WSU Extension

Hortsense

Weeds
 
Annual bluegrass 
Barnyardgrass 
Bentgrass, creeping 
Bermudagrass 
Bittercress (Shotweed, Hairy bittercress) 
Bittersweet nightshade (European bittersweet) 
Black medic 
Blackberry (Himalayan, Evergreen, Pacific) 
Blue mustard (Purple mustard, Tenella mustard) 
Brackenfern, western 
Buffalobur 
Bull thistle 
Buttercup, creeping 
Canada thistle 
Catchweed bedstraw (Cleavers) 
Catsear, common (False dandelion) 
Chickweed, common and mouseear 
Clover 
Comfrey 
Crabgrass 
Dandelion 
Dock (Curly, Broadleaf) 
Dodder 
Downy brome (Cheatgrass, Downy chess) 
Dwarf mistletoes 
English daisy (Lawn daisy) 
English ivy 
Field bindweed (Wild morningglory) 
Field pennycress (Fanweed) 
Flixweed 
Foxtail (Green, Yellow, Bristly) 
Garden loosestrife 
Giant hogweed 
Goldenrods 
Groundsel, common 
Hawkweeds 
Hedge bindweed 
Henbit 
Herb Robert (Robert geranium, stinky Bob) 
Horsetails (Scouringrush) 
Horseweed (Marestail) 
Knapweeds 
Knotweeds (Bohemian, Giant, Japanese, Himalayan) 
Kochia 
Lambsquarters, common 
Liverworts 
Mallow, common (Cheeseweed, Buttonweed) 
Nightshades 
Oxalis (Creeping woodsorrel) 
Parrotfeather and Eurasian watermilfoil 
Pineappleweed 
Plantain (Broadleaf, Buckhorn) 
Poison hemlock 
Poison ivy and Poison oak 
Prickly lettuce (China lettuce) 
Prostrate knotweed 
Puncturevine (Tackweed, Goathead) 
Purple deadnettle (Red deadnettle) 
Purple loosestrife (Purple lythrum) 
Purslane, common 
Quackgrass 
Red sorrel (Sheep sorrel) 
Redroot pigweed (Rough pigweed) 
Redstem filaree (Stork's bill, Crane's bill) 
Reed canarygrass 
Russian thistle (Tumbleweed) 
Ryegrass, annual (Italian ryegrass) 
Salsify (Goatsbeard) 
Scotch broom 
Shepherd's-purse 
Smartweeds 
Sowthistle, annual and perennial 
Speedwells 
Spurges (Prostrate spurges) 
St. Johnswort, common (Goatweed, Klamathweed) 
Stinging nettle 
Tansy ragwort 
Tumblemustard (Jim Hill mustard) 
Velvetgrass (Common velvetgrass) 
Velvetleaf 
Water primrose 
Waterhemlock, western 
Yellow nutsedge 



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Caption: Western waterhemlock flower clusters
Photo by: R. Parker
  
Weeds : Waterhemlock, western : Cicuta douglasii
(revision date: 9/3/2015)

Family: Apiaceae (Umbelliferae)
Cycle: Perennial
Plant Type: Broadleaf

Biology
Western waterhemlock begins growth in the spring. The tall, branching plants reach three to seven feet high by late spring to early summer, when flowering begins. The hollow, erect stems are swollen at the base and into the roots. The swollen, finger-like roots are typically divided into chambers by horizontal walls. Long-stemmed leaves are alternate on the branches, and are typically divided into several slender, pointed leaflets. Each leaflet is toothed, with the veins ending in the bottoms of the serrations instead of at the tips. This characteristic differentiates waterhemlock from other plants in the carrot family. Tiny white flowers occur at the tips of the branches in rounded, stalked, umbrella-shaped clusters. SPECIAL INFORMATION: This plant is extremely poisonous (particularly the taproot) and should be handled with caution, as there is no known treatment. The horizontally-chambered taproot is a distinctive feature of the species but may not be as apparent in young plants.
Habitat
Western waterhemlock grows in moist areas (along streams and ditches, in marshy areas, wet fields, etc.). It is considered one of the most poisonous plants in North America.

Management Options

Non-Chemical Management
None recommended
Select non-chemical management options as your first choice!

Chemical Management

None recommended; not a problem in healthy established turf. NOTE: Some ingredients listed here are only available in combination. Read the label carefully on combination products to make sure the product is suitable for your specific situation.

Landscape areas
    Turf areas
    • 2,4-D + MCPP + dicamba
    Bare ground areas
      Images

      + Show larger images

       
      Caption: Western waterhemlock flower clusters
      Photo by: R. Parker
      Caption: Western waterhemlock leaves
      Photo by: R. Parker
      Caption: Western waterhemlock root cross-section
      Photo by: R. Parker
      Caption: Western waterhemlock flowers and leaves
      Photo by: N.R. Ness