Tall whitetop, Tall pepperweed, Perennial pepperweed, Giant whiteweed, Perennial peppergrass, Slender perennial peppergrass, Broadleaf pepperweed, Ironweed
FULL SCIENTIFIC NAME
Lepidium latifolium L.
FAMILY NAME COMMON
FAMILY SCIENTIFIC NAME
Synonyms: Cardaria latifolia (L.) Spach
Lepidium latifolium is an herbaceous perennial that can grow up to 1.5 m (5 ft.) tall. Plants emerge from thick, minimally branched roots or semi-woody crowns. Individuals remain as a rosette for several weeks before the stem elongates. Rosette and basal leaves tend to senesce as the top of the plants develops. The above ground parts begin to die back in late summer or early fall. Dead stems can persist for several years. Lepidium latifolium flowers in early summer, continuing through most of the growing season; fruits are produced in the late summer and fall. Plants have a horseradish taste and odor. Stems and foliage are glaucous (waxy grayish-green) and tend to be glabrous, although they can sometimes be hairy. Rosette leaves are up to approximately 30 cm (11.8 in.) long and 8 cm (3 in.) wide with serrate margins and 3-15 cm (1.2-6 in.) long petioles. The cauline leaves are alternate, sessile and significantly reduced. They taper at the base, are lanceolate to elliptic or oblong and have entire or weakly serrate margins. The flowers of Lepidium latifolium are densely clustered in terminal panicles. There are 4 small, green, oval sepals; 4 white, ovate petals approximately 1.5 mm (0.06 in.) long; 6 stamens and a single pistil which gives rise to a small (2 mm (0.08 in.)) round capsule (silicle), with a single slightly flattened reddish-brown seed in each chamber. Seedlings are not usually observed in the wild. Page References Fernald 702, Gleason & Cronquist 181, Holmgren 165, Magee & Ahles 553. See reference section below for full citations.
The seeds of Lepidium latifolium are mechanically dispersed, but few seedlings have been observed in the field. Local spread is achieved vegetatively through rhizomes.
Lepidium latifolium is native to southeast Europe, North Africa and southwest Asia. It is reported as a non-native in northern Europe and has invaded Australia. It is known to occur in three Canadian provinces. In the United States, infestations have been reported in all states west of the Rocky Mountains. In New England it occurs in Massachusetts, Connecticut and New Hampshire. It is considered Restricted and Invasive in Connecticut.
HISTORY OF INTRODUCTION IN NEW ENGLAND
Lepidium latifolium was first reported as an escapee in New England from Peabody, Massachusetts (Essex County) in 1924 near the American Glue Company. There is speculation that its introduction at this site may have been through glue-stock. In Connecticut, it was first reported in 1933 from near the site of a dye and licorice works in Noroton (Fairfield County) where it "spread greatly on the shore in the past year" and "in one summer has already covered a large marshy field and is spreading all over the place." A population along the Massachusetts Turnpike in Auburn (Worcester County) was first observed in 1997. Its occurrence in New Hampshire was published in 2006.
HABITATS IN NEW ENGLAND
Abandoned Field, Agricultural Field, Coastal Beach or Dune, Coastal Grassland, Herbaceous Wetland, Pasture, Roadside, Salt Marsh, Vacant Lot, Wet Meadow, Yard or Garden. In New England, infestations of Lepidium latifolium are mainly found near the coast and on coastal islands. It often occurs at the upper edges of salt marshes above the high tide line, frequently forming dense stands. It also occurs well removed from the coast (for example along the Massachusetts Turnpike in Worcester County, MA), where it grows in disturbed areas near roads.
Lepidium latifolium has the ability to form dense stands of plants that can increase in size over time. It grows at the upper edge of salt marshes and can be dispersed by animals, humans or vehicles that pass through these stands. Its seeds have been shown to remain viable even after being in salt water, implying that they can also disperse by tidal currents. Lepidium latifolium appears to out-compete other species that naturally occur in these habitats. Its establishment along highways suggests that it may disperse away from the coast and into minimally managed habitats and disturbed areas elsewhere in the region.
Plant Conservation Alliance Fact sheet including management information
Documentation needs:A photograph showing the plant and its overall habit, so that the size of the plant can be determined.
Integrated Taxonomic Information System Taxonomic information
The PLANTS Database General information and a map
Montana State University General and control information
Blank, R. R. and J.A. Young. 1997. Lepidium latifolium: Influences on soil properties, rate or spread, and competitive stature. Pp. 69-80. In Brock, J.A., M. Wade, P. Pysek and D. Green, eds. Plant Invasions: Studies from North America and Europe. Backhuys Publishers Leiden, The Netherlands.
Bossard, C.C., Randall, J.M., and Hoshovsky, M.C. (2000) Invasive plants of California's wildlands. University of California Press, Berkeley, California.
Chen, H., Qualls, R.G., and Miller, M.C. (2002) Adaptive responses of Lepidium latifolium to soil flooding: biomass allocation, adventitious rooting, aerenchyma formation and ethylene production. Environmental and Experimental Botany 48, 119-128.
Eames, E. H. 1935. Lepidium latifolium in Connecticut. Rhodora 37:161-162.
Fernald, M.L. 1950. Gray's Manual of Botany 8th ed. American Book Co., Boston.
Orth, J.F., M. Gammon, F. Abdul-Basir, R.D. Stevenson, D. Tsirelson, J. Ebersole, S. Speak, R. Kesseli. 2006. Natural history, distribution, and management of Lepidium latifolium (Brassicaceae) in New England. Rhodora 108: 103-118
Gleason H.A. and A.C. Cronquist. 1991. Manual of Vascular Plants of the Northeastern United States and Adjacent Canada. 2nd ed. New York Botanical Garden, Bronx, New York.
Holmgren N.H. 1998. Illustrated Companion to Gleason and Cronquist's Manual. New York Botanical Garden, Bronx, New York.
Magee D.W and H.E. Ahles. 1999. Flora of the Northeast. University of Massachusetts Press, Amherst.
Mehroff, L.J. 2000. Immigration and expansion of the New England Flora. Rhodora 102:280-298.
Miller, G.K., J.A.Young, R.A. Evans. 1986. Germination of seeds of perennial pepperweed (lepidium-latifolium). Weed Science 34 (2): 252-255.
Morse, A.P. 1924. Lepidium latifolium in New England. Rhodora 26:197-198.
USDA, NRCS. 2001. The PLANTS Database, Version 3.1. (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Young, J.A., D.E. Palmquist, R.R. Blank. 1998. The ecology and control of perennial pepperweed (Lepidium latifolium L.). Weed Technology 12 (2): 402-405.
Young, J.A. and D. E. Palmquist and S. O. Wotring. 1997. The invasive nature of Lepidium latifolium: A review. Pp. 59-68. In Brock, J.A., M. Wade, P. Pysek and D. Green, eds. Plant Invasions: Studies from North America and Europe. Backhuys Publishers, Leiden, The Netherlands.