A greenhouse is basically a very simple thing. By means of glass or plastic the sun's energy is trapped in the air and soil so that an enclosed space is warmed allowing plants to grow optimally. While the principle of the thing is very simply the devil, as they say, is in the detail.
To get the most out of your greenhouse you are going to need some supplies to make it an efficient system. Your aim is create in an artificial environment the best growing conditions for plants that would not normally thrive in northern latitudes or at high altitude. Your plants need warmth and humidity, but they also need ventilation because without a good air flow disease can result.
You also need to get the maximum number of plants into the relatively small space of your greenhouse. Whether your aim is fruit and vegetables for the kitchen or exotic flowers for the house or show bench you need to exploit your greenhouse to the full extent of its potential. Otherwise it just becomes inefficient. A greenhouse is an intensive system.
Even you rely only on the sun's rays to heat your greenhouse and do not have any form of supplementary heating you will need to think about a range of equipment. You will certainly need a method of venting the greenhouse. On a sunny day a greenhouse can become too hot and plants will suffer. The simplest method is to walk out there and open the door and a window. But if you are at work all day or plan to take vacations that is not a satisfactory solution. An automatic system of ventilation for the greenhouse is the answer.
Automatic ventilation may be as simple as an electronic mechanism that opens a window or a more elaborate system of fans. They are triggered by a thermostat. You can start with something basic and invest in a more elaborate system as you develop your greenhouse.
The same is true for watering. I could walk out to the greenhouse with a watering can. But do I want to do that four or five times a day in high season? Even the most enthusiastic grower might hesitate at that. No, an automatic watering system is the answer even for a small greenhouse. It can be quite simple. A passive system using capillary matting is cheap and easy to maintain. At a more complex level there are systems of drip feed pipes that deliver water to the plants.
For all the year round growing a greenhouse will certainly need lighting. Lights will extend your growing season. There are a number of types available for greenhouses.
Bringing power to the greenhouse is a skilled job. Get an electrician to install an outdoor power supply if you do not already have one. The control systems themselves can be built by an enthusiastic amateur. The parts are available at electronic hobbyist suppliers. Most of us would probably prefer to buy them ready made. They are a good investment in the long term because they will ensure the best conditions for your plants and allow you to take a break.
You should also think about how you intend to grow your plants. Will the plants be in containers on benches or will they grow in the ground? Plants will grow quite happily in the ground. But if you grow the same kind of plant year after year in the same place there can be a build up of disease. The traditional answer to this problem was to replace the soil in the greenhouse annually. That must have been back breaking work. A better solution is to use a growing medium that can be replaced annually. A commercial potting compost is an ideal solution. These are usually light to handle because they are based on peat or, even better, coconut fibre or bark which are both sustainable resources.
Benches, or greenhouse staging, is very useful. Smaller plants or seedlings can be placed at a higher level. They also provide space for mixing compost and repotting plants. If the greenhouse is to be used by someone who has mobility problems then this becomes even more important. A gardener with limited mobility can derive great pleasure from a greenhouse if it is planned properly. Good access is important for all gardeners but especially so for those with mobility problems. A path of well laid paving stones is essential for any greenhouse.
