This plant is extremely difficult to exterminate! A long lived deep rooted perennial herb. Spreads mainly by root shoots from rhizomes, but also reproduces from seed. Very small and nondescript yellow flowers appear in late May and are partially hidden in showy bright green bracts. Plants reach 1 to 3 feet tall and usually have a central stem with many radiating branches. Stems will be dull reddish near the soil surface and dull green above. Leave appear nearly opposite but in fact are alternate, lance shaped about ¼ inch wide and 3 inches long. All parts contain a viscous white latex into autumn. This latex can be very irritating and can cause blindness. It can be toxic to cattle and horses. Sheep and goats tolerate grazing, although without significant weight gain.

The combination of a deep root system and the viscous latex makes herbicide translocation throughout the plant exceedingly difficult. Picloram (Tordon) has been the traditional favorite. Imazapyr (Plateau) also works well.  Both can have long residual effect so use caution and follow the label.  Planting some variety of perennial grass can help reduce infestation. Mechanical removal is not recommended due to root shoot dispersal. Several effective insect biocontrols are available and have been released locally.
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Information from “Selected Noxious Weeds of Eastern Oregon,” by Gary Page, Malheur County Weed Inspector.