SIZE Modern greenhouses are available in a wide range of sizes to suit all purposes and pockets and the choice will depend entirely on the resources and requirements of the owner. There are, however, one or two general rules which should be observed. It is important to be absolutely sure that the structure chosen will be large enough. Although at the outset a greenhouse may seem too large, in a few months the keen gardener will have it full to overflowing with his favorite plants. On the whole very small greenhouses are more difficult to manage than larger ones for comfortable working the minimum width of a span-roof structure should be at least 8ft (2.5m). This allows for a centre path 2ft 6in (75cm) wide with benches 3ft (1m) or slightly less in width on either side. If the width is less than 8ft (2.5m) the path will still have to be the same width which leads to a serious reduction of the effective growing spaces. In a greenhouse 8ft (2.3m) wide, a 2ft (60cm) path equals 23 per cent of the floor area, but in one only 6ft (2m) wide, it will represent 33 per cent of that area. Height is equally important. There must be sufficient head room for taller plants, and it must be possible for the gardener to stand upright in comfort when tending the plants. An 8ft (2.5m) wide greenhouse which is 5ft (1.5m) high to the eaves and 7ft 6in (2.4m) to the ridge will give a height of 6ft 9in (2.23m) at the front of the bench which is adequate for most people. Most greenhouses are available in multiples of a unit length and it will simply be a matter of choosing a length to suit one’s requirements.
GREENHOUSE DOORS these can be either hinged or sliding. Many of the modern greenhouses have sliding doors which are a great advantage when space is at a premium. One disadvantage of this design is that grit is liable to foul the base runners. All doors should be wide enough to allow for the passage of a wheelbarrow.
DUTCH LIGHT GREENHOUSES these were originally evolved in Holland as commercial greenhouses but, like many other good horticultural ideas, they have been adopted by amateur gardeners. The lights can be clamped together with special clamps or secured to a framework specially constructed for the purpose. This skeleton of uprights, rafters and ridge timbers can easily be built by the amateur gardener with a working knowledge of carpentry. On the basis of cost per square foot (.0929m2) of growing space, the Dutch light greenhouse is the cheapest glazed structure there is. The initial cost per square foot (.0929m2) of a polythene tunnel is less but the polythene needs replacing every second or third year. Small greenhouses of this type are now made by several manufacturers, but they are mainly an adaptation of the Dutch light principle using Dutch light-sized glass. The majority are made in cedar wood, with glass to the ground, and are extremely useful for the amateur, particularly those who are interested in growing tomatoes and chrysanthemums.