A shrub is distinguished from a tree by its multiple stems and shorter height. A hedge or hedgerow is a line of closely spaced shrubs and tree species, planted and trained in such a way as to form a barrier or to mark the boundary of an area. Hedges used to separate a road from adjoining fields or one field from another, and of sufficient age to incorporate larger trees, are known as hedgerows. It is also a simple form of topiary. Shrubs and hedges usually grow between 5–20 ft tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience.
An area of cultivated shrubs in a park or garden is known as a shrubbery. When clipped as topiary, shrubs and hedges generally have dense foliage and many small leafy branches growing close together. Many shrubs and hedges respond well to renewal pruning, in which hard cutting back to a ‘stool’ results in long new stems known as ‘canes’. Other shrubs and hedges respond better to selective pruning to reveal their structure and character. Shrubs and hedges found in common gardens are generally broad-leaved plants, though some smaller conifers such as Mountain Pine and Common Juniper are also shrubby in structure. Shrubs and hedges can be either deciduous or evergreen.
Seasonal information: Shrubs and hedges usually grow between 15 and 20 feet tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience but usually do well all year round.
Location: As with any plant life, the key to success is to provide the conditions which your shrub or hedge most desires. To be sure, you will need to research the exact species of plant for details, but as a rule of thumb: shrubs and hedges should be planted at least six weeks before winter in a partially lit area.
Planting instructions: Any hedge plant will need the same soil, water, and light conditions as it would if it were planted as a single specimen. When purchasing plants, check the tag for growing requirements and make sure your site is right for them. It is one thing to lose a plant placed in the wrong spot, but losing an entire hedge can be expensive. For a faster-growing hedge, buy 5-gallon plants as close to the height you want. Look for full plants, but expect a few bare spots at first. When a plant is continually sheared from the top, the lower areas will fill in. Check the width of the mature plant and space the plants according to that measurement.
Watering: Water the shrub thoroughly prior to planting. This step is the most important for reducing transplanting stress. Place the shrub or hedge at the proper depth in the planting hole. Always keep the base of the trunk or stem above ground. Build a soil berm around the shrub. A berm is a shallow basin formed by mounding soil from the planting hole around the drip line. The berm should be two to four inches high. Fill the berm with water, let it drain and then fill it again. The double watering will ensure that water reaches the bottom of the planting hole. Keep the berm in place for the first growing season, then knock it down when seasonal rains begin.
Fertilization: Generally, you should fertilize your shrubs in either the spring or fall. This recommendation applies only if the condition of your shrub indicates it need fertilization. The extension does not advise an annual fertilization based on the calendar only. Set out any spring application before the start of new growth. Apply in autumn after the first frost. Avoid late summer applications, which may promote new growth that won’t survive the winter. New shrubs typically need fertilization to help them become established. If you place new plants in the ground in autumn, wait until spring to fertilize. If you set new plants in the soil in spring, wait six to eight weeks before applying a fertilizer. A slow-release fertilizer gives the best results for new plants. Give only a light application of fertilizer for your new shrubs.
Weed Control: Beyond mechanical weed removal methods, selective herbicides are usually the safest method of removing unwanted grass and weeds around shrubs and trees. Applying a granular fertilizer will supply a steady stream of herbicide into the soil as the materials gradually dissolve. Stubborn, large weeds may require a direct application of non-selective herbicide to halt their growth. Hand-held sprayers allow you to focus the herbicide directly onto the weedy growth, minimizing damage to surrounding plants.
Pests and Disease: Due to the variation of shrubs and hedges, there are many common pests and ailments which plague them such as aphids, leaf-hoppers, or the gypsy moth. Many of these pests are common garden critters and with regular care and attention can be treated early to prevent long-term damage to your shrubs and hedges. Monitor leaves for signs of spotting or nesting. The soil area around the base of the shrub or hedge should be kept weed free and allow you to view the base clearly; if you have any concerns, you should contact a botanist.
Pruning: An area of cultivated shrubs in a park or garden is known as a shrubbery. When clipped as topiary, shrubs and hedges generally have dense foliage and many small leafy branches growing close together. Many shrubs and hedges respond well to renewal pruning, in which hard cutting back to a “stool” results in long new stems known as “canes.” Other shrubs and hedges respond better to selective pruning to reveal their structure and character.
Trimming a shrub or hedge helps to promote bushy growth. If a flail cutter is used, then the flail must be kept sharp to ensure that the cutting is effective on the shrub or hedge. The disadvantage of this is that the shrub or hedge species takes a number of years before it will flower again and subsequently bear fruit for wildlife and people. If the shrub or hedge is trimmed repeatedly at the same height, a “hard knuckle” will start to form at that height – similar to the shape of a Pollard tree.
Pollination: Flowering seasons occurs anytime between late spring and early autumn. Fruits develop immediately afterward, ripening and persisting into fall and winter months until eaten and distributed by wildlife or by naturally dropping off. Seeds sprout in fall or spring when conditions are favorable.