Pruning and Shaping Hedges
Once planted, your hedge will need good care if it is to thrive. Most importantly, keep young plants watered for the first few years during dry spells until the hedge has become established. It should then not need additional watering except in dry periods in the summer. Fertilize all hedges in spring with a balanced fertilizer, such as blood, fish, and bone. At the same time, regularly clear any weeds from the base of the hedge, and after rain, or when the soil is moist, top off any mulch. Clipping and shaping How you shape your hedges will depend on their age and whether you have grown them to be formal or informal.
- Young informal hedges need no shaping, although shortening any long, whippy shoots will encourage them to bush out.
- Young formal hedges may be pruned to shape and direct growth. Evergreens need only their sideshoots lightly trimmed for a few years after planting. Leave the main upright, or leading, shoot(s) to grow to the final hedge height. Deciduous hedges that are to have a dense, formal shape require more early shaping. In general, cut back the main shoot and any strong sideshoots by one-third after planting; repeat the following winter. Prune vigorous privet and hawthorn harder: cut back to within 12 in (30 cm) of soil level in late spring. In late summer, shorten sideshoots; then, in winter, cut the previous season’s growth back by half.
- Mature informal hedges should be merely trimmed in spring or summer, and left unpruned unless they are outgrowing their space or looking particularly untidy. Snip off any too-long shoots and keep the height under control.
- Mature formal hedges need keeping in shape with regular clipping. This keeps growth dense, and the hedge thick and lush from top to toe. It also prevents it from expanding over the years. How often you clip depends on the plants and their rate of growth, but all hedges need at least one cut a year. For deciduous hedges and small-leaved evergreens, use garden shears or a powered hedge trimmer, keeping the blades parallel to the hedge at all times for flat sides. For large-leaved evergreens, such as cherry laurel (Prunus laurocerasus) and tough-leaved holly, use pruners to cut back individual shoots.
Filling in Gaps in a Hedge
If a plant in a young hedge dies, dig it out and plant a new one. Switch some of the soil with some from another part of the garden as a precaution, enriching it with well-rotted compost or manure. In an established hedge, remove the dead plant, and fill the gap with shoots of adjacent plants trained horizontally along strings or wires set between canes.
If a stem is forced out of position by snow or wind, tie it back in place using soft twine. Clipping your hedge into an A-shape will reduce the risk of this happening. Cut out browning foliage, particularly on conifers, as it will not green up. If it leaves a gap, tie adjacent branches together with soft twine. Keep an eye out for more dead patches, which may indicate disease.
Renovating an Overgrown Hedge
Where an established hedge is overgrown, start by cutting back weeds such as ivy and brambles. When new growth sprouts, paint the leaves with glyphosate weedkiller—more than once if needed. Remove any dead wood and cut the hedge back. Apart from when dealing with conifers, spread this over two years—cut back the top and one side one year, and the other side the next.
Beech, hornbeam, and hawthorn can be cut back hard in late winter before new leaves appear. If regrowth is poor in the first season, delay the second half of the job for another year. For an old forsythia hedge, cut out some of the old wood once flowering is over. Among evergreens, yew, box, cherry laurel, privet, lonicera, holly, escallonia, evergreen berberis, and pyracantha can cope with hard pruning, in mid- to late spring when growth is well under way. After pruning, fertilize and water, and mulch with bulky organic matter. Make a trim line by tying string to two canes; insert them at each end of your hedge to make a clipping guide for formal hedges, such as boxwood.
Clipping Hedges into a Shape
Clipping hedges into shape Prune formal hedges, such as beech and yew, from the time of planting so that the plants form a wedge or A-shape as they grow. These shapes allow light to reach all areas of the hedge, which will encourage even growth.
If you live in an area that experiences snow, clip the top into a point or narrow A-shape so that the snow cannot settle on the top where its weight may damage the top of the hedge.
For a hedge with a narrow profile, clip the sides regularly from the start. Trim it back each time to the last cut, for a smooth finish. Beech with a pointed top to shed snow.