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Narrow Leaf Milkweed
Asclepias fascicularis
About Narrow Leaf Milkweed (Asclepias fascicularis) Nurseries Show All Photos Narrowleaf milkweed or Mexican whorled milkweed is a flowering perennial sending up many thin, erect stems and bearing distinctive long pointed leaves which are very narrow and often whorled about the stem, giving the plant its common names. It blooms in clusters of lavender or lavender-tinted white flowers which have five reflexed lobes that extend down away from the blossom. The fruits are smooth milkweed pods which split open to spill seeds along with plentiful silky hairs. This plant is common in the western United States and has the potential to become weedy.

Milkweeds in general are the larval host plants for Monarch butterflies, and this species is probably the single most important host plant for Monarch butterflies in California. Milkweed gardeners should be prepared for the plant to be eaten by Monarch caterpillars, but will be rewarded by the presence of beautiful Monarch Butterflies. The plant is deciduous in winter and will sometimes die back to the ground before reviving in the Spring, and is often covered with aphids, so often best to plant in less prominent spots in a garden.

It's very easy to grow in soils with with good drainage, even with no summer water.
Plant Description
Plant Type
Perennial herb

Max. Height
1.7 - 3.3 ft (0.5 - 1 m)

Max. Width
1 ft (0.3 m)

Winter Deciduous

Flower Color
White, Lavender

Flowering Season
Summer, Fall

Native Status

Natural Setting
Site Type
Found in many settings including valleys, foothills, canyons, mountains, often dry areas, occasionally in wetlands


Elevation ?
-180' - 11144'

Annual Precip. ?
3.8" - 117.4"

Summer Precip. ?
0.13" - 3.60"

Coldest Month ?
23.0° F - 59.2° F

Hottest Month ?
42.6° F - 87.9° F

Humidity ?
0.47 vpd - 40.28 vpd

Soil Description
Tolerates a variety of soils including sandy, clay and saline

Soil PH
6.0 - 8.0

Soil Toxicity Tolerance
Tolerates Saline Soil

Fast, Medium, Slow

Cold Tolerance(° F)
Tolerates cold to 5° F

Sunset Zones ?
3*, 7*, 8*, 9*, 10, 14*, 15*, 16, 17, 18*, 19, 20, 21, 22, 23, 24

Companion Plants
Works well with a wide variety of other plants, but is best used where its winter leaf loss and summer consumption by caterpillars will not be the center of attention. Also, plant a number of Milkweeds in proximity so that caterpillars will have a sufficient amount to eat. Use with showy, nectar-rich plants that will attract adult Monarchs, such as Indian Mallow (Abutilon palmeri), Ceanothus sp., Western Thistle (Cersium occidentale), California Aster (Corethrogyne filaginifolia), California Fuchsia (Epilobium canum), Buckwheat (Eriogonum sp.), Mint (Monardella sp.), Monkeyflower (Mimulus sp.), Penstemon sp., Sages (Salvia sp.), Apricot Mallow (Sphaeralcea ambigua)

Wildlife Attracted
Butterflies, primarily Monarchs

Landscaping Information
Ease of Care
Moderately Easy

Water Requirement ?
Low, Moderate - High
Extremely Low
Very Low
Moderate - High

Moderately Popular

Max. Summer Water ?
1x/month, 2x/month
No Summer Water
Keep moist

Organic with Rocks

Pest Control
It is crucial to not use any pesticide on this plant or in its vicinity because doing so will be fatal to Monarch caterpillars.

Propagation ?
For propagating by seed: No treatment. Seeds need light to germinate so just gently press them into the soil on their sides without burying them. Keep soil moist. Some seeds germinate in as little as 2 weeks after planting, but others in the same bed may continue to germinate for 1-2 months after that.

Common uses
Butterfly Gardens, Deer Resistant, Bird Gardens

Nursery Availability
Commonly Available

Other Names
Common Names
Mexican Whorled Milkweed, Narrow-leaf Milkweed, Narrow-leaved Milkweed, Narrowleaf Milkweed

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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