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Snow-on-the-Mountain, Snow-on-the-Prairie (Euphorbia marginata and Euphorbia bicolor)
By Ann Black and Jeff Sparks

Snow-on-the-Mountain and Snow-on-the-Prairie are two closely related plants that are important members of the North American prairie. Although they have some characteristics of milkweeds, including a milky sap and thick fleshy leaves and stems, they are not milkweeds! They actually belong to the Euphorbia or spurge family of plants. All parts of these plants (leaves and stems) when broken or detached exude a thick milky resin or sap composed of latex. (See Toxicity information below).

Ethnobotany: The sap of Snow-on-the-Mountain forms latex that was used for chewing by the Kiowa. Some early cattlemen used the plant's juice for branding cattle in preference to a hot iron (Diggs et al. 1999). There are accounts of native and frontier peoples using the plants as purgatives and cauterizing agents. The plant is often cultivated as a self-seeding ornamental annual, and seeds are available.

Toxicity: All parts are poisonous. Routes of exposure include ingestion, skin and eye contact. Contact with skin causes redness, swelling, and blisters after some delay. Skin should be washed thoroughly with soapy water following contact with the sap. Nausea, vomiting and diarrhea are the symptoms that occur when the sap of plant parts are ingested. Purgatives should not be used as ingestion causes only low toxicity. The toxic compounds are diterpene esters in milky latex. Eye contact can causes mild to severe irritation depending on the amount of exposure. The eyes should be thoroughly irrigated with sterile saline eyewash.

Wildlife Value: Butterflies and other insects are attracted to the nectar of snow on the mountain and prairie. While, most other wildlife and livestock do not eat these plants because of the noxious milky resin. These plants are usually deer and rabbit resistant. However, bucks in velvet will attack larger plants. Sheep and goats can eat a quantity of the plants without ill effects.

Snow-on-the-Mountain: is a prolific, tall, annual wildflower, which grows from 1 to 5 feet tall and has several branching stems at the top of the plant. The local habitat and environmental conditions have much influence on mature height, branching and eventual flowering of the plant. Snow-on-the-Mountain can be found solitary or growing in large colonies. These large colonies are probably what inspired its common name. The seedlings begin as single stems with green solitary leaves. Later on, and very spectacularly, the stems begins to branch. Leaves at the ends of each branch have white striped margins.

In later summer, flowers develop at the ends of each branch. Unless damaged or intentionally pruned, the plants are not branched below the inflorescence. What appear to be white-petaled flowers are actually striped leaves or bracts that lie beneath the true flowers. Each flower is composed of specialized nectar gland appendages that form a cyathium or cup that holds the very small true flowers. According to Marshall Enquist, Wildflowers of the Texas Hill Country, each cyathium contains one female flower and up to 35 male flowers. When fertilized, female flowers form tiny capsules, each containing three seeds. Bloom Time: July to October. Range: These plants can be found from Minnesota to Montana, south to Texas and New Mexico at elevations up to 7,000 feet. In other areas, plants have escaped from cultivation. Photo By: Ann Black

Snow-on-the-Prairie: looks much like E. marginata, but is a smaller plant with narrower leaves. It is found in East Texas, and has a smaller distribution in North America. It achieves a height of 1'-4'. It is not browsed by cattle. Snow-on-the-Prairie blankets the prairies with white in the very hottest, driest part of late summer. Bloom Time: Late summer until frost. Photo: www.biosurvey.ou.edu

Photo By Ann Black

Photo By: Ann Black