The seeds of asclepias incarnata, as well as asclepias tuberosa, will self-sow in the garden if the pods are left on the plants. In other words, you can let Mother Nature sow more milkweed plants. However, because the milkweeds are late to emerge in the spring, it is easy to disturb or destroy the new plants while working in the garden. Even mature milkweed plant locations need to be marked. Here in my zone 7 garden, the milkweeds emerge in June.
Asclepias incarnata, or swamp milkweed is best sited in moist, even boggy, soil locations.
Any plant that self-sows in your garden is a good candidate for fall sowing. For example, I collected the seeds of echinacea 'Prairie Splendor' and purchased seeds of echinacea 'Ruby Star'. I sowed the seeds in October last year while sowing larkspur, poppies and planting allium bulbs. By late spring, the seedlings were showing in the garden. In the last week, a few of the plants started blooming.
There are some disadvantages to sowing seeds in the fall. If you mulch or add compost to your garden, then the seeds will be covered over with a layer of organic matter, making it difficult to germinate. Areas of bare garden soil are needed for direct sowing. Birds may also forage and pick seeds sown in the garden, especially the seeds of flowers that they love, such as echinacea. Some weed suppressors, such as corn gluten, will not only suppress weed seed germination, but also the good seed germination!
Asclepias incarnata (like other milkweeds) is poisonous, so always handle the plants and seeds with care. The flat seeds barely need to be covered with soil, whether sowing in the garden, winter sowing or starting indoors. Asclepias incarnata seeds require refrigeration if started indoors.
Great directions for starting milkweed seeds are available from Monarch Watch. If you purchase any seeds, the packets should always come with directions for proper sowing.
Since asclepias incarnata seeds need cold stratification, some gardeners refrigerate the sown seeds in the cell packs in a refrigerator. I don't have an extra refrigerator for starting seeds after sown in the soil, so I will fall sow my seeds.
Those who like to winter sow, can start their seeds in containers outside in late winter. Seeds can also be placed between moist paper towels inside a ziplock bag to be refrigerated before sowing out in the spring after danger of frost has passed.
Perennials sown from seeds may take longer, sometimes 2 years, to bloom compared to large size plants that are purchased in pots from a nursery. Sow your seeds, mark the spot and be patient! Pink swamp milkweed is a beautiful perennial that is beneficial to bees and Monarch butterflies.
Photos and words by Freda Cameron