Nature has equipped some flowering trees with thorns, and trimming or pruning them is quite a challenge. Thorns protect the flowers and fruit of these trees from scavenging animals looking for food to eat and enhance security of the container property. While such trees add a decorative element to the garden, take the desired one's mature shape and size into consideration when selecting a planting site so it does not pose a hazard to people or pets. Avoid planting near playgrounds, decks, sidewalks and walkways.
Jerusalem thorn (Parkinsonia aculeata) grows 20 to 25 feet high and features a small trunk with an elegant crown that spreads 20 feet wide. The slim branches are covered with a soft bark and straplike leaves that resemble wispy streamers. Each leaf is comprised of 2 to 4 strips that are 10 to 12 inches long and up to 1-inch wide, and each strip has 25 to 30 pairs of leaflets. Also called Mexican paloverde, the tree bears golden-yellow flowers in spring that add colour and fragrance to the area. The thorny branches pose a danger to passersby if planted near pathways and left untrimmed. The heat- and drought-tolerant tree thrives in USDA hardiness zones 8 to 11.
The hawthorn (Crataegus spp.) forms a nice-sized flowering tree in areas with temperate weather conditions. Many tiny white flowers cover the thorny branches in spring that develop into red berries by the end of summer. Flowers of some species, however, bear an unpleasant odour. English hawthorn (Craetagus laevigata), cockspur hawthorn (Crataegus crusgalli), glossy hawthorn (Crataegus nitidia), thicket hawthorn (Crataegus punctata), Lavalle hawthorn (crataegus x lavallei) and Washington hawthorn (Crataegus phaenophyrum) are commonly grown varieties.
Dwarf Poinciana is not a particular tree but a general name for trees in the genus Caesalpinia. Two commonly grown trees are peachwood and pride of Barbados. The flowers on the trees bloom in the summer to decorate the spot with their reddish-yellow blooms. Thorns are not visible but remain naturally hidden on stems between leaves.
The genus acacia comprises many types of trees and shrubs, with and without thorns. These trees are also called wattles, whistling thorns or thorntrees and depending on the cultivar, produce tiny flowers with five red, white, cream-coloured, purple or yellow petals almost covered by tall stamens. The flowers are naturally arranged in thick clusters on branches with silvery leaves and long, pointed thorns. Trees are commonly sued for ornamental planting and enhance home security when planted along boundary walls or under windows due to the sharp thorns. Parts of the tree are used for medicinal purposes.