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Poison Hemlock
Apiaceae (=
Umbelliferae), the parsnip family
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Background
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 Poison
hemlock is native to Europe. It contains highly poisonous alkaloids toxic to
all classes of livestock and humans. It has poisoned many who have mistaken
it for parsley. Poison hemlock is often found on poorly drained soils,
particularly near streams, ditches, and surface water.
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Description
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 Poison
hemlock is a biennial that grows up to 10 feet
tall. Stems are stout, hollow, ridged, and mottled with purple spots. Leaves
are shiny green, 3 to 4 times pinnately compound, and
clasp the stem at the
obvious nodes. Crushed foliage has a disagreeable, mousey odor. Flowers are
small, white, and borne in umbrella-shaped clusters about 3 inches across
in early summer. Seeds are ridged and flattened, with 2 seeds borne
together. The plant has a thick, white
taproot.
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Distribution
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 It
grows throughout the U.S. except from eastern Montana to northeastern
Minnesota and south to Nebraska. It has an extensive presence in Idaho. |
Control
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A biological control agent (a
defoliating moth) provides good to excellent but inconsistent control.
Herbicides are also available.
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© 1999 University of Idaho:
Text and photographs for these pages from Idaho's Noxious Weeds, by
Robert H. Callihan and Timothy W. Miller (revised by Don W. Morishita
and Larry W. Lass).
Please contact: Ag Publishing, University of Idaho, Moscow,
Idaho 83844-2240; 208 882-7982 visit the Resources for Idaho website at
http://info.ag.uidaho.edu, for more information about this or other
publications.
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Perennial Pepperweed
(broad-leaved peppergrass, tall whitetop, Virginia pepperweed)
Brassicaceae
(= Cruciferae), the mustard family
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Background
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 Perennial pepperweed is native to southern Europe and
western Asia. It spreads by seed and creeping roots under many different
environmental conditions.
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Description
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 Perennial pepperweed grows up to 6 feet tall and has
basal leaves that
are lance shaped, have long petioles, are up to 12 inches long, and are
covered with a waxy layer. Stem leaves are smaller and have shorter
petioles, but don't clasp the stem. Leaves have a prominent, whitish
midvein. Flowers are white, less than 1/6 inch wide, and develop in dense,
rounded clusters at the branch tips from early summer until fall. Fruits are
roundish, slightly hairy, measure 1/16 inch in diameter, and contain 2 tiny
seeds.
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Distribution
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 Perennial pepperweed is widely scattered throughout the
U.S. and in many Idaho counties. |
Control
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No biological control agents are available for perennial
pepperweed, but herbicides are available to provide control.
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© 1999 University of Idaho:
Text and photographs for these pages from Idaho's Noxious Weeds, by
Robert H. Callihan and Timothy W. Miller (revised by Don W. Morishita
and Larry W. Lass).
Please contact: Ag Publishing, University of Idaho, Moscow,
Idaho 83844-2240; 208 882-7982 visit the Resources for Idaho website at
http://info.ag.uidaho.edu, for more information about this or other
publications.
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