Not-So-Floppy-Headed Canadian Milkvetch

When you think of legumes, you're more likely to think of string beans and peas than you are ornamentals. Or maybe you're savvy about pasture plants, and how some vetches help enrich the soil while fattening up livestock. But if it's the combination of "Canada" and "beans" that piques your curiosity, and you've been following this blog, you know what's coming next: Something completely juvenile, such as a Terrance and Phillip reference.

We can't help ourselves.

We're not going to link to clips featuring these (Not Safe for Work/Children/Clergy) South Park characters—this is a family gardening blog, after all—but...oh, fine. Here you go. When you're done, come on back; we'd like to tell you about Canadian milkvetch, and how you can try growing vetch from seed in your own garden.

Origins, taxonomy, and cultural history

Oh hey! You haven't run off! Good!

Canadian milkvetch (Astragalus canadensis) is very closely related to the true vetch genus (Vicia) best known for its large-scale use as a cover crop, green fodder, and green manure. Both are members of the pea family (Fabaceae) and can enrich the soil if the seeds are inoculated with rhizobium—bacteria that works with a legume's root system to fix nitrogen in the soil.

Where Vicias tend to resemble tender pea plants more closely, Canadian milkvetch can grow as large as 3.5' tall in the garden and serve as attractive stand-alone ornamentals.

Another critical difference between the Astragalus and most of the Vicia genera? Milkvetch is toxic to livestock, much in the same manner as is larkspur, and it shouldn't be grown near hayfields or pastures. While Canadian milkvetch isn't quite as hazardous as other species and is sometimes used as a short-duration grazing plant, its toxins have a cumulative effect; most ranchers and pasture-based producers steer (ha!) clear of all but a few true vetches, or use field peas instead.

Canadian milkvetch is native to much of North America, favoring the prairie regions of Alberta and the United States. It doesn't overwinter in the coldest regions where winters dip below -25°F but easily reseeds itself, taking advantage of the natural winter frost/thaw stratification process.

In spite of the dangers, Astragalus canadensis has a long history of natural healing among North American aboriginal cultures. According to Practical Plants, the root was boiled to make a broth or tea or chewed and used as a poultice. It treated superficial skin wounds, fevers in children, and chest and back pains. It also helped with pesky coughs and the unpleasant (and socially awkward) experience of spitting up blood.

Some Old World Astragalus species are promoted as immune-boosting, cancer-preventing "superfoods." In a world in which essential oils and natural remedies have become a bazillion-dollar industry, it's a good idea to consult with your physician to make sure you're not doing more harm than good, especially if you're on medication that may interact poorly with alternative remedies.

Canadian milkvetch in the garden

Astragalus canadensis is incredibly versatile, adapting to almost any garden environment. The Ladybird Johnson Wildflower Center describes its native habitat as moist to dry prairies, stream banks, and forests with open canopies.

Though its flowers are usually described as white, they're just as often pale green or yellow. Approximately 75 flowers bloom around and up each of several terminal spikes (racemes), much in the same manner as lupines and snapdragons. (Lupines, by the way, are milkvetch cousins.) Each tube-like, upwardly-curved blossom of five fused petals is approximately 1/3" to 3/4" long, secreting rich nectar for long-tongued pollinators such as hummingbirds and butterflies. Milkvetch is an important food source for the western tail-blue butterfly (Cupido amyntula). When the flowers die back and the seed pods dry, they rattle when shaken...earning the plant the nickname, "rattle weed."

Given the thinness of the plant's stems and flowering spikes, one would expect the racemes to live up to South Park's "floppy-headed Canadian" epithet, but the arrow-shaped flower formations tend to hold their composure pretty well. At least better than we did when the cartoon debuted in 1997.

Canadian milkvetch has 6" long, pinnate, compound, alternating leaves. There are roughly two to three dozen oblong leaflets per leaf stem, and each is approximately 1" long. They're typically a deep, rich green with fine peach fuzz. When planted in groups under ideal conditions, the foliage is dense, forming a lush background beneath the flowering racemes. In drier climates, Canadian milkvetch takes on a more sparse appearance, though the plants retain their prolific blooming tendencies.

