Description:
Clasping pepperweed (Lepidium latifolium).
Perennial pepperweed (synonym: Cardaria latifolia (L.) Spach), is also known as tall whitetop, giant whiteweed, perennial peppergrass, slender perennial peppercress, broadleaf or broadleaved pepperweed, ironweed and other names. Plants are multiple stemmed and grow in stiffly erect masses up to 5 ft. (1.5 m.) tall, sometimes taller. Leaves are lanceolate, bright green to gray green, and entire or toothed. Basal leaves are stalked, up to 1 ft. (30 cm) long and 3 in. (8 cm.) wide and have serrate margins. Stem leaves are smaller, ranging from 3-10 in (7-25 cm) in length, tapered at the base, entire to weakly serrate and are sessile to stalked. Flowering occurs from early summer to fall. Abundant small white 4-petaled flowers are borne in dense clusters near the stem tips. The fruits are small, flattened pods about 1/10th inch long, each containing 2 seeds (1 per chamber). Fruits remain on the plant, dropping irregularly throughout the winter. The base of the stem is semi-woody. The roots enlarge at the soil line, forming a woody crown. Root length is dependent on soil tilth, but can be up to 6 feet. Roots are creeping, with new plants springing from root sections as small as 2 inches. Seedlings, when present, have leaves that are ovate to oblong, ?-? inch long, with smooth to slightly wavy edges and a petiole approximately 1/5th inch long. Subsequent leaves resemble first leaves, but are larger in size.
Ecological Threat:
Perennial pepperweed is a highly invasive herbaceous perennial. It can invade a wide range of habitats including riparian
Clasping pepperweed (Lepidium latifolium) Distribution in North America shown in green.
areas, wetlands, marshes, and floodplains. It adapts readily to natural and disturbed wetlands. As it establishes and expands, the plants create large monospecific stands that displace native plants and animals. It addition to impacting alfalfa and pasture production, it has been reported to adversely affect food quality and nesting habitat for native birds and threaten the Carson?s Wandering Skipper butterfly. Most of the reports of habitat and food quality are anecdotal.
Biology & Spread:
Perennial pepperweed rarely produces seedlings in the field. There is no known reason for this, as laboratory tests have shown seed viabilities to be high. Seeds lack a hard seed coat and lose viability rapidly, suggesting that resurgence of a treated infestation from the seed bank would be low. The plant mainly propagates clonally from its brittle rhizome-like roots. Roots exposed by washouts and land disturbances fragment and move along riparian corridors to start new infestations downstream. Roots fragmented by the mechanical actions of land management practices increase infestation densities and facilitate spread.
Management:
Chemical:Foliar application Only foliar application methods have been shown to be effective. A list of herbicides, sites
Close up of Clasping pepperweed (Lepidium latifolium).
where the compound has been approved for use, restrictions, and effectiveness is included in the table. For rates and other important information, see the herbicide label. Herbicide Site Restrictions Effectiveness Telar? (chlorsulfuron) Noncrop Industrial Selective herbicide (will not harm most grasses), do not apply near water. Excellent control for 1-2 years Habitat? (imazapyr) Stalker?? (imazapyr) Riparian, Wetlands Wildlands Nonselective herbicide, do not apply near water. Excellent control for 1-2 years. Treated areas typically remain void of any vegetation for 1-2 years after treatment. Roundup? and others (glyphosate) Rodeo?, Aquamaster? and others (glyphosate) Wildlands Aquatic Nonselective herbicide. Rodeo? for areas near/in aquatic sites. Effective unless infestation is dense. If dense, mow area and apply to resprouting plants. Weedar 64? (2,4-D) Wildlands Aquatic Selective herbicide (will not harm grasses) Somewhat effective unless infestation is dense. If dense, mow area and apply to resprouting plants.
Manual: Mechanical control options are typically not effective. Very small patches can be controlled by hand removal if the process is repeated often for several years and plants are not allowed to mature. Because root systems are brittle and can extend so deep in the soil most mechanical techniques, such as disking, can spread the weed and increase the density.
Sourced From: http://www.texasinvasives.org/plant_database/detail.php?symbol=LELA2
