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