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: Redroot pigweed
Photo by: D.G. Swan
  
Weeds : Redroot pigweed (Rough pigweed) : Amaranthus retroflexus
(revision date: 9/3/2015)

Family: Amaranthaceae
Cycle: Annual
Plant Type: Broadleaf

Use Integrated Pest Management (IPM) for successful weed management.

Biology
Redroot pigweed is a coarse, erect plant, growing two to three feet tall. The lower stems and branches and the upper portion of the taproot are frequently red or striped with red. Leaves are alternate, with long petioles and distinct veins. Branches or small flower clusters typically occur in the leaf axils. The majority of the flower clusters are at the top of the plant and appear as greenish, somewhat prickly, bushy-looking spikes. The small seeds are black and shiny. Redroot pigweed reproduces only via seeds, which can germinate any time conditions are favorable.
Habitat
Redroot pigweed is a common weed of gardens, cultivated areas, and waste places. Rarely, pigweed can become a lawn weed, where mowing will force it to lie close to the ground rather than growing upright. Redroot pigweed is widely distributed.

Management Options

Non-Chemical Management
  • Maintaining a healthy planting or turf area to provide competition will prevent weed establishment.
  • Cultivation (rototilling or hoeing) will effectively eliminate plants.
  • Hand-pull to eliminate weeds.
  • Mowing to prevent seed production is a very effective means of management. In lawns, mowing regularly at the proper height for the grass species may help minimize weed growth and invasion.
  • Careful digging is useful to manage weed populations. However, digging can carry undesirable weed seed to the surface and foster further germination.
Select non-chemical management options as your first choice!

Chemical Management

Apply according to label directions. Glyphosate and glufosinate products should be applied as spot treatments only! 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
  • glyphosate
  • dichlobenil
  • oryzalin
  • glufosinate
  • trifluralin
  • products containing diquat
Turf areas
  • products containing 2,4-D
  • products containing MCPA
  • triclopyr
  • 2,4-D + MCPP + dicamba
Bare ground areas
  • glyphosate
  • oryzalin
  • products containing diquat
  • products containing 2,4-D
  • triclopyr
Images

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Caption: Redroot pigweed
Photo by: D.G. Swan
Caption: Redroot pigweed leaves
Photo by: R. Parker
Caption: Redroot pigweed flower spike
Photo by: J.A. Kropf
Caption: Redroot pigweed flowers
Photo by: D.G. Swan
Caption: Redroot pigweed seedling
Photo by: J.A. Kropf
Caption: Powell amaranth mature seedhead
Photo by: T. W. Miller
Caption: Redroot pigweed showing distinct veins
Photo by: T. W. Miller