Keep unwanted visitors--both people and browsing animals--out of your garden with thorn-bush trees, that is shrubs that grow tall and have thorns. Create a formal uniform hedge with individual thorny shrubs, or create a rambling work of art by mixing deciduous flowering shrubs and glossy broad-leaf evergreens. After you completed the work of the intensive planning and planting, your thorny hedge should grow well with minimum maintenance. It can also make a safe nesting spot for birds.
Evaluate the Planting Site
Evaluate the area you want to fence with a thorny hedge before you plant or even pick out shrubs to use. Consider the sun exposure, soil and access to water. When picking shrubs for your hedge, match them as closely as possible with the environment. Avoid planting shrubs that need moist soil in a dry area away from easy water access or a sun-loving variety in a shady area. Consider safety factors. Thorny shrubs can pose a serious risk in child and pet play areas.
Create a Dense Hedge
Dig a trench about 12 inches deep the length of the fence line. For a dense hedge, dig a second trench 18 inches away. A single row of thorny shrubs can leave gaps at the base, but with a double row, the base is more difficult to penetrate. Space shrubs 18 to 30 inches apart in a row. If you are planting small shrubs, growing 3 feet tall or less, space them 6 to 8 inches apart.
Getting Shrubs in the Ground
Wearing gloves and eye protection, take the shrubs out of the nursery containers and set them in the trench. Build up or remove soil under each one so that the base of the stem is level with the edge of the trench. When planting a double row, stagger the shrubs to create a triangle between the plants. Replace the soil around the newly transplanted shrubs and then water each plant. Plant thorny shrubs in the fall or early winter during the rainy season.
Ongoing Care and Maintenance
While specific care varies depending on the types of shrubs you grow, some general guidelines apply. Prune to maintain a formal shape in summer unless you are growing flowering shrubs. Prune flowering shrubs in winter. If you enjoy a natural look, do minimal pruning to control basic shape and size. Formal hedges should be sheared in the summer. Remember to sanitize your tools after pruning using equal parts clean water and rubbing alcohol. Except in cases of extremely poor soil, thorny hedges don't require regular fertilizer to thrive. Water requirements vary by plant type.
Some Thorny Deciduous Shrubs
Thorny deciduous shrubs shed their leaves in winter leaving the bare branches exposed, but they are still very much a deterrent year-round. Bougainvillea (Bougainvillea spp.), hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11 creates a dense thicket with 2-inch-long thorns showy flowers Shrubby rose bushes like the nearly wild rose (Rosa x "Nearly Wild") give a cottage garden charm to a thorny fence. It grows in USDA zones 3 through 9 and gets about 3 feet tall, ideal for a low barrier.
Types of Thorny Evergreen Shrubs
Broadleaf evergreens keep their glossy leaves year-round. One evergreen shrub that makes a good, thorny fence in some Mediterranean climate zones is the 3 to 6-foot-tall crown of thorns (Euphorbia milii). It grows in USDA zones 9 through 11 and makes a formidable barrier with it's 1/2-inch-long thorns. Bright red flowers bloom periodically through the season. American holly (Ilex opaca), hardy in USDA zones 5 through 9, can also grow in some Mediterranean climate zones. It grows a dense evergreen barrier, and in winter has bright red berries. It grows 15 to 30 feet tall but will remain smaller with regular pruning.
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