Key identifying traits
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Leaves are alternate toothed and
pinnately divided
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Stems grow 3-7’ tall and are
swollen at the base
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Flowers are white and in
compound umbels
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Each flower has 2 seeds which
are kidney shaped and tea-colored
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The plant is easily identified
if the taproot is divided horizontally as it contains chambers
full of juice but BEWARE! The
juice is highly poisonous to animals and humans
Biology and ecology
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A perennial plant spreading by
seed
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It is considered one of the most
toxic plants in North America; has been mistaken for edible
members of the parsley family and responsible for several deaths
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Western waterhemlock is a native
of the intermountain region of the U.S.
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It
is a wetland plant often growing on streams and irrigation
canals as well
Control
Prevention –
Learn to identify plants; start monitoring early in the season
Biological –
No known biological control in our area
Cultural –
Plant competitive grass or other cover crop
Mechanical –
Care must be taken with any mechanical control especially cutting
mowing or digging when the juice may be ingested
Chemical –The
PNW Weed Management handbook lists MCPA or 2,4-D as chemical
recommendations; glyphosate
or dicamba should also work well on this weed
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Photo: Richard Old,
www.xidservices.com
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