ANACARDIACEAE CASHEW FAMILY 
POISON IVY. POISON OAK 
Rhus Toxicodendron L. 
Poison Ivy or Poison Oak contains a nonvolatile oil 
which if it comes in contact with the skin may produce 
the irritation and blistering that is commonly called 
Ivy poisoning. 
Some persons are 
immune to it and 
others are very 
susceptible; cases 
are known both of 
persons who were 
very susceptible in 
youth but became 
immune or nearly 
so later, and of 
others immune for 
years, who later 
were victims of the 
poisoning. Susceptible persons 
who come in contact with Poison 
Ivy should wash the hands and 
face as soon as possible. Water 
alone will help but strong soap suds 
or solutions of sugar of lead or 
chloride of iron are better. 
The plant is common from Nova 
Scotia to British Columbia and 
south to Florida and Mexico, blooming in June and July. 
It will grow almost anywhere except in low peaty soil. It usu- 
ally grows as a densely fine-hairy vine, climbing by means of 
aerial roots, and will climb trees more than 100 feet tall. Oc- 
casionally it is found growing as an erect shrub. 
The flowers are similar to those of the Smooth Sumach, 
page 184, but they are arranged in a loose panicle, and the 
fruits are white. One must learn to recognize the plant, however, 
by its petioled, trifoliate and more or less downy leaves. The 
leaflets are ovate or round-diamond shape, 1-4 inches long, 
mostly acuminate, entire, finely round toothed or coarsely few 
toothed or lobed, and short soft hairy beneath. 
Poison Sumach or Poison Dogwood, Rhus Vernix L., is our most 
poisonous species. It is common in the swamps of Lake county 
and probably nowhere else in the state. It grows as an upright 
shrub 6-15 feet high and has smooth, pinnate leaves with 7-13 
ovate-oblong, entire leaflets. 
185 
