Plant Protection from Weather
The gardener not only has to protect his garden plants from pests and diseases but also against unsuitable weather conditions. Methods to combat these troubles are suggested here. Many gardeners evolve methods which suit their own requirements.
For centuries the gardener has used glass to protect his less hardy plants and there is a wide choice of design in modern greenhouses, frames and cloches. Although an unheated greenhouse affords some protection against frost, some form of artificial heating is needed if the house is used for over-wintering tender specimens or for an early start with such summer crops as tomatoes and cucumbers. Frames heated by a pile of fermenting manure were once a feature of British gardening. Nowadays, soil-warming equipment is available for the same purpose. Cold frames and continuous cloches play a very important part in the kitchen garden. Both types of protection are used to over-winter young plants of such hardy plants as cabbage, lettuce and onions. During spring, frames and cloches protect seedlings and plants from cold as well as from heavy rain and icy winds. In summer, frame and cloche crops receive protection from the vagaries of the climate which may unexpectedly produce an August frost at night. Clear Polyglaze and other plastics are substitutes for glass but many modern gardeners continue to prefer the original material.
Protection against excess sunshine During the hotter part of the summer excessive sunshine and heat may lead to scorching of plants under glass. Lime wash or one of the proprietary shading compounds may be used. Alternatively, blinds may be fitted in the greenhouse or green Polyglaze sheeting pinned into position and removed as and when necessary. The cold frame may be covered with a few sheets of newspaper and a piece of old lace curtaining provides adequate temporary shade for clothed crops. Adequate ventilation is also of great importance during the summer months and, unless you are at home all day, it is far better to prop up the frame light and to leave the greenhouse door ajar than to leave both closed on a dull morning and, on your return in the evening, to find the plants suffering from scorch or heat exhaustion.
Protection against cold Seedlings and young plants in the cold frame or under cloches are liable to suffer from late spring frost. When a frost is anticipated, mats or sacking should be laid over cold frames and cloches at evening and removed in the morning. During late spring all cloches may be in use and none is available for sowings of half-hardy vegetables. Jam jars and preserving jars may be brought into use as miniature cloches. The seeds are sown where the plants are to grow and a jar set over each seed station. The jars not only give protection to the seedlings but may be left over the plants until they need more room. Half-hardy plants, raised in the cold frame or purchased from shops, may have to be set out in their growing positions when there is still risk of late spring frost. Protection against night frost damage may be provided by covering each plant with a paper cap. The caps need be no more than pieces of newspaper twisted to the shape of a dunce's cap. Set the caps in position in the late evening and remove them in the morning. Weigh the edge of the paper down with a few stones to prevent them from being blown away by wind. Some perennials need a little protection against severe winter cold. After cutting off the foliage to soil level in the late autumn, place a piece of wire mesh netting, bent to form a low tent, over each plant. Cover the 'tents' with a thick layer of straw or bracken. Retain the straw in position by covering it with another piece of wire netting. The lower piece of netting prevents the straw from being pressed on to the crowns of the plants, which may cause them to rot.
Protection against wind Living windbreaks are suitable in some areas and the blackberry is a good plant for this purpose. Plastic screens, made by nailing polythene sheeting to a light wooden framework, give temporary protection from wind around newly-planted shrubs and trees. Wattle hurdles, hessian sacking nailed to strong posts or even branches of evergreen shrubs afford similar temporary protection.
Lath houses A framework of thin wooden laths can provide protection for plants placed underneath it. The protection it affords can be from strong sunlight, wind and, to a certain extent, frost. Such protection is ideal for producing a cool, airy standing ground for many plants. Usually the framework consists of a span roof supported at the sides by upright posts spaced at not less than 2m (6ft) intervals. A simpler version can be constructed with a single pitch or span. This usually has a slight slope to one side. The laths used should be thoroughly treated with a horticultural grade of preservative or rot-resistant timber can be used, such as cedarwood. The laths are about 3cm (1.5in) wide and 1cm (1/2in) thick. They are spaced about 2.5cm (1in) apart.
Another form of protection is the use of frame lights supported on a simple wooden framework. The height of this framework will depend on the crop which it is to protect. It can be as high as 1.3-1.6m (4-5ft) if plants such as chrysanthemums are being covered. A span roof or a single sloping span should be provided. The main supporting rails should be selected from a minimum timber thickness of 5 x 5cm (2 x 2in). If planks are available, 16 x 2cm (16 x fin) will be ideal. The main rails should be nailed or screwed to uprights spaced not more than 2m (6ft) apart along the rows. The timber for these must be at least 5 x 7cm (2 x 3in) with 46cm (18in) in the ground.
Additional protection can be afforded with the frame light technique if the sides are covered in with hessian which can be tacked to the supporting rails and the uprights. A miniature greenhouse can be made in this way.