Zanthoxylum americanum aka Northern Prickly Ash

Zanthoxylum americanum has two names: prickly ash and toothache tree. It belongs to the citrus family, not the ash family. Its native range covers southeast Canada and central and eastern America. It also grows in northeast Mexico, in Nuevo León and Tamaulipas. It grows in woods, thickets, rocky slopes, and moist ravines. This shrub or small tree sheds its leaves each year. It spreads through root suckers, shoots that grow from roots.

Wild shrubs often stand 8–10 feet (2.4–3 metres) tall. Garden plants can reach 20 feet (6.1 metres). Their spread can reach 15 feet (4.57 metres). Some trees reach 25 feet (7.6 metres). Several stems can grow together and form dense thickets. Young bark is smooth and grey-brown. Grooves form in the bark as it ages. Thick green twigs turn grey-brown and bear sharp spines in pairs. Broken twigs and crushed leaves give off a citrus scent. The leaves grow in turn along the stem, not in pairs. Each pinnate leaf has five to eleven leaflets along a central stalk. The leaflets have toothed edges. Their tops shine green, while their lower sides are paler.

Small flowers with a scent bloom before the leaves in early spring. Missouri Botanical Garden gives April as the month of bloom. The flowers are yellow-green and grow in small groups. Male and female flowers grow on separate plants. The blooms give little show, but the fruit adds interest. Small red fruits grow in groups and split when ripe. They show glossy seeds, which range from red-brown to black. Birds and butterflies visit this plant. Giant swallowtail caterpillars eat its leaves.

Grow prickly ash in sun or part shade. Oregon State University says it can cope with shade, too. Average soil suits it, with good drainage and moderate moisture. It can cope with poor soil and drought. It also grows near black walnut trees. Its listed USDA hardiness range is zones 3–7. Root suckers can form a dense screen or thorny barrier. It suits hedges, woods, and gardens of native plants. Reports list no major pest or disease problems. In some years, swallowtail caterpillars may strip many leaves.

People have used cooked seeds as a pepper-like spice. They have also used bark and fruit for toothache. Past uses include relief from rheumatic pain. These uses do not prove that home remedies are safe. Reports warn of less iron uptake. They also warn that it may stimulate the nervous system. Too much may affect medicines that prevent blood clotting.