Poison Ivy, Oak, and Sumac Information Center


There are a number of terms used on this website in plant identification. This glossary is not comprehensive and gives simple definitions based on term usage on this website. Consult a botanical guide for more complete definitions.
defined leaf

Alternate: leaves are arranged singly along the stem (vine)   alternate

Blade: the expanded, flat portion of a leaf

Compound leaf: a leaf with multiple leaflets (poison ivy, poison oak, and poison sumac have compound leaves)

Opposite: leaves occur in pairs at the stem (vine)   opposite

Palmate: leaflets are arranged at the end of a single point in a fan shape (or like the fingers of a hand). Virginia Creeper leaves are palmate.

Pinnate: leaflets are opposite on the main "stem". In the above picture of a leaf, the outer leaflets are pinnate.

Toothed: the edge of the leaf or leaflet has small projections resembling a saw blade.

Whorled: 3 or more leaves are arranged together at the top of the stem in a circular pattern   whorled