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Climbing Milkweed
Fringed Twinevine

Funastrum cynanchoides
(Sarcostemma cynanchoides)

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Watercolor © by Michael Plagens

This watercolor was made based on a specimen found at Cottonwood Wash, Four Peaks, Maricopa Co., AZ, on 12 Sept. 1992. The caterpillar is the immature stage of the Queen Butterfly and the red and black bug is a Milkweed Bug -- Lygeaus kalmii.

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Photo of Sarcostemma hirtellum from southern California © by Michael Plagens

Sarcostemma hirtellum observed at Joshua Tree National Monument where the Colorado Desert, a section of the Sonoran Desert, merges into the Mojave Desert. April 2010. The leaves tend to be narrower and densely short pilose. The petals are greenish as opposed to white.

VINE: Woody vine with thin, wiry stems supported by trees, shrubs, or very often fences. Milky sap that can cause skin irritation rapidly exudes from any broken stem.

FLOWERS: Distinctive, star-shaped flowers are arranged in umbels and are white with tinges of purple.

FRUIT: Turgid, slightly curved pods are packed with comose (hairy) seeds.

LEAVES: Elongate, arrow-shaped to linear leaves are borne in pairs along the stems (opposite) and are not hairy.

RANGE: Frequent along washes and fence rows throughout the Sonoran Desert of Arizona. It is one of the most common vines volunteering on fences in the cities. The wind dispersed seeds can arrive from far away and are lodged agains the fence before germinating. On the fence the escape lawn mowers and power weed-wackers.

Most aphid species are greenish, however, the most common species found on members of the milkweed family are bright orange-yellow. Clusters of 10 to 50 are frequently found on new shoots or on the developing flower buds and fruits. These insects have come to be known as the Oleander Aphid since they are an occasional pest of this exotic ornamental (a member of the related and sometimes included family, Apocynaceae).

Another frequently encountered insect on milkweeds are the brightly colored black and red Milkweed Bugs Whereas the aphids are rather immobile, these true bugs can quickly withdraw their piercing-sucking mouthparts and run or fly if disturbed. If fruits are present, this is where the bugs' feeding will be concentrated.

Queen Oleander Aphid Milkweed Bug

Still another strikingly colored insect, the Queen Butterfly (Danaus gillipus) uses this and other milkweeds as its larval host. That many of these insects are strikingly colored is not a coincidence. Many milkweeds have cardiac poisons in their sap that if ingested by birds or mammals can cause sickness or death. Many milkweed-feeding insects can store these poisons in their bodies without harm to themselves while gaining protection from insectivorous birds and mammals. The colors serve as warning that they are dangerous for insectivores to eat.

Asclepiadaceae -- Milkweed Family

More Information:

Sonoran Desert Field Guide
Sonoran Desert Places
Sonoran Desert Naturalist Home Page

Copyright Michael J. Plagens, page created 23 April 1998, updated 9 June 2012