Ageratina altissima (Linnaeus) R.M. King & H. Robinson. Common White Snakeroot, Common Milk-poison. Phen: Late Jul-Nov. Hab: Moist forests, such as cove forests. Mesic forests, successional and disturbed forests, old fields. Dist: QC west to se. ND, south to Panhandle FL and c. TX.

Origin/Endemic status: Native

Taxonomy Comments: Var. angustata (A. Gray) Clewell & Wooten is sometimes recognized, and ranges from IL and e. KS south to LA and c. TX.

Other Comments: This species has been shown to be the cause of the "milk sickness" of pioneer days; the plants contain a poison which is transmissible to humans through cow milk.

Synonymy: = K4, Lamont (2018); = Ageratina altissima (L.) R.M.King & H.Rob. var. altissima – Ar, FNA21, K1, K3, NE, NY, Pa, Tn, Va; = Eupatorium rugosum Houtt. var. rugosum – C, SE1; = Eupatorium urticifolium Reichard – S; < Ageratina altissima (L.) R.M.King & H.Rob. – Fl7, Il, Mi, Ok, WH3; >< Ageratina altissima (L.) R.M.King & H.Rob. var. altissima – Clewell & Wooten (1971); > Ageratina altissima (L.) R.M.King & H.Rob. var. angustata (A.Gray) Blake – Clewell & Wooten (1971); < Eupatorium rugosum Houtt. – G, GrPl, NcTx, Oh3, RAB, Tat, Tx, W; > Eupatorium rugosum Houtt. var. chlorolepis Fernald – F; > Eupatorium rugosum Houtt. var. rugosum – F; > Eupatorium rugosum Houtt. var. tomentellum (B.L.Rob.) Blake – F

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Wetland Indicator Status:

• Atlantic and Gulf Coastal Plain: FACU
• Eastern Mountains and Piedmont: FACU
• Great Plains: UPL
• Midwest: FACU
• Northcentral & Northeast: FACU

Heliophily ?: 3