The Jerusalem thorn, also known as Parkinsonia aculeate, the jellybean tree and the Mexican Palo Verde, is a small tree native to the southwestern United States and Mexico. It is named for the long spines covering its thin branches. Widely used in landscaping and gardening, this plant is popular in warm climates and can be grown as a tree or a shrub.
A relative of the pea, the Jerusalem thorn is a fast growing tree, able to reach up to 25 feet (about 7.5 m) tall. Its thin, weeping branches can sprawl out to a similar width. Branches are covered in thorns each up to 1 inch (2.5 cm) long. Young twigs and branches remain bright green for years before the bark thickens and grays.
The distinctive leaves of the Jerusalem thorn are formed by as many as 20 pairs of oval leaflets growing from long midribs that resemble large feathers. The deciduous leaves spread open immediately after rainfall and fall away in dryer weather. Leaflets fall first, leaving the streamer-midribs behind before these too dry and fall. Even without its leaves, the Jerusalem thorn can continue to photosynthesize through its bright green branches.
In springtime, the tree blossoms, producing a dense covering of fragrant flowers. Each flower is about an inch (2.5 cm) in diameter, with five bright yellow petals. Flowers produce brown, leathery bean pods.
Native to the deserts of North America, the Jerusalem thorn thrives in warm, arid climates. In regions where leafy green plants are scarce, this tree does well, and it is able to survive in areas that receive less than 12 inches (30 cm) of rain per year. It does not, however, tolerate wet conditions well, and it cannot survive the freezing temperatures of northern winters.
With its irregular-shaped canopy, the Jerusalem thorn is better suited to informal yards than heavily manicured gardens. Some people allow it to spread as a low tree, and others prefer to trim it back as a shrub. It is widely used in commercial and municipal landscaping to line streets and parking lots throughout the southwestern U.S. and in other hot, arid regions around the world, providing greenery in areas where irrigation is impractical.
Since becoming popular as a cultivated tree, the Jerusalem thorn has spread to other regions. The tree also grows wild in Florida, California, Central America, South America, the Caribbean region and the West Indies. In Australia’s Northern Territory, the Jerusalem thorn is highly invasive and regarded as a weed and a nuisance.