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Asclepias (fascicularis)

John W. Hunt
Project Manager/Ecologist
University of California - Chico
California State University, Chico
Chico, California 95929-0555
530-898-4363 (fax)

Family Scientific Name: Asclepiadaceae
Family Common Name: Milkweed
Scientific Name: Asclepias fascicularis
Common Name: Narrow-leaved milkweed; Mexican whorled milkweed;
Species Code: ASFA
Ecotype: Seed collected at The Nature Conservancy's Dye Creek Preserve, eastern Tehama County, California
General Distribution: Washington, Oregon, California, Nevada, Utah and Baja California. Dry barren areas from 300-1900 meters (Hickman 1993).
Propagation Goal: plants
Propagation Method: seed
ProductType: Container (plug)
Stock Type: Potted nursery stock
Time To Grow: 0
Target Specifications: First year seedling with fibrous taproot 1-3mm in diameter and 10-30cm long.
Propagule Collection: Collect seed/fruits immediately prior to or when fruit is completely ripe and dry on plant from mid-spring to mid summer
Propagule Processing: Seed was collected from late-summer to early fall; Approximately 30-50 seeds per gram, depending on individual, population, year and cleanliness of seed. Seed was separated from pods and woolly-down by placing large amounts of fruits in pillow-cases and beating vigorously until separated seed collected in the bottom.
Pre-Planting Treatments: None, though clean dry seed was placed in dry, cold storage following collection and prior to sowing.
Growing Area Preparation/
Annual Practices for Perennial Crops:
During November 2004, seed was directly sown into 1.5" deep flats containing a potting mixture of approximately 1:1:1:2 sand:pumice:peat moss:fir bark mixture. Flats were placed in an outdoor cold frame from late-fall though spring. Most seedlings were transplanted into various sized pots ranging form D-pots to 3x4" plastic containers (some seedlings were not transplanted) using the same potting mixture. Because this species forms a taproot the first year, deep pots seem to work best. The active growth phase can be extended by keeping soil moist after the last spring rains. Some authorities recommend well-drained soils. Active growth occurrs well into summer. Dormancy can be induced by letting pots dry-down. Place dormant plants in dry storage until the following fall rains. Better growth may be obtainined during the first year by avoiding transplanting (seed directly into larger containers rather than flats). Based on results of direct seeding in the field, better above and below gound growth may be obtained by planting in native soil (e.g.loam) rather than potting soil. Loam appears to have lower fluctuations in moisture and temperature that stress seedlings and reduce growth during the first year. Growth from seed to dormant seedling follows the first fall rains through the spring-summer dry-down.
Establishment Phase: Initial germination for seed sown in outdoor cold frames was observed within 6-weeks and establishment of rooted sprouts took at least 7-8 weeks. Robust seedlings with fibrous root systems 10-20cm long and < 1 mm in diameter were established by most individuals by the first summer.
Length of Establishment Phase: Transplantablesprouts were established within approximately 7 weeks.
Active Growth Phase: Active growth was observed following the onset of autumn rains (seed swelling) until late-summer/early fall. The active growth phase can be extended well into summer by keeping soil moist. This species appears to grow well in moist, well-drained soil well into summer with little problem.
Length of Active Growth Phase: 6-8 months (later winter to mid summer; older plants may not initiate above-ground growth until spring).
Hardening Phase: Hardening is not necessary as the active growth is generally initiated between mid-late fall and continues until early fall, at which time senescenc occurs. Growth resumes following fall rains and possibly not until late winter/early spring (for older plants).
Harvesting, Storage and Shipping: If soil is kept moist, individuals can be grown through the summer. Senescent plants were placed in dry storage at 60-70 degrees Farenheit.
Length of Storage: 2 months
Other Comments: Flowering: Early May-August; Seed collection: August-September (Oswald and Ahart 2002); Approximately 40 seeds per gram; Transplanted seedlings showed some sign of stress and seedlings transplanted earlier into larger (> 1/2 gallon) containers showed more vigorous growth subsequent to transplanting. Seed sown directly in the field showed above and below ground growth rates comparable too, or better than seed grown under controlled conditions in well-drained potting soils. Heavier native soils may provide better growing conditions when kept moist compared to well-drained potting soils whose moisture and temperature may fluctuate more readily, though many authors recommend well-drained soils for species in this genus.
References: Hickman, James, Ed. 1993. The Jepson Manual: Higher Plants of California. University of California Press, Berkeley, California.; Oswald, Vern and Lowell Ahart. 2002. SelectedPlants of Northern California and Adjacent Nevada. CNPS


Leigh, Mark; Pushnik, James C.; Boul, Rachelle D.; Brown, Matthew R.; Hunt, John W.; Koenig, David A.. 2006. Propagation protocol for production of Container (plug) Asclepias fascicularis plants Potted nursery stock; University of California - Chico Chico, California. In: Native Plant Network. URL: http://NativePlantNetwork.org (accessed 2021/05/11). US Department of Agriculture, Forest Service, National Center for Reforestation, Nurseries, and Genetic Resources.

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