ADVICE ON THE SITE FOR YOUR GREENHOUSE

Many greenhouse or "garden experts" simply advise that your greenhouse should be sited with its ridge running East to West. This is generally advised because it means that the best light is then available all down one side of the greenhouse.

ADVICE
When deciding where your greenhouse is to be sited make sure that at least a part of one side or even the back end of the greenhouse will capture as much of the southerly light as possible. Then you will be assured of achieving strong healthy early growth. As a basic rule of thumb the "experts" advice may be correct but it is not as simple as that.

Firstly consider the trees in your garden and those in your neighbours garden too. Keep in your mind that throughout the spring months the light is coming from the sun which is low in the sky at that time of the year. Trees in the area shouldn't be shading your greenhouse for most of any day during the winter and spring months and you should not consider a position underneath trees. Little harm can be caused by deciduous trees as when the light in spring is at its lowest they will not have leaves and can be a bonus in the summer months when they do have them, by giving valuable shade.

Then consider whether your house or your neighbour's house throw shadows across your garden and at what time of the day, again remember the lower light in the spring months. 

Any fool can germinate a seed but its the seedling that must have adequate, good even light.  It is important that your new seedlings or cuttings grow into well proportioned healthy plants and this can only be achieved by allowing them good all round light for as much of  each day as possible, particularly during the critical early months of the year. If you don't have the best light available then all you will achieve are tall leggy plants and disappointing end results.  Have you tried propagating seeds on the window cill in the kitchen and look what happens - seedlings are fighting for light, they get leggy and never turn out to be very healthy successful plants.

ADVICE
you must also consider the accessibility of electric, water or gas, to your greenhouse and its convenience to you. You need to ask yourself questions like :

Am I going to need to heat the greenhouse during the winter months ?
If you do then a supply of electric or gas must be easily available.

Am I going to be happy reeling the hose pipe down to the greenhouse everyday ?
If the answer is no then you must employ a plumber to provide a permanent supply and tap near to your greenhouse.

Please turn to a local qualified Plumber or Electrician, don't rely on an odd job man, landscape gardener or a greenhouse erector, especially where electrics are concerned as special fittings are required for humid areas such as greenhouses.  I have personally seen the efforts of an odd job man who nailed cabling to a panel fence and brought the cable at neck height across to the greenhouse which inevitably caused an accident.  Only special cables must be used for outside electrics, well protected, fixed onto a solid surface or sufficiently buried.