pinnate [ PIN-eyt, -it ] adjective: of a leaf, having two rows of lobes, leaflets, or veins arranged on each side of a common axis resembling a feather
bipinnate [ bahy-PIN-eyt ] adjective: twice pinnate
tripinnate [ trahy-PIN-eyt ] adjective: thrice pinnate
pinnatifid [ pi-NAT–uh-fid ] adjective: of a leaf, pinnately divided, but not all the way down to the central axis
Pinnate is derived from the Latin word pinnatus or feathered. Indeed, in a leaf with pinnate venation the secondary veins are spaced along the central midvein in a feathered pattern. A pinnate leaf can be simple, where the blade is undivided, or compound, divided into leaflets arranged along an axis or rachis like a feather.
Simple leaves with pinnate venation are found on native trees like the beech, birch, black gum, holly, oak, and sassafras pictured below.
Native trees with pinnately compound leaves include black locust, black walnut, hickory, and staghorn sumac pictured below. Some of these native plants have leaves that look similar to the pinnately compound leaves of invasive Ailanthus altissima (tree of heaven, also pictured below), a preferred host of the destructive spotted lanternfly. When plants with similar looking leaves grow in the same area, other diagnostic tools like leaf arrangement, bark, flowers, or fruit may be necessary for identification. Accurate identification is especially important when your goal is to eliminate invasive or other unwanted species to insure that you remove the correct plants.
Ferns have leaves called fronds and leaflets called pinnae. The degrees of fern leaf division vary greatly from species to species.. Fronds can be undivided (simple or entire), lobed (pinnatifid), or divided into separate segments: pinnate (once divided), bipinnate (twice divided), and tripinnate (thrice divided). When some or all of the divisions do not cut to the rachis then pinnatifid is added to the description: pinnate-pinnatifid, bipinnate-pinnatifid, tripinnate-pinnatifid.
Left to right examples of: pinnatifid, pinnate, pinnate-pinnatifid, bipinnate, bipinnate-pinnatifid, and tripinnate-pinnatifid.
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References
Heyer B. Broadleaf Forms & Arrangements. De Anza College.
Jackson D. Tree of Heaven: Native Look-alikes. PennState Extension.
Primitive (seedless) Vascular Plants. Ohio Plants.org (accessed March 2, 2021).
Virginia Tech Dendrology Fact Sheets. Virginia Tech Department. of Forest Resources and Environmental Conservation. (accessed October 19, 2023).