The list of plants with thorns suitable for landscaping purposes is extensive and includes broadleaved evergreens, perennials, deciduous shrubs and trees. These species include many types non-native to North America but adapted to some of the U.S. Department of Agriculture plant hardiness zones. Consider the presence of thorns before using some of these plants in areas where people have opportunity to encounter them in their daily travels, as advised by the Missouri Botanical Garden.
Hawthorn trees have reputations for possessing sharp thorns on their branches; species such as Ontario hawthorn feature horizontal limbs armed with 2-inch spines. Pruning these trees becomes difficult due to the thorns, but hawthorns offer spring flowers and excellent fall colour as a rule, making them worth the effort. Other trees with thorns include the honey locust, Osage orange and the wild plum -- all native types. Non-native thorny species include the common jujube tree and the harigiri, a tree growing between 40 and 60 feet, used as a shade or specimen tree, but with thorns on its trunk when immature.
Mountain thistle, a shrubby perennial plant, grows in zones 7 through 10. Its leaves have spines and its flowers, resembling those of snapdragons, are pinkish red. Mountain thistle grows in many soil types but not in waterlogged areas. Thorns are present on perennials such as the globe thistle, prickly pear and sea holly. Sea holly has spiny flowers shaped like eggs; they are purple-blue and bloom all summer. The asparagus fern is not a true fern but this perennial has evergreen foliage and small thorns.
One aspect of the numerous varieties of deciduous shrub roses available for landscaping is their spines, but these plants come in many sizes, making them versatile. The Lutea cultivar of the banksia rose, for example, grows to 20 feet high, while the Chewground type of shrub rose can be 12 inches tall. Other deciduous shrubs with thorns include raspberry bushes, hardy orange, Japanese barberry, Chickasaw plum, Chinese matrimony vine and the scarlet firethorn. The hardy orange has extensive, sharp thorns, making it fit as a barrier plant or hedge in zones 5 through 9.
Annuals such as the spider flower of South America and the prickly poppy from the western United States have thorns. Some vines, including bougainvillea and sarsaparilla plant, have thorns, as well. Bougainvillea has its thorns along the stems where the leaves grow out. These vines are suitable only for zones 9 through 11 if kept outside, but they work as greenhouse or sun room plants in colder areas. Broadleaved evergreen species such as the pigeon berry and citrus lemon are other thorny plants landscapers value for their foliage, flowers and fruiting ability.
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