Parkinsonia aculeata aka Palo Verde

Parkinsonia aculeata is a small, thorny tree in the pea family. Gardeners call it Jerusalem thorn, retama, or Mexican palo verde. Kew places its native range from Mexico to northern Argentina, including the Caribbean. Other sources include the southwestern United States in its range. It grows in dry valleys and desert grasslands. Garden trees reach about 15–25 feet (4.6–7.6 metres) tall. Their spread reaches 20–25 feet (6.1–7.6 metres). Some accounts report heights of 40 feet (12.2 metres).

The tree grows fast and often forms several low trunks. Its open crown spreads wide, with branch tips that droop. Older trees may grow wider than they grow tall. Young bark is smooth and green or yellow-green. With age, it turns brown or grey and becomes scaly. Sharp spines grow at the leaf bases. The compound leaves carry many tiny green leaflets. These fall before the long, curved leaf stalks. Sources describe the tree as both deciduous and evergreen. Its foliage gives light shade, with no striking autumn colour.

Yellow flowers appear in spring and may last into summer. They have five petals, with red on the largest petal. Loose, hanging racemes carry the blooms, which have a faint scent. Bees visit the flowers. The fruit is a dry, pointed pod. Each pod narrows between its seeds, giving it a beaded outline. Pods turn brown as they ripen in late summer. They add interest but do not create much litter.

Grow this tree in full sun and well-drained soil. It accepts sand, loam, and clay that drains well. It also tolerates acidic and alkaline soil, heat, drought, and salt spray. UF/IFAS lists USDA zones 8b–11. Young growth can suffer frost damage near 30°F (−1°C). Wet soil can cause root rot despite reports of seasonal flood tolerance. Pruning helps build a strong branch structure. Keep its spines away from paths and protect its thin bark. Scale insects, thorn bugs, and witches’ broom may occur. Serious pest problems are uncommon, but trees may live only 15–20 years.

People plant it for flowers, light shade, hedges, and soil stabilisation. Its hard wood serves for posts, carpentry, fuel, and charcoal. UF/IFAS classes it as invasive in Florida and advises against planting. Seeds have food uses, raw or cooked, but contain antinutritional compounds. Cooking improves their digestibility. Leaves contain reported toxic hydrocyanic acid. Traditional remedies use several parts, but reports also describe abortion-inducing effects.