Species: Euphorbia esula

Reproduction/Sexual: Flowers of leafy spurge are insect pollinated. The flowers produce copious amounts of pollen and nectar. A survey in Saskatchewan showed 8 orders, 39 families, and 60 species of insects on the flowers of leafy spurge (Best et al. 1980). <br><br>Fruits ripen and seeds are dispersed from mid- to late-July in the United States. The number of seeds produced per stalk varies from 252 seeds in habitats where spurge competes with native grasses to ca. 200 seeds where spurge competes with annual weeds and crested wheatgrass (Selleck et al. 1962). Seed yield can be very high. In Saskatchewan, leafy spurge patches were calculated to produce 24 to 3400 lbs of seed per acre (Selleck et al. 1962). <br><br>Seeds of leafy spurge have a rather high germination rate of 60-80% (Bakke 1936, Bowes and Thomas 1978, Hanson and Rudd 1933). Seed may remain dormant for ca. 5 to 8 years following maturity, but 99% of the germination occurs within the first two years (Selleck 1958). The optimal temperature for germination is 30-32 C. Alternate freezing and thawing, wet and dry periods, and prolonged dark periods promote germination; scarification does not (Selleck 1958). The peak period for germination is late May to early June, but given adequate moisture seeds will germinate throughout the growing season. <br><br>Seed dispersal is initially affected by explosive dehiscence of the seed capsule. The seed may be ejected up to 4.6 m from the parent and distributed fairly uniformly from 0.3 to 4.0 m from the plant (Hanson and Rudd 1933). The seeds can also float and initial infestations often occur along stream or river banks where seeds have floated into appropriate habitat (Biesboer, personal observation). Birds have been implicated in spreading seed but documentation is limited except for sharptail grouse (Noble 1980). <br><br>Reproduction/Asexual: One of the most important aspects of leafy spurge biology (in addition to production of large amounts of seed) is its ability to reproduce and spread rapidly via vegetative reproduction. Vegetative reproduction occurs from both crown buds and root buds that overwinter and produce new shoots in the spring. The crown of leafy spurge develops just under the surface of the soil and produces a large number of buds that annually produce new stems. The crown region of the plant can also produce new roots that contribute to the spread and persistence of the plant. Leafy spurge crowns can live for many years but the number of years is unknown (Bowes and Thomas 1978). <br><br>Seedlings have a remarkable capacity for vegetative reproduction, and can develop buds within 7-10 days after emergence. Buds will form on the proximal portion of the hypocotyl of the seedling. The number of buds produced on the hypocotyl is limited, unlike the roots where up to six times as many buds will form. Bud formation will limit the growth of the seedling. All hypocotylar buds and root buds have the potential to produce a new shoot axis. <br><br>Once control practices have been initiated, it is the root system that ensures that leafy spurge spreads and persists in the soil. The root system, consisting of long roots and short roots, can give rise to shoot buds almost anywhere along its length. The long shoots give rise to most of the buds and have been excavated to a depth of 4.8 m (Best et al. 1980). The upper portion of the plant can be killed by herbicides or tillage but living roots below the treatment zone or detached roots will regenerate new shoots. Cultivation or other shallow removal of leafy spurge plants can actually cause a net increase in the number of stems in an infestation. This was demonstrated by Selleck et al., (1962) who showed that regrowth of leafy spurge after rototilling averaged 316 shoots/sq m in comparison to 134 shoots/sq m in undisturbed control. Shoots can emerge from 90 cm of overlying soil for 5 successive years after removal of the major portion of the root system by excavation (Coupland et al. 1955).