Growing Environment

The location of the growing environment needs to be thought through before any grow systems are set up.

Environmental variables such as temperature and CO2 levels may adversely affect plant growth (see environment control).

Indoors or Out?

The decision of whether to grow indoors or out is usually taken after the grower has considered outdoor environmental variables such as ambient air temperature, hours of light and weather.

These variables can't be controlled outside. Growing indoors brings its own set of advantages: temperature, light and CO2 levels can be controlled and weather outside will not usually influence growing inside. In many cases it is not whether or not to grow indoors but where indoors to grow.

Indoor growing areas can be constructed virtually anywhere in a household. A spare room, loft, old cellar and greenhouse are often used as an indoor growing area. A number of factors must be considered when choosing an indoor growing area.

Light

An indoor growing area often has little or no available light and a lighting system is usually rigged. Often it is better start with a completely dark area and then illuminate it rather than using an area which has available light through windows or skylights.

Rooms with skylights and windows will not provide adequate levels of light and may interrupt the lighting cycle the grower is trying to achieve. The grow room or greenhouse should also use a light reflective colour, ideally white, on the ceilings and walls. Dark colours absorb more light depriving the plants of this energy source essential to photosynthesis.

Special sheeting is available which helps reduce light loss. One form of sheeting, MYLAR, gives up to 92 % less light absorption whilst 72% can be gained when covering the walls with a black/white sheeting and 60% gained from painting walls and ceilings white. Light reflectors and light movers also help enhance available light and reduce light loss. These are discussed in our lighting article .

Atmosphere

The atmosphere of the growing environment must be considered when assessing the suitability of an area as a growing room. The need for fresh air circulating around the plants contradicts the need for high levels of CO2 required for growth and presents the grower with a dilemma. A sealed environment is not a feasible solution; within an hour plants are can reduce the level of CO2 in the surrounding atmosphere to less than one third of previous levels.

An extractor fan can be used to provide adequate ventilation and air circulation. However in order to maintain higher CO2 levels which fall as a consequence of using such a device it is recommended that the grower add CO2 to the growing environment.

This can be achieved using a CO2 gas bottle and regulator or a burner. These options are discussed in more depth in our environmental control article. Temperature can be maintained partly through the use of lighting - a certain degree of heat will be given off from the lighting system used.

Pests

The growing environment should be void of pests. These include not only animals such as the household cat and dog disrupting a hydroponics system but also pests of the micro variety. Insects can damage plants and traditionally chemical methods were used as a means of controlling them. However, as a consequence of the 'organic revolution' and a need for a more natural approach, modern pest control takes a biological approach to solving the plant/pest problem. The approach uses harmless insects to kill the more harmful plant pests. They act as a predator and kill the pest at a particular stage in its life cycle.

The two spotted mite (a.k.a. spider mites) are one of the most common and devastating pests experienced by a grower. These mites are barely visible to the naked eye and can reproduce to such an extent that a given crop is swiftly wiped out. Early signs of an infection are a general bronzing of the plants' leaves and as infestation increases so does the presence of fine webbing visible on the underside of the leaves. Whilst chemicals have traditionally been used in increasing strength to combat this pest, this has been to the detriment of non-harmful insect species also residing on the plant. For more information on spider mites please read our spider mite article.

The introduction of another mite (Phytoseiulus Persimilis), has been the biological solution to the spider mite problem. These mites feed exclusively on spider mites and reproduce in direct proportion to the level of spider mites available. If the mites cannot control the spider mite population then the grower can give them a 'helping hand' by adjusting the environmental variables so that the temperature and moisture are more suited to the predatory mites' vitality.

Whitefly is an example of another common pest which affects both amateur setups and commercially run greenhouses. The predator of the white fly is a small wasp, Encarsia Formosa which is harmless to everything except the whitefly. With a resemblance more akin to a fruit fly than a wasp, Encarsia is dependent on whitefly for reproduction as it lays an egg on the whitefly larvae which then become the food source for the developing larvae of the wasp.

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