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Asclepias (speciosa)

Lee Riley
Horticulturist
USDA FS - Dorena Genetic Resource Center
34963 Shoreview Road
Cottage Grove, Oregon 97424
541-915-7324
541-767-5709 (fax)
leriley@fs.fed.us

Family Scientific Name: Asclepiadaceae
Family Common Name: Milkweed
Scientific Name: Asclepias speciosa
Common Name: Showy milkweed
Species Code: ASSP
Ecotype: Mt Hood, Rogue River-Siskiyou, Deschutes National Forests, Oregon
General Distribution: The plant occurs in California to British Colombia and Central Canada south to Texas
Propagation Goal: Plants
Propagation Method: Seed
ProductType: Container (plug)
Stock Type: 262 ml (16 in3) container
Time To Grow: 16 weeks
Target Specifications: Stock Type: Container seedling Root System: Firm plug in container.
Propagule Collection: Best to collect when seed pods are brown and about to split
Pre-Planting Treatments: Seeds are placed in fine mesh bags into a 1% hydrogen peroxide (3:1 water/3% hydrogen peroxide) soak for 24 hours, rinsed, and placed in water for an additional 24 hours. The bags are placed in sealed containers in refrigeration at 1 to 3 °C for 45 days.
It is very important to check seeds weekly. If mold is evident, seeds should be treated with 1% hydrogen peroxide.
Growing Area Preparation/
Annual Practices for Perennial Crops:
Greenhouse growing facility.
Seeds are directly sown into containers. Seeds are lightly covered with nursery grit.
Growing medium used is 40:20:20:20 peat:composted fir bark:perlite:pumice with Nutricote controlled release fertilizer (18N:6P2O5:8K2O with minors; 180-d release rate at 21C) at the rate of 1.5 gram Nutricote per 262 ml container.
Establishment Phase: Germination is fairly uniform and is usually complete in 10 to 14 days. Following germination, plants are fertilized with soluble 12-2-14-6Ca-3Mg at 75 ppm for 1 week.
Length of Establishment Phase: 2 to 3 weeks
Active Growth Phase: Seedlings grow rapidly throughout the active growth phase. During the growing season, fertilization depends on weather. Soluble fertilizer (20-9-20 NPK, 20-18-18 NPK, or 17-5-24 NPK) at a rate of 100 to 150 ppm is applied weekly throughout the growing season.
Length of Active Growth Phase: 14 weeks
Hardening Phase: No dry-down is done to induce dormancy. Seedlings are moved to an outdoor growing area in early to mid September.
Length of Hardening Phase: 2 to 3 weeks
Harvesting, Storage and Shipping: Harvest Date: Mid October
Storage Conditions: Seedlings are usually outplanted in fall. No storage except in outdoor growing area. Plants are well irrigated prior to shipping and shipped in containers.
Other Comments: Wetland classification: FAC
It is a good species for stabilization and restoration of disturbed areas due to its extensive root system, drought tolerance, and minimal nutrient requirements.
Irrigation should be closely controlled. Depending on seed source, overwatering may damage plants.
Length of storage for seed viability has not been determined.
References: Dorena Genetic Resource Center Propagation Records, unpublished.

Stevens M. 2000. Plant guide for showy milkweed (Asclepias speciosa). Corvallis (OR): USDA Natural Resources Conservation Service, Plant Materials Center. URL: https://plants.usda.gov/plantguide/pdf/pg_assp.pdf (accessed 9 Oct 2018).

USDA Natural Resources Conservation Service. Asclepias speciosa Torr. showy milkweed. URL: https://plants.usda.gov/core/profile?symbol=ASSP (accessed 9 Oct 2018).

Young-Mathews A, Eldredge E. 2012. Plant fact sheet for showy milkweed (Asclepias speciosa). Corvallis (OR): USDA Natural Resources Conservation Service, Plant Materials Center. URL: https://plants.usda.gov/factsheet/pdf/fs_assp.pdf (accessed 9 Oct 2018).

Citation:

Riley, Lee E.; Klocke, Allison. 2018. Propagation protocol for production of Container (plug) Asclepias speciosa Plants 262 ml (16 in3) container; USDA FS - Dorena Genetic Resource Center Cottage Grove, Oregon. In: Native Plant Network. URL: https://NativePlantNetwork.org (accessed 2024/03/29). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.