Swamp Milkweed, Asclepias incarnata
A showy two foot tall perennial with fragrant, terminal blossoms made up of tiny rosy-purple blossoms. This milkweed prefers average to very moist soils, will tolerate heavy clay soils and is easy to start from seed and deer resistant. This hardy perennial, whose scientific name comes from the Greek god of medicine, is a favorite of butterflies, native bees and hummingbirds. The seeds are very easy to grow and do well when planted in the fall or when cold-treated for three months prior to planting. Swamp Milkweed will spread through seed distribution and underground shoots. Monarch Butterflies and Queen Butterflies lay their eggs on the milkweed and the larvae feed on the plants. Note that these plants contain cardiac glycosides, chemicals, that are toxic when eaten and make the Butterflies also toxic to any would-be predators. These will spread easily and may need to be controlled. These are good for wetland rehabilitation and as a component in wildlife seed mixtures. It is widely distributed across the U.S. and Canada from Quebec and Maine south to Florida and Texas and west to Nevada and Idaho. This species prefers neutral to slightly acidic soil, although it will tolerate a pH up to 8.0. It has high moisture requirements, and it is usually found in moist habitats such as wet meadows, riverbanks, pond shores, stream banks, wet woods, swamps, and marshes, although it will also grow in drier areas such as prairies, fields, and roadsides. Swamp milkweed needs full sun or partial shade to flourish.
Germination temperatures between 65 and 75 deg. F. Can start indoors and transplant when plants are 4-8 weeks when all danger of frost is past.
Climate: Sun/part sun-Avg/Moist
Rate: 1oz./60 sq.ft.
Bloom time: June-Sept.
Packet weight: 2 gms (approx. 300 seeds)
Some tips for planting and growing Milkweed successfully
Milkweed seed has a high percentage of dormancy, which means that many of the seeds in your packet won’t germinate without special treatment or will germinate, not this season, but maybe the next season. So here are some suggestions.
Milkweed seeds need to be exposed to cold temperatures that normally occur in winter to help to break the natural dormancy and help to soften the hard outer casing. If you are planning to start your Milkweeds indoors, you will need to do this cold stratification, yourself. You can do this by putting your Milkweed seed in a damp paper towel, folding it to fit into a sealed plastic bag, then placing the bag into the refrigerator. Keep it there for 4-6 weeks.
Other methods: Nick seeds with a sharp razor blade. Soak seeds in hot (190 deg. F, to start) water for 12 hours prior to planting. (not as successful)
Plant in small 2-4″ peat pots (recommended) or tall plastic pots. Use ‘seed-starting’ soil or medium. Moisten the soil, place 1-2 seeds into each pot and cover with no more than 1/6″ damp soil or medium. Place the pots where they can drain. Water gently or fill a tray with 1/2 ” water to be absorbed from the bottom of the peat pots. Dump the excess water after absorption. Water when the top of the soil is dry and don’t overwater. Milkweed seeds germinate in warm conditions, so place tray of pots in a warm sunny window, greenhouse, or under a grow light. Germination in 10-15 days for cold-stratified seeds. To encourage sturdy stems, place your grow light bulb close to the soil. Sometimes a small fan blowing gently towards the new seedlings will encourage sturdier stems.
– Other planting methods:
Plant non-stratified seed into peat pots filled with seed-starting soil or medium. Moisten, and place in a greenhouse or under grow light. This germination might take several months. If planting outside, seed in late fall. Let the Milkweed seed remain over the winter. This will accomplish the cold-stratification, needed. Germination should occur when the soil warms and the days are longer.
When plants reach 2-3″ tall, transplant outdoors in full sun in early spring after danger of frost is past. Milkweed produces a long taproot, so take care to not disturb the roots. Plant peat pots so that the top edge of the small pot is underground to avoid drying out. If your Milkweed seedlings were planted in plastic pots, take extra care to not disturb the roots. Water after planting until plants are established. Then tapering off, unless the season is extremely dry. The newly planted Milkweed seedlings may lose all their leaves due to transplant shock but should grow them back again.