Milkweed 'Swamp'

Butterfly Weed - Swamp (Asclepias incarnata)

A summer-long symphony of mauve and rose, Swamp brings a quiet wild beauty to cultivated gardens. Its sturdy stems lift clusters of soft pink florets that seem to float above the foliage, each one a tiny invitation to butterflies and hummingbirds. The lance-shaped leaves frame the blooms with stately rhythm, creating a vertical grace that feels both natural and composed.

Native to North America, this milkweed is a tender host to monarch caterpillars and a favourite of visiting pollinators. In arrangements, its airy umbels lend form and softness—pair with coral snapdragons for a painterly contrast, or nestle among white cosmos to heighten its romantic, meadowlike tone. A flower that speaks of balance, renewal, and connection to the living landscape.

DETAILS:

QTY: 50

TYPE: Perennial

SITE: Full Sun

DEPTH: 1/4"

GERMINATION: 14 - 21 days at 18 - 21°C

HEIGHT: 34 - 48"

MATURITY: 120 - 130 Days

SPACING: 12 -24"

PINCH: No

HOW TO GROW:

Stratification (Recommended): To mimic natural winter conditions and break dormancy, the seeds require a period of cold.  Moisten seeds in a handful of peat moss or vermiculite, place them in a sealed plastic bag, and refrigerate (cold stratification) at 1-4°C for 30 to 60 days. Alternative: Sow seeds outdoors in late fall/early winter (winter sowing), allowing nature to provide the necessary cold period.

Transplant (Recommended): Sow stratified seeds indoors 7-9 weeks before the last expected frost. Sow 1/4 inch deep into a seed starting mix. This plant develops a taproot upon germination.⁴ Do not allow the seedlings to become pot-bound at any time, as their health will rapidly deteriorate. Transplant seedlings into larger cell packs or 3-4 inch pots just 3-5 weeks after sowing. Harden off the plants and transplant outdoors after the last frost.

Direct Seed: Can be direct sown in the fall (best results, as stratification occurs naturally) or in the spring (using pre-stratified seeds).

Soil, Fertilizing, and Watering: Unlike other Asclepias, Swamp Milkweed thrives in moist to wet soils, making it perfect for rain gardens, borders, or near pond edges. It prefers rich soil but will tolerate average conditions. Fertilizing is usually not necessary. If the soil is very poor, a light application of a slow-release, balanced fertilizer can be used in spring. This plant requires consistent moisture throughout the season and will tolerate temporary standing water. Do not let the soil dry out.

Maintenance and Tips: Cut back the stalks after flowering to a few inches above the ground to encourage a second, smaller bloom. Deadheading before seed pods mature will prevent prolific self-seeding. This is a key host plant for Monarch caterpillars.