Boxelder, Acer negundo L.
DISTINGUISHING CHARACTERISTICS: Leaves once-pinnately compound, opposite; leaflets 3 to 9 in number (usually 3 or 5), ovate, sometimes shallowly lobed, 2 to 4 inches long, the margins entire or coarsely and shallowly toothed. Winter twigs moderate in diameter, green or purple, usually coated with a white waxy substance; leaf scars V-shaped with 3 bundle scars, opposing leaf scars joined at their ends and thus encircling the twigs, the junction prolonged upward into a short point on each side of the twig. Buds ovoid, densely white-hairy, 1/8 to 1/4 inch long with 2 or 4 visible scales. Flowers very small, greenish, dioecious, apetalous, appearing just before the leaves in spring; staminate long-stalked in umbellike clusters; pistillate in racemes. Fruit a pair of samaras joined at the base; wings 1 to 2 inches long, drooping; samaras ripening in autumn, often remaining on the tree through winter. Bark gray or brown, furrowed with scaly ridges.
SIMILAR TREES: Ashes, the only other common trees with opposite, pinnately compound leaves, have 7 to 11 leaflets and single, paddle-shaped samaras. Easily distinguished from other maples and ashes in winter by its greenish or purple twigs, white-hairy buds, and upward-poiting leaf scar junctions.
IOWA DISTRIBUTION: Native throughout the state, occasionally cultivated.
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