906 Compositae Eupatorium 



Florets 5-7, rarely 3, 4, or 8; inflorescence convex; stems more or less glaucous. 

 Stems hollow, plainly glaucous, purple (except when growing in dense shade), not 

 darker at the nodes; flowers generally pinkish purple, sometimes greenish 



yellow 2. E. fistulosum. 



Stems solid (with a pith), rarely hollow toward the base, faintly glaucous, green 

 with the nodes generally purplish; flowers generally greenish yellow, rarely 



pinkish purple 3. E. purpureum. 



Leaves opposite (rarely ternate or the upper alternate); plants generally less than 

 1.5 m high. 

 Involucral bracts imbricated in 2 or more series, the outer shorter. 

 Involucral bracts oblong, obtuse. 

 Heads 12-15-flowered. 



Leaves, at least the lower, slender-petioled, 3-nerved; achenes less than 2 mm 



long 4. E. serotinum. 



Leaves sessile, the cuneate base entire, many-nerved; achenes more than 



2 mm long 4a. E. serotinum var. polyneuron. 



Heads 5-flowered. 



Leaves strongly 3-nerved, long-tapering at the base 5. E. altissimum. 



Leaves pinnately veined, rounded and sessile at the base. . . 6. E. sessilifolium. 

 Involucral bracts lanceolate, acute. 

 Flowers white. 



Leaves connate-perf oliate 7. E. perfoliatum. 



Leaves not connate-perfoliate. 



Leaves, at least the upper, truncate or rounded at the base 



7a. E. perfoliatum f. truncation. 



Leaves cuneate at the base, sessile, smaller than in the species or other 



forms 7b. E. perfoliatum var. cuneatum. 



Flowers purplish I.E. perfoliatum f . purpureum. 



Involucral bracts in 1 or 2 series, all equal or nearly so. 



Flowers white; leaves ovate, large, thin, generally abruptly narrowed at the base, 



or rarely truncate or subcordate; bracts generally obtuse 8. E. rugosum. 



Flowers pink or violet purple; leaves ovate or deltoid-ovate, truncate, cordate, 

 subcordate, or shortly narrowed at the base. 

 Receptacle flat; leaves deltoid-ovate; outer bracts mostly less than half as long 



as the inner, acute 9. E. incarnatum. 



Receptacle conical; leaves ovate; outer bracts nearly as long as the inner ones, 

 long-acuminate 10. E. coelestinum. 



1. Eupatorium maculatum L. (Wiegand. Eupatorium purpureum and 

 its allies. Rhodora 22 : 57-70. 1920 and Wiegand & Weatherby. The nomen- 

 clature of the Verticillate Eupatoria. Rhodora 39: 297-306. 1937.) 

 Spotted-stem Joe-pye-weed. Map 1982. In wet ground or springy places 

 along streams and ditches, about lakes, and in marshes and wet woods 

 throughout the lake area of the state. South of this area it is rare 

 or absent. 



The Joe-pye-weeds have been misunderstood, and all or most all of the 

 reports should be ignored, because, as far as I know, none of our authors 

 knew of the existence in our area of three species of this group or had keys 

 which would separate them. 



Newf., Que., Mich, to B. C, southw. to Pa., 111., and N. Mex. 



2. Eupatorium fistulosum Barratt. PURPLE-STEM Joe-PYE-WEED. Map 

 1983. Infrequent to frequent in springy and wet places in woods and along 

 streams in the southern half of the state. Formerly I did not recognize the 



