Greenhouses have advantages and disadvantages compared to gardens regarding the control of pests and plant diseases:
- it is easier to control the greenhouse environment than the open garden
- some pests flourish in greenhouse conditions
- some controls can be used effectively in the greenhouse but not in the garden.
Greenhouse Hygiene Practices
Good greenhouse hygiene practice is simple and though the routines can be mundane, they are worth the effort to maintain plant health. Good practice includes:
- Inspect plants frequently
- Remove any signs of damage or decay in the plants, their soil or the surrounding environment, to minimise the build-up of harmful bacteria
- Clean all pots, containers and equipment and avoid storing them in the greenhouse
- Regularly clean the greenhouse interior and exterior, including all equipment
Greenhouse glass often gets dirty quite quickly from dust and debris carried by the wind so a regular clean of the outside of the greenhouse will usually be necessary. This applies especially during the winter when the dust build-up can significantly reduce the amount of light available to the greenhouse interior.
The glass can be washed with a mild or diluted non-toxic disinfectant. On the inside of the greenhouse, this is best done at a time when the plants can be removed. The greenhouse can be lsft to air off before the plants are brought in again. Algae will develop in the spaces where the glass overlaps in most modern greenhouses, primarily due to the build-up of moisture. Such algae is best removed using a metal scraper of the type used for decorating. Used carefully, it will not scratch the glass.
Controlling Variables In The Greenhouse
As well as maintaining greenhosue hygiene by cleaning, the normal activities to control temperature, humidity, light and air circulation help keep plants growing evenly and healthily, thereby making them less susceptible to disease and pests. While specific equipment may be in use for particular plants, e.g. propagators for seeds and young plants, for the general environment the following methods apply:
- Keeping temperatures down by ventilation. Some pointers are described in Greenhouse Ventilation. Other aids to ventilation include using slatted rather than solid staging to aid air circulation. It is also good practice where possible to maintain space between plants and to avoid them being placed too near to the glass.
- Keeping temperatures up by heating, applying bubble wrap plastic to areas of the greenhouse or wrapping greenhouse fleece around plants and their containers
- Managing light by shading parts of the greenhouse using blinds, or applying a coating to the outside of the glass during the summer
- Ensuring that watering of the plants is regular rather than letting it become ad-hoc or infrequent, either of which will cause the plants to deteriorate
- Maintaining humidity by damping down, usually by soaking the floor and staging, or by the use of capillary matting or for large greenhouses, some degree of automation.
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