. ▁Despite ▁having ▁decl ined ▁over ▁time , ▁several ▁populations ▁of ▁the ▁plant ▁contain ▁many ▁thousands ▁of ▁individuals . ▁Pop ulations ▁vary ▁depending ▁on ▁the ▁amount ▁and ▁duration ▁of ▁flo oding ▁that ▁occurs ▁in ▁the ▁area ▁each ▁year . ▁The ▁plant ▁is ▁a ▁feder ally ▁listed ▁threatened ▁species . ▁ ▁This ▁plant ▁was ▁long ▁treated ▁as ▁a ▁variety ▁of ▁Bol ton ia ▁astero ides ▁until ▁ 1 9 8 5 , ▁when ▁it ▁was ▁elev ated ▁to ▁species ▁status , ▁a ▁status ▁it ▁had ▁held ▁once ▁before . ▁It ▁is ▁a ▁bush y ▁per enn ial ▁her b ▁spraw ling ▁to ▁ 1 . 5 ▁meters ▁in ▁height , ▁often ▁exceed ing ▁two ▁meters . ▁The ▁leaves ▁are ▁dec urrent , ▁their ▁bases ▁extending ▁down ▁the ▁stem ▁at ▁their ▁attachment . ▁The ▁bl ades ▁are ▁up ▁to ▁ 1 5 ▁cent im eters ▁long ▁and ▁linear ▁or ▁lance - sh aped . ▁The ▁infl ores c ence ▁is ▁a ▁large ▁pan icle ▁of ▁leaf y ▁branches ▁and ▁many ▁flower ▁heads ▁with ▁white ▁or ▁pale ▁pur ple ▁ray ▁flor ets ▁meas uring ▁ 1 ▁to ▁ 2 ▁cent im eters ▁long . ▁The ▁center ▁contains ▁many ▁yellow ▁disc ▁flor ets . ▁Flow ering ▁occurs ▁in ▁August ▁through ▁October . ▁The ▁plant ▁reprodu ces ▁veget atively ▁by ▁growing ▁new ▁sho ots ▁and ▁sex ually ▁by ▁making ▁seed . ▁The ▁species ▁produces ▁a ▁large ▁amount ▁of ▁se eds , ▁aver aging ▁ 5 0 , 0 0 0 ▁per ▁plant . ▁The ▁se eds ▁are ▁dispers