Most gardeners don’t realize how many beautiful milkweeds (Asclepias spp.) there are for the garden. Here are our favorites for feed monarchs beautifully.
“Monarch butterflies rely on milkweed (Asclepias spp.) flowers and foliage to complete their life cycle. Eggs are laid on milkweed foliage, a host plant for the emerging caterpillars. Chemicals in the milkweed foliage offer protection to the caterpillars, and mature monarch butterflies, making them taste toxic and terrible to would-be predators. Adult monarchs also feed on the nectar-rich flowers of these unique and beautiful plants.” -Mike Darcy
“I have some milkweed seeds and wonder when I should plant them. Should I plant now or wait until spring?” Question from Lynda of West Warwick, Rhode Island
Answer: Start milkweed (Asclepias spp.) seeds indoors in mid to late winter. The seeds of these long-lived perennials can be a little tricky to start because they require a chilling period before they will sprout. (Keep in mind that this only applies to temperate species. Tropical milkweeds, like Asclepias curassavica, don’t need stratification at all.) Here is a materials list and timeline of the steps needed to get these seeds to germinate.
Mid-Winter: Soak your seeds for half a day in lukewarm water. Sprinkle several seeds over small (4″) pots filled with moistened Black Gold Seedling Mix, and lightly cover them with additional mix. (The seeds should be placed about an inch apart. I suggest planting at least a two pots up to ensure you get at least a few seedlings.) Stick labels into each pot with the plant name and date started. Put the pots in large, sealed plastic bags, and then refrigerate them for four to six weeks. Make sure the mix remains lightly moist during this time. (This can also be done in plastic bags of lightly moist potting soil, but I find that the seeds are easier to find and manage if they are pre-potted.)
Early Spring: Remove the pots from the refrigerator, place them in water-holding trays, and lightly water them with lukewarm water. Set them in a warm, south-facing window or beneath grow lights. I prefer to start seeds beneath grow lights. (Click here for an article with an overview of starting seeds beneath grow lights.) Lightly spray the surface soil to keep it moist. The seeds should germinate within two to three weeks. Then water intermittently to keep the pots just moist.
Mid to Late Spring: Transplant the seedlings into their own small pots or into cellpacks, allow them to grow to at least several inches, harden them off, and plant them outdoors.