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Key identifying traits
Deeply lobed watermelon type leaves
Yellow, 5-lobed flowers throughout summer
1/8-1/2" yellow spines cover all parts of plant including stems, leaves and round seed pods
Seeds are nearly round, up to 1/2" in diameter & reddish brown to
brown in color
Grows up to 2'tall with erect stem and ascending branches
Biology and ecology
- An annual with a tap root
- Native to U.S. but not to Washington State
- Common in some western wastelands and prairies
- Serves as a host for Colorado potato beetle
- Common on sandy soils but grows in most soils
- Occasionally found in gardens in our area probably introduced as a
seed contaminant
- Not a highly competitive species and may not reproduce well in our
climate
Control
Prevention –
Learn to identify plants; know your property;
beware of unusual or unintended plants in gardens and around bird feeders
Biological – none contemplated for this U.S. native; should have
natural enemies already in native areas
Cultural – Good competitive vegetative cover helps
Mechanical – Cultivation, pulling and repeated cutting all work
well; be careful to avoid puncture wounds from spines
Chemical – Several work well at label rates; care must be used if
in a garden site to avoid off target plant damage;
refer to the
PNW Weed Management Handbook for specific chemical recommendations
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