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Asclepias (incarnata)

Jan Schultz
Forest Plant Ecologist
USDA FS - Hiawatha National Forest
1030 Wright Street
Marquette, Michigan 49855
906.228.4484 (fax)

Family Scientific Name: Asclepiadaceae
Family Common Name: Milkweed Family
Scientific Name: Asclepias incarnata L.
Common Name: Swamp Milkweed
Species Code: ASIN
General Distribution: Found in a variety of soil types. Noted for inhabiting wet places, but grows well in fields, roadsides, waste places and dry sites. A single stem up to 3-6 feet in height. Has a pink flower.
Propagation Goal: plants
Propagation Method: seed
ProductType: Container (plug)
Time To Grow: 0
Propagule Collection: Seed is collected by hand from locally native plants in the eastern central Upper Peninsula. Flowers June-August. Fruit is a pod with numerous seeds. Each has a coma. Seed is harvested in October.
Propagule Processing: Seed can be readily removed from ripe pod by cracking the pod and pulling the seed from one side of the pod, leaving the "parachutes" behind. Dry seeds for 1 to 2 weeks in open paper bags or open Rubbermaid-style bins. Once seeds have been dried, seal the seeds in a Rubbermaid-style container or Ziploc-style bag with an equal amount of vermiculite or perlite and add enough water to barely saturate the mixture. Keep in a cool dry place (refrigerator or cold garage) until planted. Cold store until planted (up to 3 years). Seed storage in cold conditions may enhance, but not duplicate, the stratification process. Seeds are not cleaned.
Pre-Planting Treatments: Requires one week of moist cold stratification. No adverse effects for longer stratification period.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Propagation Environment: Greenhouse made of standard U.V. 3HL Clear 6mil from (J.R. Johnson Supply Inc.). Fans run continuously to circulate the air. Vents open during the summer months for cooling. Container Type: swamp milkweed grows best in 14"x8.5" trays having 24 cells, each cell being 2" in diameter and 4" deep. Growing Media: Scotts Redi-earth Plug and Seedling Mix. Contains vermiculite, and sphagnum peat moss. Soil is sterile.
Add enough water to the soil to saturate. Mix soil with a trowel. Cover the holes in the bottom/sides of the plug tray cells with newspaper, as the soil will fall through. Fill cells with damp soil and press soil down with a spoon. Refill the cells plugs with soil to the top, this time not pressing it down. Thoroughly moisten soil in the plug cells, but do not saturate. Sow the seeds by hand at a rate of about 3 seeds in each cell. Cover the seeds with a thin layer of soil or gently press the seeds into the dirt. Sow January thru July.
Establishment Phase: From Jan. thru Aug. the greenhouse thermostat is set at 65 degrees F both day and night. Ambient greenhouse temperatures may reach 100 degrees F during the day in the summer. From Sept. thru Dec. the thermostat is set at 55 degrees F. During this season ambient greenhouse temperatures may reach 75 degrees F during the day. The greenhouse holds plants at all stages of development so the temperature setting stays the same for all plants at all stages of growth. Soil is kept consistently damp during germination. Water using a fine mist or light hose setting only. Newly planted trays are placed on the south side of the greenhouse. No articial light is used.
Active Growth Phase: The soil does not need to be consistently moist. Move trays to cooler north greenhouse tables. No fertilizers are used.
Hardening Phase: In early-late spring, mature plants can be moved into a cold frame with a cover of material that diffuses sunlight to prevent scorching of plants. When the danger of frost has passed, leave plants outside. Water less frequently.
Harvesting, Storage and Shipping: In the Upper Peninsula, flats are out-planted from late May to early October. Flats that are not planted in the summer remain in the greenhouse for another season. Transplant if needed.
Other Comments: Spreads by rhizomes. Dry site tolerant. Beautiful flower. Host plant of monarch butterflies.


Schultz, Jan; Beyer, Patty; Williams, Julie. 2001. Propagation protocol for production of Container (plug) Asclepias incarnata L. plants USDA FS - Hiawatha National Forest Marquette, Michigan. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2020/10/23). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.

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