Like many gardeners, I envision my garden’s front edge as a tapestry of beautiful flowers. In addition to serving as a colourful entryway to the vegetable garden, flowers attract pollinators and other beneficial insects.
Unfortunately, my front bed stands exactly at deer browsing level, so strong deer (and rabbit) resistance is required of anything I try to grow. I have excellent luck with fragrant herbs, mint relatives, and any kind of poppy, but several of my newest additions are well-behaved milkweeds, which insects love but animals abhor. Milkweeds also are of critical importance as larval host plants for endangered monarch butterflies in the US.
Commonly called butterfly weed, Asclepias tuberosa grows into a low mound less than 3 feet (1 m) wide, is rarely invasive, and produces long, pointed seed pods that are fun to use in dry arrangements. Growing best in warm sun, this species often prospers on hillsides and other tough spots where dry soil is an issue.
Butterfly weed mosty commonly blooms in a rich orange colour, but can also be found in several more strong colours from rich red to pale yellow such as those present in the ‘Gay Butterflies’ seed mixture, and a mixture gives you colour diversity from the start. In the UK, butterfly milkweed seeds are available from Chiltern Seeds and other suppliers.
A second species of garden-worthy milkweed, Asclepias incarnata, is often called swamp milkweed, rose milkweed, or red milkweed. All strains of rose milkweed feature a spicy vanilla fragrance, acceptance of part-day shade, and a long bloom time provided stems are harvested regularly for bouquets. And, although this species adapts to moist conditions, it is perfectly at home in a well-drained garden bed.
‘Soulmate’ is a popular fragrant pink cultivar that can be grown from seed or from a purchased plant. The bloom clusters of ‘Cinderella’ are mauve pink, ‘Ice Ballet’ is creamy white, and ‘Milkmaid’, bred for use as a cut flower, is almost white.
The stems of both these types of milkweed make good cut flowers, with two precautions. First you must check to make sure the stem you want is not hosting monarch eggs or larvae. Once cut, allow some outdoor time for tiny insects to vacate the blossoms before working with the stems indoors.
Wear protective gloves when cutting, pruning or trimming all milkweeds, because the white sap is unpleasantly sticky and causes dermatitis in some people. To help cut milkweed stems last up to a week, sear the cut ends in a candle flame to seal them.
In the US, common or field milkweed (Asclepias syriaca), and its western counterpart, showy milkweed (A. speciosa) are phenomenal plants for monarchs and other butterflies, but both are aggressive spreaders. They are best used in wildflower gardens where neatness does not count, or in a plot adjoining a mowed area.
Should you have an abundance of common milkweed, you might consider cutting back some plants by half their size in early summer before they bloom. They will develop new growth and blossom clusters that will be available for use by late-generation monarchs.
Growing Perennial Milkweeds from Seed
Last spring I worked with a local native plant group growing thousands of perennial native plant seedlings, including three species of milkweed. When the seedlings were ready, we gave them away at pop-up Wildflower Wednesday events in the town’s farmer’s market space.
It was fun and educational. We found that many of the excellent milkweeds discussed above can be grown from seed sown indoors or outdoors in late winter. Winter sowing techniques or cold-stratifying seeds in damp sand may enhance germination, but special treatment is generally not necessary with butterfly milkweed seeds. Once the cold-hardy seedlings are up and growing, they can be moved outdoors with little protection unless the weather turns nasty. Indeed, exposing the seedlings to cold spring weather improves the chances that the plants will bloom nicely in their first year.
With common milkweeds, simply sow the seeds where you want the plants to grow. Very young seedlings that pop up in unwanted places can be moved or potted up, but older plants are not willing transplanters. Do be aware that common milkweeds take off in odd directions starting in their second year. Don’t say I didn’t warn you.