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Leafy spurge Euphorbia esula L. |
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Keys to Identification:
Flowers are yellowish-green and have a pair of heart shaped yellow-green bracts below each inconspicious flower
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This information courtesy
of the Colorado Natural Areas Program Family: Euphorbiaceae (Spurge) Other Names: none widely accepted USDA Code: EUES Legal Status: Colorado Noxious Weed List B Identification Growth form: Perennial forb Flower: Flowers are yellowish-green, small, arranged in numerous small clusters and subtended by paired heart-shaped yellow-green bracts. Seeds/Fruit: Seeds are oblong, grayish to purple, contained in a 3-celled capsule. Leaves: Leaves are alternate, narrow, 1-4 inches long. Stems: Mature plants are up to 3 feet tall. Stems are thickly clustered. Roots: Extensive lateral root system. Seedling: Seed leaves (cotyledons) are linear to lanceolate, with entire margins. Other: The entire plant contains white, milky latex. Foliage of the plant is smooth and hairless. Impacts Agricultural: Leafy spurge can invade rangeland that is in excellent condition, making it worthless for cattle and horse grazing and reducing land values (Lajeunesse et al. 1999). Ecological: Leafy spurge is an aggressive, long-lived, perennial weed that tends to displace all other vegetation in rangeland, pasture, and native habitats (Biesboer 1998). Leafy spurge decreases rangeland diversity, threatens native plants and degrades wildlife habitat (Lajeunesse et al. 1999). It produces a large number of seeds and underground shoot buds. These two reproductive techniques allow it to rapidly displace native species, and form a leafy spurge monoculture. Rapid re-establishment of treated stands often occurs after an apparently successful management effort because of the large nutrient reserve stored in the roots of leafy spurge plants. Also, leafy spurge produces an allelopathic compound that inhibits the growth of other plants (Butterfield et al. 1996). Human: The milky latex associated with leafy spurge can cause irritation, blotching, blisters, and swelling in sensitive individuals. Habitat and Distribution General requirements: Leafy spurge grows in a wide range of habitats. It is most aggressive in semi-arid areas, but can be found in arid to subhumid and subtropic to subarctic habitats (Butterfield et al. 1996). Leafy spurge occurs most commonly on untilled, non-crop areas such as rangeland, pastureland, woodland, prairies, roadsides, stream and ditches, and waste sites. It grows on all kinds of soils, but is most abundant in coarse-textured soils and least abundant on clayey soils (Butterfield et al. 1996). Distribution: In Colorado, leafy spurge is common on disturbed or cultivated soils between 5,000 to 6,500 ft (Rutledge and McLendon 1998), but can be found up to 9,000 feet. Biology/Ecology Life cycle: Leafy spurge is one of the earliest plants to emerge in the spring, usually in mid-April to late May (Butterfield et al. 1996). The development of terminal flower clusters begins 1 to 2 weeks after stem emergence. Flower clusters have 8 to 16 branches. Each branchlet forms a greenish yellow bract in May. Flowering generally ends in late June to mid-July as the plants do not usually flower, and growth is reduced, during the hotter portion of the summer. However, if conditions are favorable, leafy spurge may produce a few lateral flowers throughout the summer and in the fall. Thus, it is possible for the plant to produce seed until frost. Seeds mature about 30 days following pollination. Peak germination occurs from late-May to early June. If adequate moisture is present, germination can occur throughout the growing season. Mode of reproduction: Despite being a successful seed producer, leafy spurge primarily reproduces vegetatively through its extensive lateral root system. Long roots have the capability to produce shoots and can reach nearly 15 feet laterally, and about 30 feet in depth. As many as 300 buds have been counted on these long roots (Butterfield et al. 1996). Seed production: Each flowering stem produces from 10-50 capsules with a seed yield range of 200-250 seeds per flowering shoot (Best et al. 1980). A large plant may produce up to 130,000 seeds (Rutledge and McLendon 1998). Seed bank: Seeds can remain viable in the soil for 5-8 years although 99% of the viable seeds will germinate in the first two years (Butterfield et al. 1996). Dispersal: The three-sided capsules explode when ripe, sending the enclosed seeds up to 15 feet from the parent plant. Seeds float on water, and can be transported and deposited by flood water. Note of Caution: The milky latex associated with leafy spurge can cause irritation, blotching, blisters, and swelling in sensitive individuals. The eyes should never be rubbed until after the hands are thoroughly washed. Gloves should be worn while pulling or coming into contact with this plant (suggested cultural controls or ways to prevent spread) Integrated Management Summary Persistent monitoring of areas with known or potential infestations is crucial to managing leafy spurge. New infestations are much more easily controlled than established infestations. 100% eradication of leafy spurge is rarely achieved, but infestations can be reduced to manageable levels. Herbicides are most commonly used to control leafy spurge. However, damage to non-target species is always a concern. Sheep and goats can be used to control leafy spurge. Leafy spurge is extremely difficult to control by chemical means and is almost impossible to control by cultural or physical methods. Therefore a management scheme that combines control methods over four to five years is recommended (Beck 1996). Lynn (1998) recommends combinations of re-seeding with competitive grasses, biological control insects, sheep or goat grazing and herbicide (2,4-D + picloram) treatment. Grazing animals and biological agents are generally appropriate only for larger infestations. Leafy spurge apparently has the ability to purge undesirable chemicals from the root system in approximately the top 18 in (45 cm) of the soil (Rees et al. 1996). This allows the remaining portion of the roots system to regenerate as soon as the effect of the chemical in the soil has dissipated (Rees et al. 1996). Although leafy spurge can be poisonous to cattle, sheep can be taught to feed on it and goats will seek it out. CONTROL References
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