Thorns on tree branches or trunks serve as a form of armament. They protect them from large, would-be predators who may want to eat their fruits or flowers. Thorny trees can also serve as effective barriers and create living fences and privacy screens. Pink blooms add colour to the landscape. Pink flowers both brighten shady sites and work as a complementary hue to various shades of green.
Floss Silk Tree
Several varieties of the floss silk tree have thorny trunks and produce pink blooms. The floss silk tree (C. speciosa) grows to 65 feet tall. It prefers full sun to partial shade and tolerates moist to dry soil. Floss silk trees bloom with showy pink, white or burgundy flowers in fall and winter. The "Majestic Beauty" grafted cultivar blooms with pink flowers in fall and winter. This evergreen grows to 50 feet tall with a 55-foot spread and a vase shape. It prefers full sun and tolerates drought and a range of soils.
Most hawthorn trees have thorns, and some bloom with pink flowers. The English hawthorn (C. laevigata), a 25-foot-tall deciduous tree, produces light pink flowers in spring. It has thorny branches and attracts birds with its red fruits. English hawthorns are hardy in USDA zones 4 to 8 and prefer full sun and well-drained soil. The "Double Pink" cultivar produces showy pink flowers.
The toba hawthorn (Crataegus "Toba") also produces pink flowers. It grows to 25 feet tall and has thorny bark. Toba hawthorns prefer full sun and moist to dry soil. They are hardy in zones 4 to 9.
Some coral trees (Erythrina spp.) produce pink flowers and have thorns. The cockspur coral tree (E. crista-galli) grows to 20 feet tall and is hardy in USDA zones 9 to 10. It has thorny, red-brown wood and dark-green, deciduous foliage that turns yellow in fall. Cockspur coral trees bloom with aromatic pink and red flowers from spring through fall. They prefer full sun and moist to dry soil.
The coral tree (E. lysistemon) has thorns and produces toxic seeds. This 35-foot-tall deciduous tree blooms with showy pink and orange flowers. It prefers full sun and tolerates moist to dry soil. Coral trees are hardy in zones 9 to 10.
Other spiny, pink-blooming trees include the desert ironwood (Olneya tesota), which has thorny branches and pink and lavender flowers in summer. It produces long, brown seed pods and has grey-green, evergreen foliage. Desert ironwoods grow to 35 feet tall and are hardy in USDA zones 8 to 10. They prefer full sun and moist to dry soil.
The mimosa tree (Albizia julibrissin) grows to 35 feet tall with a 25-foot spread and has thorny, grey bark. It blooms with puffy, spherical pink flowers in summer, followed by long seed pods. This deciduous tree is hardy in zones 6 to 9 and prefers full sun. It tolerates wind, drought and a range of soils.