LEGUMINOSAE PULSE FAMILY 
SHOWY TICK TREFOIL 
Desmodium canadense (L.) DC. 
Of the dozen or more Tick Trefoils found in Illinois this is 
the-showiest. It grows in open woods and along streams and 
railroads from Nova Scotia to Manitoba and south to North 
Carolina and Oklahoma, and blooms from July 
to September. It is perennial, with stout hairy 
stems 2-8 feet high and bearing leaves which are 
somewhat hairy below but smooth above. The 
upper leaves are nearly sessile but the lower have 
petioles up to 1 inch long. 
The large, purple or bluish purple, conspicu- 
ous flowers are produced in a dense-branched 
inflorescence. The calyx is somewhat 2-lipped, 
with the upper lip 2-toothed and the lower 3- 
lobed. The corolla is butterfly shaped; the stand- 
ard and wings are oblong and the keel 1s nearly 
straight. Nine of the 
IO stamens are united. 
The pistil develops 
into a pod which when 
mature is nearly sessile 
in the calyx, about 1 
inch long and 3-5-joint- 
ed. Each triangular 
joint contains 1 seed 
and is covered with 
hooked hairs that en- 
able it to cling tena- 
ciously to clothing or 
to animals. 
The Hoary-leaved Tick Trefoil, Desmodium canescens (L.) 
DC., is another species quite common in Illinois, especially along 
railroads. It grows 3-5 feet high and is densely clothed with 
short, hooked hairs and also longer glutinous hairs that make 
the plant somewhat sticky. The 3 leaflets are 1-4 inches long, 
about equaling the petiole, and the terminal leaflet is usually 
somewhat larger than the other 2. 
The Illinois Tick Trefoil, Desmodium illinoense Gray, is simi- 
lar to the Showy Tick Trefoil but may be distinguished by its thick, 
rigid leaves which are very strongly netted below, the large and 
persistent stipules, and the 3-5 oval segments of the jointed pod. 
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