How to Choose a Greenhouse and Where to Put It
Choosing a Greenhouse
with an aluminium framework are relatively cheap and need very little maintenance. They let in more light and lose more heat than wooden ones, although in most amateur you will be unlikely to notice much difference. The variation in price between the same-sized greenhouse from different manufacturers usually reflects how sturdily they are made, ie. how much material is in the framework and the method used to fix the glass.
Many people prefer the appearance of wooden greenhouses. They can be made of cedar wood, which is expensive but naturally durable, or cheaper but less durable woods such as teak Cedar wood can last up to fifty years without any chemical treatment, but other woods should be pressure-treated with wood preservatives by the manufacturers, and will need further regular treatment to prevent rotting.
The manufacturers should also be able to tell you whether the wood comes from sustainably managed plantations. Cedar, for example, takes from seventy to ninety years to grow, and conservation groups claim that the timber used at present is destroying natural forests.
You may find that timber frameworks are more difficult to keep scrupulously clean.
UPVC (a type of plastic) is used for the framework of some modern greenhouses and conservatories. It is durable and relatively maintenance-free. However, structures made from this material often need double glazing and a polycarbonate roof to give them sufficient strength. This makes them well insulated, but expensive.
Glass is more durable and attractive than the plastics used to clad greenhouses. It provides much better conditions for plants: it lets through more light, traps the heat more effectively, and gives fewer problems with condensation. Also, it is easier to clean.
Horticultural glass is thinner and less expensive than ordinary glass; however, any glass is easily broken or cracked accidentally, and panes must be replaced quickly.
Plastics are lightweight and easy to handle, but tend to discolour or become scratched, which can cut down on the amount of light transmitted.
Rigid plastic-like polycarbonate is very strong and durable and is often used for roofing greenhouses where glass would be too vulnerable. It is manufactured as a double- or triple-walled sheet, which gives it good insulating properties. However, it is more expensive than glass and has only about 70-80 per cent of the light transmission.
Choosing a site
To be of most use, a greenhouse needs to be in a position where certain conditions prevail.
Plenty of light
This is needed for as much of the day as possible, especially in winter. To get the best light, site the greenhouse away from buildings and trees. Remember, shadows will be much longer in winter than in summer. If possible, align a traditional barn-shaped greenhouse with its ridge running east—west.
Shelter from strong winds
Trees and hedges which are far enough away not to cause undue shading can still provide useful shelter from strong winds, which cause loss of heat as well as physical damage.
A free flow of air
For example, do not choose the bottom of a slope, as cold airdownwards and forms a frost pocket where icy air collects.
If plants are to be grown in theborders, then choose ground that is well drained, otherwise you may need to install drains.
At least one border of reasonably fertile soil is preferable if you want to grow cropping plants.
Easy access to piped water makes watering more convenient. Electricity, although not essential for heating, is useful.
Easy access to the house
The easier it is to get to the greenhouse, the more care plants are likely to get. A lean-to greenhouse on a house wall has an obvious advantage regarding access. It will also stay warmer, because one wall is brick (which retains heat) and it will benefit from the heat escaping from the house.
You will need to be able to get to the greenhouse with a wheelbarrow for carrying soil, compost, and large pots.
This is useful for standing plants in pots and, possibly, for cold frames.