround the flower head. Butterflies generally find individual flowers less attractive.

Brightly colored flowers attract monarchs, but they are relatively indifferent to perfumes (except for the fragrance of milkweeds, which they can detect from a great distance). Beware of double flowers: sometimes, but not always, the extra petioles render the nectar inaccessible to monarchs.

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Don’t be afraid to mix imported flowers with native ones: studies show this attracts more butterflies. Source: charismaticplanet.com

The traditional belief that you should choose strictly native flowers for your monarch oasis is now considered erroneous: recent studies show that a mixture of native and imported flowers attracts and feeds the most butterflies.

Later Bloomers

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Late-blooming nectar plants, like this Canada goldenrod (Solidago canadensis), are the most important suppliers of pollen for the monarchs’ trip back to Mexico. Source: Harry Rose, Wikimedia Commons

At the end of the summer, things start to get serious. Monarchs will need to drink a lot of nectar to accumulate good reserves, essential for their flight south. Thus, the utility of nectar-rich flowers increases as summer winds down. The list below concentrates on plants that will be in bloom from mid-August on, the time of year when monarchs need nectar the most:

  1. Ageratum (Ageratum spp.) — annual
  2. Ageratum, Hardy (Conoclinium spp.) — zones 5–10
  3. Alyssum (Lobularia × hybridum) — annual or zones 9–11
  4. Aster (Aster spp., Symphyotrichum spp. and several other genera) — zones 2–9
  5. Balloon Plant (Gomphocarpus spp.) — annual or zones 10–11
  6. Bergamot, Wild (Monarda fistulosa) — zones 3–9
  7. Black-eyed Susan (Rudbeckia spp.) — zones 3–9
  8. Blanket Flower (Gaillardia spp.) — annual or zones 3–10
  9. Blazing Star (Liatris spp.) — zones 3–8
  10. Bluebeard (Caryopteris spp.) — zones 5–9
  11. Boltonia (Boltonia spp.) zones 3–8
  12. Boneset (Eupatorium spp.) — zones 3–9
  13. Bottlebrush (Callistemon spp.) — zones 9–11
  14. Butterfly Bush (Buddleia spp.) — zones 6–9
  15. Buttonbush (Cephalanthus occidentalis) — zones 4–10
  16. Catmint (Nepeta spp.) — zones 3–9
  17. Celosia (Celosia spp.)  – annual or zones 10–11
  18. Chives, Garlic (Allium tuberosum) — zones 3–8
  19. Cockscomb (Celosia argentea cristata) — annual or zones 10–11
  20. Coneflower (Echinacea spp.) — zones 3–9
  21. Coreopsis (Coreopsis spp.) — zones 3–9
  22. Cosmos (Cosmos spp,) — annual
  23. Crownbeard (Verbesina spp.)  – zones 4–8
  24. Culver’s Root (Veronicastrum spp.) — zones 3–9
  25. Dahlia (Dahlia × hortensis) — annual  
  26. Dewdrops, Golden (Duranta spp.) — zones 9–11
  27. Echinacea (Echinacea spp.) — zones 3–9
  28. Flame Vine (Pseudogynoxys chenopodioides, syn. Senecio confusus) — annual or zones 10–11
  29. Gaillardia (Gaillardia spp.) — annual or zones 3–10
  30. Giant hyssop (Agastache spp.) — zones 2–10, according to species
  31. Globeflower (Gomphrena spp.) —annual
  32. Goldenrod (Solidago spp.) — zones 3–9
  33. Heliotrope (Heliotropium arborescens) – annual or zones 9-11
  34. Hempvine, Climbing (Mikania scandens) — zones 6–9
  35. Ironweed (Vernonia spp.)  – zones 4–9
  36. Joe-Pye Weed (Eutrochium, formerly Eupatorium spp.) — zones 3–9
  37. Lantana (Lantana spp.) — annual or zones 9–11
  38. Marigold (Tagetes spp.) — annual
  39. Milkweed (Asclepias spp.) — zones 3–10
  40. Mint, Moutain (Pycnanthemum spp.) — zones 4–8
  41. Mistflower (Conoclinium spp.) — zones 5–10
  42. Phlox, Garden (Phlox paniculata) — zones 3–8
  43. Porterweed (Stachytarpheta spp.) — annual or zones 9–11
  44. Rose (Rosa spp., varieties with single flowers) — zones 3–10
  45. Rosinweed (Silphium spp.) — zones 4–8
  46. Rudbeckia (Rudbeckia spp.)  — zones 3–9
  47. Sage (Salvia spp.) — annual or zones 5–11
  48. Sage, Russian (Perovskia spp.) — zones 4b-9
  49. Sedum (Sedum spp. et Hylotelephium spp.) — zones 3–9
  50. Spirea, Blue (Caryopteris spp.) — zones 5–9
  51. Spirea (Spiraea spp.) — zones 3–8
  52. Star Flower, Egyptian (Pentas lanceolata) — annual or zones 9–11
  53. Sunflower (Helianthus annua) — annual
  54. Sunflower, Mexican (Tithonia rotundifolia) — annual
  55. Thoroughwort (Eupatorium spp.) — zones 3–9
  56. Tickseed (Coreopsis spp.) — zones 3–9
  57. Verbena, Garden (Verbena x hybrida) — annual or zones 9–10
  58. Verbena, Rose (Glandularia canadensis) — annual or zones 6–9
  59. Verbena, Tall (Verbena bonariensis) — annual or zones 7–9
  60. Yarrow (Achillea spp.) – zones 3-9, according to species
  61. Zinnia (Zinnia spp.) — annual

