The oakleaf poison-ivy usually does not climb as a vine, but occurs as a low-growing shrub. Stems are usually upright in their general growth habit, as they appear in [figure 10]. The shrubs usually have rather slender branches, often covered with a fine pubescence that gives the plant a kind of downy appearance. The leaflets occur in threes, as in other ivy, but are lobed, somewhat on the general plan of the leaves of some kinds of oak. The middle leaflet usually is lobed somewhat alike on both margins and very much resembles a small oak leaf, while the two lateral leaflets are often irregularly lobed. The leaves shown in [figure 11] are a common form. The lighter color on the under side of one of the leaves ([fig. 11, A]) is due to the pubescence, or fine hairs, on the surface. The range in size of leaves varies considerably, even on the same plant; the leaf shown in [figure 11, B], however, is about natural size.
The fruit of oakleaf poison-ivy has the same general appearance as the fruit of common poison-ivy shown in [figure 8], although the individual fruits and stems are often pubescent, while most of the other forms have a waxy, smooth, cream-colored fruit.
Figure 11.—Eastern oakleaf poison-ivy: A, Leaves, showing upper deep green surface and lower lighter colored surface. B, Single leaf, about natural size. The terminal leaflet more nearly resembles an oak leaf than the two lateral leaflets.
Figure 12.—The shaded area is the region where the western poison-oak is likely to occur. Other forms may also be in the same region.