PCA Exam- Weeds

PCA Exam- Weeds What are weeds plants that interfere with the growing of crops or ornamental plants or cause other types of damage Invasive weeds cause ecological damage by displacing native plants and the organisms that feed on them; compete with ag crops for water and nutrients, causing them to become more susceptible to disease or other pests True weeds adapt well to local climates, soils, and other external conditions Perennial weeds capable of reproducing through vegetative structures such as stolons, rhizomes, and tubers; cultural activities such as hoeing, mowing, or discing can produce new plants; persistent and hard to eliminate; morning glory Native weeds 3% plants are weeds; no more than 25-35 weeds in one site Weeds and their affects Harbor insects, dry is fire hazard, reduce livestock forage quality and quantity, jeopardize animal and human health, increase the threat of fire or flooding, interfere with recreational activities, lower land value, change soil fertility, increase erosion, leaf litter IDing weeds recognize differences in flowers, leaves, stems, roots, fruit, seeds, and special structures such as tubers and rhizomes Dicots broadleaves, two seedling leaves (cotyledons), netlike veins, herbaceous or woody plant Monocots single grasslike leaf in seedling, veins that run parallel, grasses, sedges, and rushes Bryophytes mosses and liverworts; lack a vascular system; occasional pests Algae nonflowering aquatic plants that clog storm drains, stream, lakes, ditches and rice fields; carryout photosynthesis; lack true stems, leaves, and flowers; reproduce through cell division or production of spores Best weed stage to kill seedling Winter Annual germinate in the fall, mature in the winter, die in the early summer, seeds dormant till fall Summer Annual germinate in the spring, mature in the summer, die in the fall, seeds dormant till the spring Annual Weeds live 1 year or less Examples of summer annuals pigweed, puncturevine, barnyardgrass, russian thistle, common purslane, yellow foxtail Examples of winter annuals mustard, wild oat, annual bluegrass, burclover, filaree Biennial weeds live for two growing seasons; sprout and undergo vegetative growth during the first season, flower, produce seeds, and die following season Examples of biennial weeds bristly oxtongue, poison hemlock, wild carrot, mullien, scotch thistle Perennial weed examples curly dock, silverleaf nightshade, field bindweed, alkai sida, dandelion, yellow nutsedge, pacific poison oak, johnsongrass, bermudagrass Flowers contain sexual reproductive organs and differ widely among species; occur singly or compound inflorescences, groups of flowers arising from main stem Leaves arrangement and shape of leaves, vein patterns, and presence of spins or hairs are helpful identifying characteristics; grasses experts rely on collar region Stems weed's basic framework or skeleton; connect roots to other structures providing support for leaves and flowers as well as channels for transport of nutrients and water Rhizomes elongated underground stems that grow horizontally from the plant Tubers