Do your bit to save monarch butterflies: plant a flower garden!20180328A LyWashu, WC

Coming to Grips with Ragweed

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Deeply cut leaves, reddish stems, narrow green flower spikes? Yep, that’s ragweed (Ambrosia artemisiifolia)!

If you sneeze more often than normal between the beginning of August and the end of September, if your eyes sting, if you’re short of breath and your energy level is close to zero, you are probably suffering from an allergy to ragweed pollen. Hay fever you may call it, although doctors prefer the term seasonal rhinitis. And you’re not alone: in North America, about 10% of the population suffers from hay fever. And ragweed is by far the most allergenic plant on that continent, accounting for almost half of all seasonal allergies.

There are many species of ragweed, always in the genus Ambrosia (Greek for “food of the gods”, a name that was given long before it was understood it caused hay fever!), but it’s mostly common ragweed, also called short ragweed (A. artemisiifolia) that’s the culprit. After all, it’s by far the most common species.

Common ragweed is an annual native to central Canada and the United States, but it spread throughout North America when native forests were cut and replaced with fields of crops, creating an environment similar to the prairies, the plant’s original home. It’s found almost everywhere except in the far north, although populations are moderate on the West Coast and in Atlantic Canada.

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Distribution of ragweed in Europe in 2012. Photo: European Aeroallergen Network

There are no native ragweeds in Europe, but common ragweed has naturalized there as well, probably brought over in contaminated forage seed. It’s been around since the 19th century and is now spreading rapidly and causing serious symptoms in many areas. It’s believed that it will have spread to essentially the entire European continent except the extreme north within the next 35 years.

Small But Harmful

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Common ragweed: the leaves look a lot like those of wild carrot, but are a yellowish green. Photo: Harry Rose, Wikimedia Commons

Common ragweed is a rather insignificant plant from 4 to 38 inches (10 to 70 cm) in height. Its pinnate foliage is deeply cut, much like that of wild carrot or Queen Anne’s lace (Daucus carota), but is yellowish green in color rather than dark green of the latter. Also, it’s usually covered in fine hairs, especially underneath the leaf. Its cylindrical stems are reddish or brownish green, also usually covered in fine hairs. Its flower spike, found at the top of the plant, resembles a very narrow green pagoda … but you won’t see it until the end of summer. The tiny flowers are green or yellowish green too and are not very showy.

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Common ragweed flowers are easily recognizable, but not very striking. Photo: Meneerke bloem,

Ragweed flowers don’t need to have flamboyant colors, as they don’t have to attract insect lr bird pollinators. They are pollinated by the wind. So clouds of ragweed pollen fill the air – and human nostrils – at the end of summer. Each plant can produce up to one billion pollen grains per year, pollen that can travel up to 400 miles (640 km).

