| Greenhouses are available in all shapes and sizes, | | | | troublesome step or ramp.Heating is desirable, but |
| and take forms that vary from the conservatory | | | | may be prohibitively expensive. If you do decide |
| to an enclosed glass porch around the front door. | | | | to heat your greenhouse then purchase an |
| All are very useful for the hobby gardener and | | | | electrical fan heater. Not only does this provide |
| can accommodate a surprisingly large number of | | | | warmth, but it also circulates the air on damp |
| plants of all kinds.Modern greenhouses basically | | | | days in the fall. In the summer the fan can be |
| come in four forms; the lean-to, in which one wall | | | | switched to the cool air position to reduce the |
| is formed by the home or other substantial | | | | high temperatures and provide air circulation. |
| building; the span roof type, which is built on a | | | | Propane gas and kerosene heaters, although very |
| dwarf wall and has a pitched roof; the Dutch light | | | | reliable, are not so desirable as they produce a |
| kind, formerly constructed of Dutch lights but in | | | | damp heat, and by virtue of their mode of |
| the modern form a glass-to-ground greenhouse, | | | | operation do not readily circulate the air.If you are |
| and the hexagonal type that is, broadly speaking, | | | | able to afford to heat your greenhouse, it also |
| dome-shaped but with angular sides. All have their | | | | makes sense to insulate it to minimize heat loss. |
| adherents, but it is generally conceded that the | | | | There are many methods of doing this, but the |
| span roof type of greenhouse proves to be the | | | | clear plastic bubble insulation material now available |
| most versatile when a wide range of plants are | | | | is simple to fix and rarely causes any problems |
| to be grown.Greenhouses can be constructed | | | | with condensation. Clear polyethylene has always |
| from many different materials. Polyethylene | | | | been considered to be the most suitable insulation, |
| structures are cheap to purchase initially, but need | | | | causing minimal reduction in light and trapping a |
| re-covering every two years and in winter will | | | | barrier of air. However, it has always been |
| often suffer wind or snow damage. Those made | | | | associated with condensation, a build up of |
| from corrugated acrylic sheet are little better, | | | | light-reducing algae, and a fragility which is not so |
| cracking and discoloring with the weather, although | | | | evident in modern clear bubble insulation.Whatever |
| polycarbonate materials are more durable and can | | | | insulation you choose, it is important when |
| be recommended.Glass is obviously the most | | | | fastening it to the internal structure of the |
| satisfactory option, but the best material for the | | | | greenhouse that provision is made for the opening |
| framework is more difficult to decide. Cedar and | | | | of ventilators. Insulation may well still be useful at |
| teak that are kept well oiled are obviously ideal, | | | | night during spring, but on sunny days the |
| but very expensive, while ordinary softwood | | | | temperature will soar and full ventilation may be |
| painted white looks good but has a very limited | | | | necessary. If you cannot afford to heat your |
| life.Aluminium would seem to be the best answer | | | | greenhouse, then consider investing in either a |
| as it does not rust, but with some greenhouses | | | | small propagator or a heated bench. Both are |
| the bolts and screws holding the structure | | | | very useful and give the greenhouse much |
| together are made from steel and are liable to | | | | greater versatility.Correct siting of the greenhouse |
| corrode. So inspect any intended purchase of this | | | | is vital if plants are to develop properly. Choose |
| kind very carefully, and select an all aluminium | | | | an open part of the garden in full sun. It is a |
| model.Ideally staging should be provided at waist | | | | simple matter to shade a modern small |
| height down either side of the greenhouse and a | | | | greenhouse if the sun becomes too bright. The |
| shelf near the ridge is very useful if this can be | | | | uncontrollable shade of a tree or building on the |
| kept above head height. Ventilation must be | | | | other hand can lead to very poor and |
| adequate and most gardeners agree that both | | | | disappointing plant growth.Philip Swindells has over |
| side and ridge ventilators are essential for proper | | | | 40 years gardening experience. A former |
| airing during the summer months. A good wide | | | | botanical garden curator and an international |
| door is necessary for easy management. It | | | | horticultural consultant, he has worked extensively |
| should be wide enough to take a wheel-barrow | | | | in the UK, North America, the Middle East and |
| without skinning your fingers and with no | | | | Australia. |