cypress spurge

Cypress spurge is an exotic, weedy, herbaceous plant. It is native to Europe and western Asia. It was introduced into the United States in the 1860s as an ornamental ground cover plant. It readily escapes cultivation, and it is now naturalized in North America. Once established, it is difficult to eradicate. It now occurs throughout the United States and southern Canada. It is especially common in the northeast and upper Midwest. In the west, it occurs mostly around major metropolitan areas.

Cypress spurge is an erect, perennial forb that rises from stout, fleshy roots and creeping, horizontal, underground stems (rhizomes). It can be 8″ to 32″ tall, but in Minnesota it is rarely more than 16″ in height. It often forms colonies.

The stems are erect or ascending, densely leafy, round, light green, and hairless. It is usually unbranched below the inflorescence at first, but produces several densely-leafy side branches above the middle after flowering time. The stem and leaves exude a sticky white latex when broken.

Stem leaves are alternate, crowded, and stalkless. The leaf blades are linear, ⅜″ to 13 ⁄16″ long, and 1 ⁄32″ to ⅛″ wide. They are rounded at the base, short-tapered or angled to a sharp point at the tip, and have a single prominent midvein. The upper and lower surfaces are hairless and green, yellowish-green, or bluish-green. The margins are untoothed. At the top of the stem, just below the inflorescence there is a whorl of 10 or more leaves that are similar to stem leaves.

What appear to be flowers are actually false flowers (cyathia) common to the Euphorbiaceae (spurge) family. The inflorescence is an umbrella-shaped arrangement (umbel) of 10 to 18 cyathia at the end of the stem. The umbel has 10 or more primary, hairless, pale green branches (rays). At the tip of each ray there is a pair of inflorescence leaves. These leaves are broadly egg-shaped to heart-shaped or kidney-shaped, about ½″ in diameter, rounded or heart-shaped at the base, and broadly angled to short point at the tip. They are greenish-yellow or yellowish-green, becoming somewhat reddish-tinged as they mature. The rays are usually branched above the inflorescence leaves. Each ray or ray branch ends in a singe cyathium.

Each cyathium is closely subtended by a pair of showy, bract-like structures (cyathophylls). The cyathophylls are about ¼″ in diameter and otherwise similar to the inflorescence leaves. They are greenish-yellow and cupped around the cyathium at first, turning reddish and flattening out as they mature. They appear superficially like petals.

The cyathium is about ⅛″ in diameter on a stalk up to ¾″ long. It consists of an involucre, 4 glands, a single female (pistillate) flower and 15 to 25 male (staminate) flowers. There are no petals or sepals. The involucre is formed from 2 fused bracts and is deeply cup-shaped. The glands are greenish-yellow to yellow, spreading, and crescent-shaped, with a short, outward-curved, hornlike tip at each end. The female flower has 3 styles that are fused at the base for about ⅓ of their length, then split at the tip for about ⅓ of their length into 2 club-shaped lobes. The stamens are crowded around the base of the pistil.

Only a few cyathia produce fruit. The fruit is formed from a compound, 3-chambered ovary. It looks like a capsule but is actually schizocarp. It is 3-lobed, 1 ⁄16″ to ⅛″ long, and hairless, and has a pebbled or warty surface. Each schizocarp contains 1 to 3 grayish, 1 ⁄16″ to 3 ⁄16″long seeds.

8″ to 16″

Greenish-yellow

Leafy spurge (Euphorbia virgata) is similar but a much larger plant, up to 28″ in height. The leaves are larger, up to 4″ long and up to ⅜″ wide, and are not crowded.

Moderately moist to dry. Open woodlands and disturbed areas, including pastures, vacant lots, roadsides, railroads, and graveyards. Full sun to light shade. Sandy or loamy soil.

May to August

The latex exuded by broken stems and leaves of cypress spurge causes a rash in some people similar to that of poison ivy. The plant may also be toxic to cattle and horses.

Sources

2, 3, 4, 5, 7, 22, 24, 28, 29, 30.

Native to Europe and western Asia. Cultivated as an ornamental, escaped cultivation, naturalized in North America.

Plant

Inflorescence

Cypress Spurge
PA WRCP

Cypress Spurge (Euphorbia Cyparissias) - 2012-05-30
Westdelta

Laptele cucului -Euphorbia cyparissias
Adrian Manolache

Euphorbia cyparissias - Zypressen-Wolfsmilch, Cypress Spurge
Frau-Doktor

Amanda
7/10/2024

Location: Roseau County