RUTACEAE RUE FAMILY 
SHRUBBY TREFOIL. HOP TREE 
Ptelea trifoliata L. 
Ptelea is the Greek name of the Elm and is applied 
to this genus because of its similar fruits. 
The Hop Tree is a tall shrub or small tree which is found in 
rocky places from New 
York and Ontario to 
Minnesota and _ south- 
west. It has many local 
names, some of which are 
Wafer Ash, Shrubby 
Trefoil, Swamp Dog- 
wood and Wingseed. Of 
no economic importance, 
it is frequently culti- 
vated as an ornamental 
shrub and its bark was 
formerly much used in 
medicine. 
The small greenish 
white flowers that appear 
in June are usually very 
ill scented, the odor 
resembling that of a 
skunk, but fragrant flowers are occasionally found. Stamens and 
pistils are always present but the stamens in one form (the 
pistillate flowers) aresmall and do not produce pollen, whereas in 
the other form the pistils are dwarfed and functionless. Petals 
and sepals are 3-5 and the number of stamens is the same as the 
number of petals. The pistil consists of a 2-celled ovary, a short 
style and 2 stigmas. The fruit, which matures in August or 
September, is a 2-seeded samara, well adapted to wind dissemi- 
nation. It is very bitter and is sometimes used as a substitute 
for Hops. 
A form of this Hop Tree more common in Illinois is Ptelea 
trifoliata L. var. mollis T. & G. Practically the only difference 
is in its thickish leaflets, which are densely and permanently 
downy on both surfaces. The Lake Michigan shore is probably 
the preferred habitat of this variety in Illinois, and it is known 
in woods from Long Island to Florida and Minnesota to Texas. 
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