Living Windbreaks for Protecting Vegetables
Shelter and Prosper
While it is obvious that vegetables need water, the necessity foris far less obvious. Yet research has shown that if vegetables such as brassicas, carrots, tomatoes, lettuces, runner beans and , among others, are sheltered from even light summer breezes yields will be between 20 and 30% higher. These are higher increases than are usually obtained with irrigation or extra fertilizers.
Winds are both directly and indirectly detrimental to plant growth. The adverse effects of strong winds are obvious, buffeting plants like Brussels sprouts and other brassicas so that their root systems are loosened, tearing the foliage of climbing and dwarf, impairing the quality of salad plants. Salt-laden coastal winds, extremely cold winds, and occasionally very warm winds are also harmful.
Even gentle winds have a desiccating effect, both on plants, so increasing transpiration, and on the, increasing evaporation. With spring-sown seedbeds a combination of low temperatures and high winds drying out the surface can result in very poor germination. In some parts of the country, soil ‘blow’ is a problem which can be alleviated by shelter.
Where sheltered conditions are created soil warms up faster, and many vegetables mature appreciably earlier if sheltered. Shelter also gives some protection against hail and driving rain, both of which destroyand even vegetables in more mature stages. Perhaps most important of all, pollinating and other beneficial insects are encouraged.
The purpose of any windbreak is simply to reduce the speed of the wind. The choice lies between living and artificial materials — trees, hedges, and tall wind-resistant plants on the one hand, and fences and netting on the other. Whatever is chosen it should be about 50 per cent permeable, so that the wind is filtered through it: otherwise damaging turbulence is created. It should also be as extensive as possible, for wind has a knack of nipping around the end of short barriers and attacking with still greater intensity.
As living windbreaks compete for nutrients, water and light, artificial windbreaks are more practical in the average smallish vegetable garden. Lath-and-wattle fences, bamboo-cane screens, hessian and coir netting (hop lewing), and the many plastic-net windbreak materials can all be used. A windbreak 150-180cm (5-6ft) high around the perimeter of the garden is invaluable. Alternatively, strips of netting or even hessian sacking, anything from 30-90cm (1-3ft) high depending on the crop, can be strung between rows, or beds, of vegetables. Windbreak netting is usually battened to posts, but make sure it is put up securely, reinforcing corner posts if necessary. They take tremendous strain when a strong wind is blowing, the nets billowing like sails.
Living windbreaks that are justified in a vegetable garden are vegetable themselves: Jerusalem artichokes andare the two most appropriate. Jerusalem artichokes are among the most rugged of vegetables, and planted 30cm (1ft) apart in a band three rows deep, they filter the wind very effectively. They can grow over 240cm (8ft) high, but it is advisable to trim them back to 150-180cm (5-6ft) in late summer. This makes them more stable and encourages the tubers to swell.
Although less hardy, a belt of sweetcorn can similarly give useful protection to some of the more tender summer vegetables and herbs — dwarf French beans, tomatoes, green peppers,, basil and so on. And although not generally regarded as a vegetable in spite of its edible seeds, sunflowers make a magnificently picturesque and functional frame to any vegetable patch.