Gardening Vivian | 06 May 2011 11:13 am

Greenhouse System – What All Expert Gardeners Know

The greenhouse is a system that attempts to mimic the natural system in which plants grow in the wild. We must aim to provide the plants with water, light, heat and nutrients in the right quantities and at the right time for the plants to thrive. Not only that but we must aim to go one better than nature and to fine tune the greenhouse system to the point where it produces the maximum output for the minimum possible input.

The money we spend on lighting, heating and watering our greenhouse, feeding the plants and treating them for pests and diseases are the inputs. Our own time is another input and one that is often in short supply. Few of us can spend as much time as we would like in the greenhouse.

Outputs are the fruit, vegetables and flowers we harvest from our greenhouse. Somewhat less quantifiable are the physical and psychological benefits we derive from working in the greenhouse. Growing plants is a recognized way to combat stress and depression.

We want to get the most output we can from our greenhouse. Maximizing the crop is not incompatible with the personal benefits because it is a pleasure to be in a greenhouse that is working well.

It will help to think of the overall greenhouse system as a number of interconnected subsystems. When all these systems are working in harmony then the greenhouse as a whole will function effectively.

There are four basic subsystems: water, heat, light and nutrients. Let us look first at water.

Water is important because it carries nutrients to the plants’ roots. It is also important to the leaves of the plant which need water to manufacture food. The atmosphere of a greenhouse needs to be moist as well as the growing medium.

Simple manual watering is often not enough when plants are in rapid growth. An automatic watering system is the ideal way of providing the correct amount of water. It can be set on a timer depending on the growing conditions and the stage of the plant’s life.

The air in a greenhouse can be kept moist by misting. Automatic misting systems are available. A reservoir of water will also help.

When water is an expensive input because it is metered then rainwater should be collected. A water barrel will store water from the roof of a house and the greenhouse. It can then be pumped into the greenhouse. Small and very reliable pumps are not available for this purpose.

Heating is perhaps the most expensive input and needs to be controlled carefully by a thermostat. There is no point in having a heater on when it is not necessary. You must carefully monitor the temperature in the greenhouse and outdoors.

Insulation is good idea during the winter. This will allow you to reduce your heating bills.

Light is usually plentiful and mostly free. It only becomes an issue in the winter when the day length is short and the sky cloudy. Some artificial lighting may be necessary in a greenhouse.

The problem that light presents is that there can be too much of it. Plants easily burn in a greenhouse and shading is vital in summer.

Nutrients are vital for plant growth. You must feed the plants if you want the best results possible. The most controlled system of plant nutrition is the hydroponic system in which plant roots are suspended in a nutrient rich solution. Plants can even grow on a pane of glass if a thin film of nutrients is constantly passed over their roots. This works well in a greenhouse setting.

When all these subsystems are working well then there will be little trouble with plant diseases and pests. Where these occur it is necessary to look at heat, light, water and nutrient levels.

In theory it is possible in a large enough greenhouse to have a completely closed system with no external inputs except sunlight. The plants themselves would produce their own food and maintain the correct level of moisture. Reptiles and insects would eat pests. There would be no need for human intervention. That is not realizable on a small scale and not desirable since we want to harvest the crops our greenhouses produce.

The human element is the most important part of your greenhouse system. You are its control system. You must train yourself to do it well. As you gain experience and read about the subject you will become more proficient and your greenhouse will begin to function as an efficient system.

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