Cypress spurge, Euphorhia cyparissias L., [EPHCY, euphorbe cyprès, Graveyard spurge, Graveyard weed, Poor man's-hedge, rhubarbe des pauvres] Perennial reproducing by seed and from widely spreading, much-branched underground roots with numerous pink buds and forming dense stands. Stems erect 10 - 80 cm (4 - 32 in.) high, usually much-branched above; leaves alternate (1 per node), very numerous, small, narrow, linear or club-shaped; tip of stem at beginning of inflorescence (flowering branches) with a whorl of 10 or more shorter leaves; flowers yellowish-green on a many-branched umbel (usually 10 or more main branches) at the tip of the main stem and on the upper branches; leaf-like bracts of the inflorescence short and broad, heart-shaped, tapering towards the pointed tip, at first light yellowish-green but usually turning reddish-green to-wards maturity; flowers very small. unisexual, without sepals or petals, and crowded together in a complex structure called a cyathium, like those described for Leafy spurge; one little cyathium between each pair of bracts throughout the inflorescence; each flower cluster producing a 3-lobed seedpod containing 1 to 3 egg-shaped, smooth, greyish seeds l.5-2mm (1/16-1/12 in.) long. The whole plant contains an acrid sticky white juice. Flowering begins in late spring or early summer and may continue intermittently until late autumn.

 Two kinds of Cypress spurge occur in Ontario, a sterile diploid form which does not produce viable seed, and a fertile tetraploid form which produces abundant fertile seed. The sterile form, reproducing only from underground parts was once commonly cultivated in gardens and cemeteries. It has persisted in many localities and occasionally spreads vegetatively to surrounding roadsides and waste places. This form occurs throughout Ontario. The fertile form which can reproduce by seed as well as by underground parts has become a rampant and troublesome weed in Dufferin County and in the Braeside area of eastern Renfrew County, occupying hundreds of hectares of pasture, abandoned cultivated land, woodland, and roadsides.

Although sheep can be forced to eat Cypress spurge and may develop a preference for it, the literature suggests it may be toxic to cattle and horses. The milky juice can be irritating on hare skin and cause a potentially serious rash for some people. It is distinguished from most other plants by its milky juice, its spreading perennial roots with pink buds, its numerous, small slender leaves, and its yellowish-green inflorescence, from the upright annual spurges (Petty, Sun and Broad-leaved) by its perennial habit, and from these and Leafy spurge by its slender stems with numerous, crowded, narrow leaves, its umbel with usually more than 10 slender branches from the tip of the main stem, its heart-shaped bracts or leaves in the inflorescence tapering towards the tip, and by the production of densely leafy branches after early summer flowering.

(Source: Ontario Ministry of Agriculture and Food, Publication 505, Ontario Weeds)