• USDA Hardiness Zones: Herbaceous perennial in zones 3 through 8, with exceptions for coldest regions. Annual elsewhere.
• Sunlight Preferences: Full sun, some afternoon shade.
• Moisture Requirements: Prefers intermittent to scarce irrigation but does well with regular watering if the soil drains easily.
• Soil Preferences: Poor to medium quality, well-draining soils. Avoid overly rich beds. Likes sandy soil!
• pH: neutral to alkaline soils between 6.0 to 8.0.
• Plant Height: 1' to 3.5' tall.
• Plant Width: 8" to 24" spread.
• Growth Habit: Upright, shrubby, spreading.
• Bloom Period: May through July; sometimes through the summer with increased irrigation during peak heat.

Given the variance in height, it's difficult to predict whether they'd make tidy, formal border plants, but they do look good on the south side of tree plantings, at the foot of fences, walls, foundations, or as intermediary plants between borders and taller specimens. They're not good container candidates due to their deep taproots, but they will take hold in rock gardens and boulder piles. They do just as well in xeriscapes as they do near downspouts, on swales, or along pond edges.

We think they look best in clusters, especially in dry, neglected garden patches well outside of irrigation zones. Since they're found on our southern border just as often as that between the US and Canada, they're a good choice for desert-themed landscapes.

Pests, diseases, and maintenance

Deadhead the plants in summer and cut them back to clean up your beds in the fall. It's not necessary to mulch them to preserve moisture since they prefer to dry out in between watering, but if you're gardening in an area with particularly hot summers, a light-colored mulch will protect the roots from overheating.

Astragalus canadensis isn't particularly subject to significant issues, though caterpillars—especially the western tail-blue butterfly (Cupido amyntula) larvae—depend on Canadian milkvetch for sustenance. So does a tiny bean weevil classified as Acanthoscelides aureolus, which eats the seeds. Acanthoscelides aureolus doesn't have a common name, by the way, so if you come across one of these bugs, introduce yourself and find out what it is.

Deer like to nibble on Canadian milkvetch, but they instinctively move on to your roses after a few bites.

Harvesting Canadian milkvetch

We're not going to encourage the plant's use as a medicinal or culinary herb, but if you want to use them as cut flowers, knock yourself out! Cut the long stems as close to the base as possible, and immediately put them in water. Don't forget to include the attractive foliage. Be sure to pick up any dropped flowers or leaves to prevent pets and little kids from ingesting them.

Growing Canadian Milkvetch from seed

Canadian milkvetch should be direct-sown either in fall or spring. It has a long, rapidly-growing taproot that's sensitive to disturbance, so it doesn't transplant well. Another of this plant's cranky qualities is its need for cold stratification before planting...a step you can (and should) skip if you plant the seeds in fall.

To prepare your seeds for spring planting, we recommend that you either stash your seed packet in the refrigerator for a few weeks or use the damp paper towel method for 10 days. Another acceptable method is to soak them in near-boiling water. Allow the water to cool to room temperature, and let the milkvetch seeds soak for up to 24 hours. You can also give the seed hulls a couple passes with an Emory board to help break down the outer coating.

Once you've sufficiently tortured the seeds, prepare the beds by removing any debris. Loosen compacted soils down to about 10" inches, and add some sand and well-aged compost to improve drainage.

• When to Plant Outdoors: In spring, immediately after the last frost; in fall, anytime after the first frost, up through early winter.
• When to Plant Indoors: Not recommended.
• Seed Depth: 1/2" to 3/4"
• Seed Spacing: 18" to 24"
• Days to Germination: Seedlings should emerge in spring within 10 to 21 days at 65°F to 70°F.

When growing vetch from seed, be sure to keep the seedbeds consistently moist until the seedlings have emerged and become established. Take care not to disturb the soil around your milkvetch plants during this period.

We're not Canadian, but we're just as friendly!

Seed Needs is headquartered in New Baltimore, Michigan—just across Anchor Bay from our Canadian neighbors. We might not be able to offer up a better version of Tim Horton's donuts, but we can promise you the highest quality Canadian milkvetch seeds. Some folks might think that's not much of a consolation prize, but they haven't seen this stuff in full bloom.