Gardening on an Exposed Site
DK - Learn to Garden , 2008 Dorling Kindersley Limited
Gardens that are located at the top of a hill are very exposed to weather conditions, especially drying and high winds. Choose plants that are tolerant to those special conditions.
Like humans, plants are predominantly composed of water. This makes them prone to dehydration—a constant threat in an exposed garden, whether by the coast, inland, or at high altitude. Wind can test plants to the limit, and only those species that are adapted to resist its drying effects—either by storing water in their leaves or roots, or reducing the loss of water through their leaves—stand a chance. On the positive side, exposed gardens usually have high light levels and excellent air circulation, reducing fungal disease. But strong sun can also fade subtle flower colors, and good air circulation can quickly turn into an eddying wind that damages plants.
Wind Damage and Stunting
Exposure causes slow, stunted growth—a tree in an exposed garden can be as little as half the size of one of the same age and species in a sheltered garden. Trees and shrubs can also be “pruned” by the prevailing wind. In an exposed inland garden, very cold winds are usually the main enemy. If you garden on the coast, you should benefit from a mainly frost-free climate because sea temperatures rarely drop below freezing, and thus keep the winds coming over them warm. On the down side, salt spray borne on the breeze can “fry” leaves and often kills plants as effectively as frost.
Using Plants for Shelter
Minimize the effects of wind by using a shelter belt of plants. Unlike solid walls and fences, which can cause wind to accelerate and eddy through a garden, plants slow it down gently. A shelter belt can be anything from a hedge to a dense planting of trees and shrubs. One of the best hedging plants for seaside gardens is salt-tolerant Griselinia littoralis, while hornbeam (Carpinus betulus) makes a good, dense hedge for exposed inland gardens. You can also use synthetic windbreak materials. These usually take the form of a closely woven fabric mesh, which can be attached to regularly spaced posts. A double layer will provide greater protection. A windbreak like this will slow the wind considerably over a short distance. The mesh can be removed as soon as the plants are settled—between three and five years. Individual plants can be cosseted in a similar way with a “cage” of mesh netting on posts, and trees or shrubs planted as small “whips” (usually one to two years old) can be given a head start if surrounded by a biodegradable plastic guard to create a warm and sheltered microclimate.
Plants for Exposed Gardens
Successful seaside gardens often take a cue from nature by using native plants that proliferate on the shoreline. These can provide a backdrop for more exotic ornamentals. Alternatively, provide shelter for plants that don’t cope so well with exposure to the elements. Thick wind-reducing plantings on the boundaries of the garden, and a series of “garden rooms” surrounded by more hedges within, create very sheltered areas. In a mild coastal climate, this will enable you to grow tender, exotic plants.
The Royal Horticultural Society garden at Hyde Hall is an example of an exposed inland garden, perched on top of a hill among the rolling, arable landscape of mid-Essex, England. Throughout summer, the prevailing wind is a hot, dry southwesterly that can desiccate plants in no time, while in winter a cold northeasterly can cause significant wind chill. Despite this, the garden is bursting with plants, the majority of which have been selected because of their tolerance to exposure.