Common and Scientific Names of Weeds in Floriculture and Nurseries

Weeds are broadly divided into broadleaf plants (dicotyledons) or narrowleaf plants (monocotyledons). Most narrowleaf plants are grasses, but this group also includes sedges, such as yellow nutsedge, which are important weeds. Another way to classify weeds is by when they germinate and grow. Many common weed species are winter annuals, germinating mainly in fall, growing through winter and spring, and dying as summer approaches. Summer annuals germinate in spring, grow through summer and die as the temperature drops in the fall. Irrigation can alter the germination time of weeds and prolong the life span of some annuals and delay their senescence. A few weeds complete a life cycle in 2 years and are referred to as biennials (e.g., bristly oxtongue). Some of the worst weed species are perennials; weeds that live for 2 years or more. These include bermudagrass, creeping woodsorrel, and nutsedge that persist through their vegetative propagules (stolons, rhizomes, or tubers). See the Common Weeds in Floriculture and Ornamental Nurseries table for a list of these and links to photographs and more information on them.

Growing site and production practices largely determine which weeds are likely to become problems at a site. For example, weeds commonly associated with container nursery production include creeping woodsorrel, common groundsel, lesser-seeded bittercress, northern willowherb, and prostrate and spotted spurge. Sometimes annual bluegrass, liverwort, or pearlwort are a problem. In greenhouses, weeds that thrive in moist conditions often proliferate. These include liverwort, mosses, and pearlwort. In field sites, weed species vary greatly but the weed spectrum can be influenced by management practices in the field and by the environment. Because of these variations, each type of production situation is addressed separately in this guideline. After the section on general methods of weed management, there are special sections for weed management in

• container nurseries
• field-grown trees and shrubs
• field-grown flowers
• greenhouse-grown crops