Leafy spurge, Euphorbia esula complex*, [EPHES, euphorbe ésule, euphorbe feuillue] Perennial, reproducing by seed and by widely spreading underground roots having numerous small pinkish buds from which new leafy shoots are produced. Similar to Cypress spurge but taller and coarser. Stems erect, up to 1 m (40 in.) high; leaves numerous, alternate (1 per node), or crowded and some appearing opposite (2 per node), 3 - 7cm (1¼ - 3 in.) long, linear or wedge-shaped, and 1 whorl of 7 or more leaves at the tip of the stem; inflorescence greenish, flowers tiny, unisexual and very unusual: several male (pollen-producing) flowers consisting only of single, tiny stamens without sepals or petals, and 1 female (seed-producing) flower consisting only a single pistil also without sepals or petals crowded in a cup-like structure, the rim of which has 4 yellowish U-shaped glands and 4 tiny lobes, the whole complex of several tiny male and one female flowers in a cup being called a cyathium; seedpods 3-lobed, containing 3 seeds about 2.5 mm (1/10 in.) long, smooth, greyish to yellowish or brownish and usually with a tiny yellow bump near the base: the seedpods exploding when dry and throwing the seeds several meters in all directions. The plants are deep green to almost bluish-green during spring, changing to yellowish-green or olive-green at flowering time during June and July, and changing back to a dull green or sometimes  reddish-green after flowering; then sometimes with a secondary period of flowering in late August or September. shedding seeds while still flowering.

Leafy spurge occurs in several localities throughout Ontario, occupying a wide variety of soils and habitats, including cultivated land, meadows, pastures, waste places, open woodland, roadsides, and gardens. It is distinguished from most other plants by having milky juice, spreading roots with pink buds, its slender green leaves that are mostly alternate, and its yellowish-green inflorescence, and from Cypress spurge by its taller, coarser habit, longer leaves. and fewer branches in the main umbel at the tip of the stem. It is distinguished from the annual erect spurges by its perennial habit, and tall, coarse sterns with mostly linear leaves. *There is still considerable confusion about the botanical name for the Leafy spurge that grows in North America. What is called Leafy spurge is actually a complex of several closely related groups of plants which seem to have physiological differences but are very similar in appearance. Insects and disease organisms can tell the difference even though people cannot! The names virgata and E. pseudo vigata are also being used for this complex in current literature.

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