APRIL – Divide and connect

Hedges are a stalwart of garden design – Catherine Thomas explores the versatility of these structural plants.

The garden of rooms is something of a cliché these days but it is an apt description of the sense of enclosure most of us enjoy in our gardens. This is where garden design most closely resembles architecture. Where an architect works with hard materials, a garden designer, as often as not, works with living plants to create enclosed spaces. Like rooms in a house these will be used for different purposes and possess different characteristics and ambience.

Some will be inward looking, furnished with plants; some will be outward looking with a wonderful view. Others will be designed such that you feel invited to move from room to room. As you wander from one room to another the garden will almost certainly feel larger than it is in reality. Both professionals – architects and garden designers – are involved with defining spaces and creating links between them. Of course, I design walls, fences and steps, too, but it is a real pleasure to design with living plants. My hope is that they will grow over the years, some even for centuries, developing organically long after I and my clients have been forgotten.

I am speaking of hedges: the structural plants which can give a garden its definition and form. Whether formal or informal, evergreen or deciduous, a hedge can provide the subdividing walls of our gardens. Sometimes we need them to screen a road or provide privacy from the neighbours but there is so much more they can offer.

Flexible shapes

It is easier in garden design than in architecture to make curves: rooms can be round and curvy. The hedge top may be sculpted into waves, balls or castellations. A turret may be there this year but you can transform it into a bird next year. The plant will grow obligingly to accommodate your whim. I’ve used hedges like the wings of a theatre, creating sheltered pockets of privacy whilst keeping the main view open. Buttresses can be planted to divide a long herbaceous border with rhythmic interventions.

Hedge choices

Hedges may be of closely clipped evergreens, such as yew or box, or loose and informal like roses. The feeling in the enclosed space will be completely different depending on which you choose. For a formal look, choose evergreens with small leaves or needles, ideally dark in colour. Yew has almost black needles with a matt, non-reflective quality which tends to recede visually. It makes a fabulous backdrop to light coloured plants or sculpture in front of it.
By contrast, the bright, shiny green leaves of laurel tend to advance visually and steal the show from whatever is planted in front. In fact, like rhododendrons, it practises “allelopathy”, producing biochemicals to inhibit the growth of plants around it to give it a competitive edge. The notorious x Cupressocyparis leylandii must be used with care but, provided it is regularly trimmed, it makes a fine formal hedge though it is shorter lived than the more handsome yew. These evergreen hedges provide permanent structure throughout the seasons, whilst showier plants perform dramatically, then “rest” like unemployed actors.

Some flowering plants make lovely fragrant hedges with a soft, informal effect. Rosa rugosa has disease-free, fresh green leaves and heavily scented pink or white flowers throughout the summer. In the autumn, the leaves turn butter yellow, lit up by hips the size of cherry tomatoes. Osmanthus delavayii or O. burkwoodii can give you the best of both worlds with small dark evergreen leaves and scented jasminelike flowers.

Tall grasses can make a more ephemeral division of space. Miscanthus will grow to over six feet and makes a dense screen from midsummer through to February when the season’s growth should be cut down. I’ve used a sinuous trail of Calamagrostis “Karl Forster” to separate a lively blue and orange planting scheme from harmonious pastels.

Pleached or ‘stilt’ hedges are trees grown bare stemmed to a height up to about six or seven feet, then branches are trained horizontally and tightly pruned. After two or three years of training and pruning you will have a dense hedge elevated above the ground on “stilts”. The effect is airy and the view beyond can be tantalisingly glimpsed between the trunks. The play of light and shadow when the sun is low adds another dimension to your garden. The tree trunks as they age become a sculptural colonnade. Hornbeam and lime trees were traditionally used, but flowering and fruiting trees can also be used – I’ve planted the crab apple, Malus transitoria very effectively. Wildlife shelters

Hedges are great for wildlife, too. Animals will live in and on your hedges, raising their young in their shelter and nourished by their fruits and leaves. Insects will spread pollen to the plant’s kith and kin in surrounding gardens. Hedges provide wildlife corridors, allowing endangered creatures like hedgehogs to travel safely to find a mate and forage for food. Toads will live in the cool leaf litter beneath them. Both hedgehogs and toads love slugs and will help you look after your garden if you look after them. Planting a hedge is an investment that will richly reward you – it is truly an investment that will grow.