Asclepias fascicularis Decne.
Mexican Whorled Milkweed, Narrowleaf Milkweed
Asclepiadaceae (Milkweed Family)
Synonym(s): Asclepias mexicana
USDA Symbol: asfa
A 1-3 ft. perennial with several erect stems and narrow, whorled leaves. Several 4-5 in. wide flower clusters occur from the upper leaf axils. Individual flowers are greenish-white, often tinged with purple. The subsequent milkweed pod is smooth and slender.
From the Image Gallery
Plant CharacteristicsDuration: Perennial
Root Type: Tap
Leaf Retention: Evergreen
Leaf Complexity: Simple
Leaf Shape: Lanceolate , Linear
Leaf Venation: Pinnate
Leaf Margin: Entire
Leaf Apex: Acute
Breeding System: Flowers Bisexual
Fruit Type: Follicle
Size Notes: Up to about 3 feet tall.
Leaf: Narrow to lanceolate, up to 6 in (15 cm) in length and ¾ in (2 cm) in width.
Flower: Color is pale pink, purple, white, to greenish. Umbels stand erect. Horns protrude through the hoods. After blooming the corolla extends down under the hoods. Corolla color is white to pinkish in contrast to the hoods and horns being white. Several umbels are born on each stem. 20+/- flowers per umbel. Flowers are 3/16 in (4-5 mm). Pedicels are 3/16 – 7/16 in (6-10 mm).
Fruit: Pods narrow, thin, smooth, and long. Form in July and can be picked late July. Length is (6-9 cm). Seed Color is Light Brown, 1/8 – 1/3 in (3-8 mm) long.
Bloom InformationBloom Color: White , Pink , Green , Purple
Bloom Time: Jun , Jul , Aug , Sep
DistributionUSA: CA , ID , NV , OR , UT , WA
Native Distribution: N.e. WA & ID, s. to Baja CA & n. AZ
Native Habitat: Dry climates, plains, hill, valleys, roadsides, and disturbed grounds. Occurs in a variety of dry to moist places below 7000 ft.; uncommon in the desert.
Growing ConditionsWater Use: Low
Light Requirement: Sun
Soil Moisture: Dry , Moist
Drought Tolerance: High
Soil Description: Dry to moist soils. Grows well in clay soils and on moderate slopes.
Conditions Comments: Not shade tolerant, needs full sun. Easy to grow and quite drought tolerant.
BenefitWarning: All plants in the genus Asclepias are probably somewhat toxic, some fatally so, to both humans and animals. The sap of some causes skin irritation in humans. Sensitivity to a toxin varies with a person’s age, weight, physical condition, and individual susceptibility. Children are most vulnerable because of their curiosity and small size. Toxicity can vary in a plant according to season, the plant’s different parts, and its stage of growth; and plants can absorb toxic substances, such as herbicides, pesticides, and pollutants from the water, air, and soil.
Conspicuous Flowers: yes
Value to Beneficial InsectsSpecial Value to Native Bees
Special Value to Bumble Bees
Special Value to Honey Bees
Supports Conservation Biological Control
This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.
PropagationDescription: Sow seed.
Seed Collection: Not Available
Seed Treatment: No treatment.
Commercially Avail: yes
Find Seed or Plants
Find seed sources for this species at the Native Seed Network.
National Wetland Indicator Status
From the National Organizations DirectoryAccording to the species list provided by Affiliate Organizations, this plant is on display at the following locations:
Native Seed Network - Corvallis, OR
Additional resourcesUSDA: Find Asclepias fascicularis in USDA Plants
FNA: Find Asclepias fascicularis in the Flora of North America (if available)
Google: Search Google for Asclepias fascicularis
MetadataRecord Modified: 2022-09-18
Research By: TWC Staff