The Enemy: Orange sneezeweed (Hymenoxys hoopesii)

Strategy: This native plant of the Pacific Northwest can become invasive. It is usually found above 4,000 feet elevation in meadows and open range. This herbaceous plant grows to about 2.5 feet tall. It bears oblong, lance-shaped leaves at its base and the leaves get smaller as you look up the stems. The stems produce a yellow-orange cluster of ray flowers at their top, usually flowering in late July to early August. It has mostly a fibrous root system but has short rhizomes.

Attack: Typically this native plant minds its own business in meadows and rangeland. If a site gets over grazed, this plant can spread rapidly. According to the USDA ARS Logan Poison Plant Lab, it causes respiratory and digestive tract irritation known as spewing sickness. As animals graze the area, they select the more desirable plants, which increases the infestation of the orange sneezeweed.

Defense: Grazing management, thus reducing the disturbance, will usually keep this plant from changing from a native plant to an invasive weed. Mostly, one will not recognize this plant as a weed until its beyond reasonable control with a shovel, but mechanical control can be utilized if you find one or two of these plants. Early work in the 1940s was done on this plant using 2,4-D at 1 gallon per acre. I would not go over 2 quarts in the spring. New chemistries such as Milestone (6 ounces/acre) or Opensight (3.3 ounces/acre) when the plants are in the bud stage or after a killing frost in the fall are best. Opensight may be hard some of the brush species. If you want more selection and less off-target damage, use Milestone.

To learn more, call Bonneville County Weed Superintendent Jeffrey Pettingill at 208-529-1397 or email weeds@co.bonneville.id.us.

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