Long lived, deep rooted perennial. Light muted green, with finely pubescent leaves, makes the plant appear dusty. Light lavender to purple flowers are borne at stem ends beginning in June and continuing until frost. Seed head bracts are smooth and papery. Produces a lot of seeds, however most are not viable and seedlings are uncommon. Spreads mostly by root shoots from rhizomes. Roots have a black papery bark layer. Grows from 1 to 2 feet tall, on openly branched stems. Forms very dense usually concentric stands and appears to exhibit allelopathic characteristics, effectively preventing other plants from growing in proximity, even it own seedlings. This plant is toxic to horses causing a neurologic disorder (chewing disease), however it seems to be unpalatable.

This plant can be very difficult to control. Mechanical means are not recommended because of the rhizomatous characteristic. Chopped and scattered root fragments can generate new plants, quickly making the situation worse. Herbicides are the preferred and most effective method. Fall applied Picloram (Tordon 22K, Outpost 22K) or Aminopyralid (Milestone) have been the most effective. It is recommended that you seek expert advice to manage this plant and use caution when treating with these chemistries as they both have a long residual effect. If the infestation has been on site for a few years, expect control to be difficult but not impossible.
‍
Modified from Selected Noxious Weeds of Eastern Oregon, Gary Page, Malheur County Weed Inspector.