How to Select Climbers and Wall Shrubs for your Garden
Garden walls present the best opportunities for growing climbers and shrubs that benefit from the support and protection offered, whether it be from the cold, the wind or the sun. Trellis, screens, pergolas, arcades, arbours and summer houses also provide good support for climbers and have an immediate impact on the garden while introducing a valuable vertical element.
Certain plants are better suited to specific structures according to their vigour and means of attachment. Reasonably vigorous twining climbers that provide adequate cover without swamping the structure are suited to pergolas and arbours. Either a single species, such as wisteria, can be used to create a spectacular display at one time of the year or a collection of plants, including Clematis armandii and Vitis vinifera ‘Purpurea’, can be used to provide a succession of flowering and foliage interest.
Slow-growing scramblers, such as roses and Jasmi-num nudiflorum, that require careful tying in because they do not actually attach themselves to the structure, work well on small trellis screens; while self-clinging climbers such as ivies, Schizophragma and Hydrangea petiolaris, are best suited to walls which provide a suitable surface for their aerial roots or suckers to adhere to. The habit of a plant may also make it suitable for growing against a wall. Kerria japonica, Pyracantha coccinea, Chaenomeles species,
Forsythia suspensa and Robinia hispida all have fairly stiff, upright stems that grow close to the wall and can be pruned and trained to fill the available space.
Climbers that hook their stems onto the support with the help of coiling tendrils need wires to wrap themselves around, or alternatively are well adapted to threading their way through other plants as they do in their wild state. When choosing a host plant the climber’s vigour should be taken into account.
Many other factors will govern the choice of plants. The style of the garden dictates whether the plants should be slow-growing and neatly tied in to give a controlled form or whether they should be given a fairly free rein to grow at will. For example, the relaxed effect that is achieved by allowing honeysuckle to cascade over a structure with its scent mingling with that of other vigorous climbers, such as rambling roses and summer jasmine, is perfect for a cottage, romantic or wild garden. In contrast, a strictly pruned and flat-trained Magnolia grandiflora with its large, smooth, architectural leaves and single, stiff, waxy-white summer flowers, would be a fitting focal point in an enclosed courtyard.
It may be that a fast-growing climber is required to camouflage an ugly building or cover a trellis screen placed in front of an eyesore: Persicaria aubertii (the mile-a-minute or Russian vine), Parthenocissus quin-quefolia, Virginia creeper and the related P. tricuspidata (the Boston ivy), Vitis coignetiae (the crimson glory vine), Celastrus orbiculatus (the Oriental bittersweet), Akebia quinata and Clematis montana are all suitable for this purpose. However, these plants need a lot of space and require constant pruning or have to be replaced in order to prevent them from swamping all other nearby plants, lifting tiles or blocking gutters. Their speed of growth, which can be their greatest asset, has also earned them a bad reputation.
In fact most climbers are fast growers which need pruning and tying in to keep them under control. Some need near constant attention, others can be attended to once a year, either in the winter or in early spring or after flowering, depending on the requirements of the plant. It is always advisable to ensure that the structure is sound before the plant starts to cover it and that it is large enough to accommodate the plant when mature.
The aspect of the wall is an important consideration when choosing suitable plants to clothe it. A protected wall that receives the sun for most of the day is likely to be several degrees warmer than one that receives little direct sunlight. Marginally hardy plants can survive when grown against such south-facing, warm walls. For example, in areas where Clematis montana is perfectly hardy, C. armandii will require a southern aspect. Many Californian and Central American species such as the attractive Ceanothus and Fremontodendron ccdifornicum will flourish in temperate climates when grown against a wall. Magnolia grandiflora makes a large freestanding tree in Mediterranean climates but will also survive and flower in areas where the summer rainfall is higher and season shorter when placed against a wall. The way in which a wall absorbs and then releases heat produces not only additional winter warmth and hotter summers but also extends the season, allowing the wood to ripen well and survive the winter cold.
In contrast, there are many plants that prefer shady situations – including Jasminum nudiflorum, Kerria japonica, Garrya elliptica, Berberidopsis corallina and Lapageria rosea – but this does not necessarily mean that they are frost-hardy; many shade-loving climbers are still tender. There are also a number of plants that tolerate the poorest conditions and are able to clothe seemingly inhospitable walls. These include ivies as well as the climbing Euonymus radicans, Parthenocis-sus species and Hydrangea petiolaris.
Camellias, winter sweet {Chimonanthus praecox) and Jasminum nudiflorum which blossom early in spring, when there is still a risk of frost, benefit from growing against a wall that does not receive direct morning sun, because this would defrost the blooms too quickly and damage them.
A notable way of extending the season of certain plants and adding a new dimension to a design is to grow climbers through other plants. The most vigorous climbers such as Vitis coignetiae, Celastrus orbiculatus and Wisteria sinensis are successful only in tall trees, but there are a number of other species that grow happily through shrubs without swamping them. Clematis are the most frequently used in this instance. Herbaceous climbers such as Codmwpsis convolvulacea, Tropaeolum speciosum and Lathyrus grandiflorus are also well suited.
