Rubber, poinsettias, manioc (also known as cassava), and castor oil: all come from the Euphorbiaceae family. Ricinus (castor oil bean) is sometimes cultivated as an ornamental. The only species occurring naturally in the mountaneous Northwest are herbaceous weeds, but most members of the family are shrubs or trees. Species of the family nearly always have alternate, stipulate, simple leaves, although a few have palmately compound leaves. Many produce a milky latex, including all species of Euphorbia. This latex is generally poisonous. All members of the family have separate male and female flowers that grow either on the same plant or on separate plants. Most species have 5 flower segments, but in the genus Euphorbia there is neither corolla nor calyx. The number of stamens varies from 1 to many. There is a single, compound, 3-celled pistil with a superior ovary in which 3 ovules are produced. The style is usually branched. In Euphorbia, what appears as a flower at first glance is, in reality, a part of a flower cluster. The cup-like structure is called a cyathium. In some species, its resemblance to a corolla is enhanced by the presence of flat, often conspicuous glands around the upper edge. These glands secrete nectar. There are 5 individual stamens or 5 clusters of stamens. These are attached to small stalks that are, in turn, attached to the inside of the cyathium. These stamen stalks are one indication that the cyathium is not a perianth. Each fascicle is an individual staminate flower. There is only one pistillate flower in each cyathium. It is a pretty minimal flower, consisting of a single pistil on a short stalk (pedicel). As in all members of the family, the pistil is 3-celled. The seeds often have a swelling that is rich in oils.
Guide to Identify Presented Species of the Spurge Family
UPRIGHT PLANTS, LEAVES NARROW
Euphorbia esula – Leafy Spurge Herb with milky juice, 20-90 cm tall. Weed on disturbed ground.
Flowers greenish-yellow, lacking petals and sepals, in umbrella-shaped clusters.
Leaves alternate, 2-6 cm long, linear, numerous, stalkless.
UPRIGHT PLANTS, LEAVES BROAD
Euphorbia robusta – Rocky Mountain Spurge Herb with milky juice, 10-30 cm tall. Dry areas, foothills and lower mountains.
Flowers greenish-yellow, lacking petals and sepals, in umbrella-shaped clusters.
Leaves alternate to opposite, 1-2 cm long, ovate, pointed, numerous, stalkless.
Alphabetical listing with links to presented species of the Spurge family:
