Gardening Under Cover – Greenhouses, Cloches, Conservatories

Shelter from the Weather

Grow more crops and flowers for more months in the year, and be warm yourself

Much of being a naturally successful gardener is about fitting the plant to the micro-climate. The most radical way of affecting the micro-climate is to grow the plant under cover. In warm countries this may be done to provide shade and/or cooler temperatures or to alter the day length, but in much of the world many plants are grown under cover to keep them warm. Cover allows various degrees of control over the plant’s environment depending on the investment.

A cloche or two will extend the season, and a coldframe allows a wider range of plants and more successful propagation. But a greenhouse, conservatory or polytunnel, especially if kept frost-free, opens up whole new areas of gardening — if heat can be afforded then you can easily have your own pineapples or bananas! If you have part of your garden under cover, you’ll spend more and more time there because being in the warm and out of the wind makes many more days a year gardening days!


Gardening under cover

Gardening Under Cover - Greenhouses, Cloches, Conservatories Cloches of any size create significant weather and pest protection, and allow the keen gardener to extend the growing season by several weeks at both ends. Their clever use makes possible a wide range of plants; indeed melons and grapes can be successfully grown under cloches even in the north of England. However, the traditional cloche has now been widely replaced by low plastic tunnels, but these are not as warm at night as the old glass ones. In either case, some ventilation is always required on hot days and extra cover at nights, if full use is to be made of cloches.

Where they are only used temporarily, cloches cause no problems, but after a time they can cause dryness underneath if rainfall is patchy and not heavy enough to soak sideaways under the cloche. Cloches are most useful for getting earlier crops of favourite vegetables, and they are best set in place a week or two early to pre-warm the soil. They are then used for protecting young tender plants, such as tomatoes or courgettes, and after can be full with melons all summer. In autumn, they can cover crops to keep the weather off and are ideal for saladings through the winter.

Large plastic water bottles with the base cut off and the cap removed make excellent cloches for individual young plants. It is easy to make cloches by using several bottles held together with waterproof clear tape to make a box and a lid of glass or plastic. Do not cut the bottoms off as a little water in the bottom of each will prevent the cloche blowing away and if the lot are filled with water this acts as a heat reservoir. On cold nights, they could even be filled with warm water from the house to give extra protection. Later in the season, making a small hole near the bottom of each will allow trickle irrigation when the cap is removed. Clear plastic bottles full of water can be used piled up just like bricks, to build a sheltering cloche around a treasured plant while it establishes.

Coldframes are the next stage, and these are usually sited in a warm sunny spot. The better ones are snug and well insulated. The better they are made the better job they will do, but the more careful you need to be not to cook the plants by leaving the lid closed on a sunny day. A coldframe can be covered at night with a blanket and kept frost free for longer through the year by popping in bottles of hot water. This then allows you to start off many more of the tender plants and to grow them on before planting out in late spring or early summer. In summer, a coldframe can produce some good crops of cucumbers, peppers or even a decent melon or two.

A coldframe is also useful for propagating plants from seeds and cuttings and over-wintering nearly tender plants. With a soil-warming cable or a compost heap or hot bed underneath, you can achieve great things — even very good crops of excellent melons. However, you are then really better off putting the whole set-up under walk-in cover.


Greenhouses and plastic covered tunnels

One of the most useful, if time-consuming accessories to a garden, is walk-in cover. This is much better than using cloches or coldframes for shelter and warmth because the extra volume of air gives a more stable environment, and it allows the gardener to work in comfort! Why should the plants alone have good conditions? A greenhouse or a plastic-covered tunnel, a polytunnel, can be used for giving most plants a really early start and provide protection from pests and the weather. They can also be used for growing winter salads or flowers, for growing plants a little too tender for outside, and for forcing or protecting fruit trees.

Gardening Under Cover - Greenhouses, Cloches, Conservatories A greenhouse is lighter and warmer, and usually the frame is easy to use as a support for staging, potting benches or plant supports. This makes a greenhouse more suitable for plants in pots and perennials. Wooden-framed ones are more aesthetically pleasing in a garden, are warmer, but need regular maintenance. Metal-framed ones last longer, but are ugly. A polytunnel is uglier still, much cheaper but colder, may be very humid and is harder to ventilate. The plastic cover needs replacing every few years which makes it poor value ecologically, but does give the opportunity, where space allows, of moving the whole thing making rotation possible. As the frame is unsuitable for fixing benches or staging they are most useful for growing annual or short-lived plants directly in the soil.

Whatever you buy, get the biggest you can afford. The larger they are, the better value and the more stable the environment produced. Site them with their longest axis east—west to maximise sunlight and do not put them in heavy shade. Make sure you have water close by, and electric light and power allows evening work and the use of heated propagation. Make sure everything is securely built and have adequate ground fixings against strong wind.

A double-skinned polythene tunnel is a mixed blessing. Although the two layers of polythene keeps plants warmer, it reduces valuable light too much. However, in winter I use triple layers of polythene and add supplementary lighting because it is cheaper than heating a single-sheet polythene tunnel. Ventilation must be adequate for hot weather and automatic unless you are at home all day. Money spent fitting automatic heating, ventilation and watering systems will be recouped in terms of time and better growth and more than doubles their value.

Conservatories are different. Originally the term was for a plant room which you visited. Now a conservatory is an extra living room attached to the house and you live in it, so the plants cannot necessarily have first call. Your partner may object to a potting bench next to their seat, and guests may wonder as your house becomes a greenhouse-come-garden shed — mine has! However, a conservatory can be easily heated and it is a perfect place to be on most British days! It is nice for you and for early spring sowing and potting up seedlings. Ideal for the small plants, but they do get in the way — and worse. The problem is that the conditions we live in and what plants need are very different; most plants want it much more humid. So humid, that our furniture and household goods tend to mould and rot.

So the ideal conservatory subject is a cacti or succulents, or any plant that likes dry atmospheres — pelargoniums can become monsters. Many other plants can be kept in a conservatory, but will appreciate spraying with water regularly to keep them happy. In a shaded conservatory with no direct sun then foliage house plants will be most successful. Ideally grow conservatory specimens in pots, then they can go out in summer — or in winter, as many deciduous plants, such as peaches and grapes, need to go dormant and this is usually during a cold period. If planted in the border of a conservatory, these would never get cold enough for long enough.

06. January 2011 by admin
Categories: Greenhouse Gardening | Tags: , , , | Comments Off on Gardening Under Cover – Greenhouses, Cloches, Conservatories

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