My tree has compound leaves like an ash, but how do I know what it really is?

Lots of trees have compound leaves (multiple leaflets on one stalk) and get mistaken for ash. With emerald ash borer killing ashes everywhere, correctly telling these apart matters. Here's a field guide to the common look-alikes.

True ash (Fraxinus): - Opposite branching and leaves (key!), 5-9 leaflets - Diamond-pattern ridged bark on mature white/green ash - Single samara seeds (like a canoe paddle)

Common ash look-alikes:

• Boxelder (Acer negundo) — a maple in disguise; opposite leaves but usually only 3-5 leaflets, irregularly toothed; produces paired maple-style samaras
• Black walnut (Juglans nigra) — alternate, 15-23 leaflets, aromatic when crushed, round green husked nuts, chambered pith in twigs
• Hickory (Carya) — alternate, 5-9 leaflets, larger terminal leaflets, hard nuts
• Tree-of-heaven (Ailanthus) — alternate, many leaflets with a distinctive notched gland at the base; crushed leaves smell rank (peanut/rotten)
• Black locust (Robinia) — alternate, oval leaflets, thorns at leaf bases, bean-like pods
• Mountain ash (Sorbus) — not a true ash; alternate leaves, clusters of orange-red berries

The fastest first test: Check branching arrangement. Opposite narrows it to ash, boxelder, and a few others; alternate rules ash out entirely. (Remember "MAD Cap Horse" for opposite trees: Maple, Ash, Dogwood, etc.)

Try our interactive Tree ID Guide or browse the Plant Database for photos.