502 COMPOSITAE (COMPOSITE FAMILY) 
Means of control 
Prevent seed production by cutting the scapes while in bloom. 
The weed grows only on clay soil and likes it moist; drainage, lim- 
ing, manuring, and enriching the ground enables better plants to 
crowd it out. The horizontal rootstocks grow so near the surface 
that cultivation turns them out, when they may be readily raked 
away and removed. 
SWEET COLTSFOOT 
Petasites palmdatus, Gray 
Native. Perennial. Propagates by seeds and by rootstocks. 
Time of bloom: April to June. 
Seed-time: May to July: 
Range: Newfoundland to British Columbia and Alaska, southward 
to Massachusetts, New: York, Michigan, and Minnesota. 
Habitat: Recently cleared ground, wet meadows, and swamps. 
Scapes stout, appearing before the leaves, very scaly, and vary- 
ing in height from about six inches when in first bloom to nearly 
two feet when mature. Heads in corymbose terminal clusters, 
each less than a half-inch broad, pale yellow or cream-color, and 
fragrant ; they are partly dicecious, the fertile plants having heads 
almost wholly pistillate, with one or more outer rows of ray 
florets; the perfect but sterile flowers have tubular five-cleft 
corollas with undivided styles. Leaves finally very large, often 
more than a foot broad, rounded, palmately and very deeply lobed, 
with five to seven segments also cut and toothed, glossy and deep 
green above but densely white-woolly below especially when young. 
Rootstocks very large and thick. 
Like Tussilago, this weed is driven out by drainage and culti- 
vation. 
BUTTERFLY DOCK 
Petasites vulgaris, Hill 
Other English names: Butter Dock, Flea Dock, Poison Rhubarb, 
Oxwort, Pestilence Wort, Umbrella Leaves. : 
Introduced. Perennial. Propagates by seeds and by rootstocks. 
Time of bloom: April to May. 
Seed-time: Late May to June. 