The Blame Game

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No, goldenrod doesn’t cause hay fever in spite of beliefs to the contrary. Photo: Olivier Pichard, Wikimedia Commons

For a long time, North Americans blamed goldenrod (Solidago canadensis) for late-summer hay fever. I know my father did: any goldenrod that sprouted on our lot was rapidly put to death! This plant, with bright golden yellow flowers, blooms at the same time as does ragweed and, since the first late summer hay fever symptoms corresponded with goldenrod coming into it’s very visible bloom, it was believed to be the cause of the disease.

Sadly, many people still destroy goldenrod on the pretext that it causes allergies, but in fact it is essentially non-allergenic: its pollen is too heavy to be transported by the wind. Blame instead its inconspicuous cousin, ragweed (both belong to the same plant family, the Asteraceae), whose light-weight pollen is easily carried on the slightest breeze.

Where Does Ragweed Hang Out?

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Ragweed likes bare or nearly bare soil and tolerates poor soils where few other plants will grow. Photo: R.A. Nonenmacher, Wikimedia Commons

Common ragweed is an annual. It has to start from scratch each spring, sprouting from fallen seeds. Unfortunately, its seeds can remain viable for 40 years or even longer. But to germinate, they need sun. As a result, ragweed won’t tolerate competition from taller plants that are already well-established. It instead settles in spots where the vegetation is either low, sparse or absent, thus allowing the sun to reach the ground.

In addition, ragweed is very tolerant of saline soils. In many yards, the place to look for it is along sidewalks, roads and driveways, where grass lawns grow poorly due to applications of road salt over the winter. They kill the lawn or impede its growth, allowing salt-tolerant ragweed to proliferate. You’ll also find it on vacant lots (landfill is not conducive to dense growth of other plants, but ragweed does fine there) and along roads and railways, in parking lots, etc.

You won’t often find it in flower beds or in wooded areas, because the dense vegetation there keeps ragweed from germinating. The use of mulch will eliminate it completely: it simply can’t germinate in a mulched bed.

How to Control Ragweed

If you want to control ragweed, it’s best to start early, in late spring or early summer. Don’t wait until it starts to bloom in late summer.

You could always treat it with herbicides … except that ragweed has become resistant to many common herbicides, such as glyphosate (RoundUp). And obviously, if you garden organically, you won’t want to use herbicides at all. Fortunately, there are other methods.

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Simply mowing ragweed regularly will keep it from producing pollen-bearing flowers.

Since for many homeowners, ragweed is linked to weak or dying lawns near roadways, the best temporary solution is to mow the area frequently. No, this will not kill ragweed plants already present (they’ll sprout again from the base), but at least it will prevent them from flowering. Since common ragweed is an annual, that means it will die with the first hard frosts. Unfortunately, others will sprout in the spring. That’s why mowing can only really a be temporary solution.

For more permanent control, replace weak sod near roadways with either fresh, healthy sod or replace the contaminated soil found there with fresh soil and oversow with quality grass seed. Also, get in the habit, at snow melt, of leaching the soil near the road, letting clear water run for a few minutes to dissolve and carry away salt deposits. That will allow the lawn to grow more densely. And when grass grows densely, ragweed won’t be able to germinate.

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Learn to recognize ragweed when it germinates, as above, and you’ll really be ahead of the game! Photo: weedinfo.ca

If ragweed appears elsewhere on your lot, the easiest action is to pull it out. It doesn’t have a highly-developed root system and is usually easy to yank out. Wear gloves if possible: touching ragweed will not normally provoke dermatitis as long as it’s an occasional thing, but people who regularly handle it can develop contact dermatitis. Yes, another form of allergic reaction!

After you’ve got it out, cover the soil with at least 2 inches (5 cm) of mulch to prevent the seeds from germinating next year or by planting dense vegetation: ground covers for example.

Can You Compost Ragweed?

If the ragweed you pulled out isn’t in bloom, you can add it to your compost bin. But if it is carrying its narrow green flower spikes, be forewarned that the flowers will often mature and even produce viable seed even as the mother plant is dying. Therefore, it’s better to put flowering ragweed plants in the garbage rather than in the compost.


Ragweed should have no place in our gardens.. Make it your duty as a citizen to eradicate it from your own lot… and encourage your neighbors to do so as well!