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Species
Information
- spikeweed
(common tarweed)
- Hemizonia
pungens (Hook. & Arn.) Torr. & Gray
- USDA
Symbol: HEPU5
- Oregon
Noxious Weed Designation: B
- Pictures
Identification: Annual; blooms July to September. Grows 1 1/2 to 3 ft tall. Basal leaves pale, straw colored, stiff and several inches long with narrow lobes. Stem leaves 1/2 in long or less and sharp pointed, bearing dwarf stems in their axils. Flower heads yellow, 1/3 in broad and borne at the tips of short leafy branches.
Impacts: Spikeweed is native to California. It is reported more frequently in central and eastern Oregon, occurring on roadsides, waste areas and in low alkaline sites of grain fields and rangelands. Spikeweed is a tough, spiny plant which is avoided by livestock. It is a heavy seed producer and forms dense stands on areas favorable to its growth.
Biological
Controls: No approved biological control agent is available.
Oregon
Maps of Spikeweed Distribution
Links:
USDA
Plants Database information on spikeweed
GRIN
Database information on spikeweed
Oregon Department
of Agriculture information on spikeweed
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