If you are fortunate enough to have a greenhouse, or are planning to install one in your garden, you should be aware of how important cleanliness is. By keeping your greenhouse clean, you will have much more success in your plant growing. So what needs to be done?

Glass
Obviously, your greenhouse is primarily made of glass or some other transparent material such as polycarbonate. This allows plants to receive as much light as if they were outdoors, while being afforded the protection and warmth of being indoors. However, dirty glass can reduce the amount of light significantly. Even a thin film of dirt can have a great effect on the light levels within the greenhouse. It may not seem any different when you are in there, but don't forget that not all light is visible, such as ultra-violet light.
With reduced light levels, plants may start to grow tall and thin as they reach for as much light as possible, so keep your glass clean.

Just as you might was your house or car windows, you can use a simple soap and water solution to clean the glass. Rinse it off with clean water and allow it to dry naturally.
You might also want to use a little disinfectant in the water to kill off any bacteria.

Floor
Some people site their greenhouses on the bare earth, but many use a prepared concrete or stone floor. If that is the case, sweep up any compost or soil, and dead or pruned plant matter. Dispose of it in your composter if you have one. Leaving these materials on the floor can harbour insects, slugs, snails and even plant diseases. It can also be quite unsightly.

Plant Pots
Most gardeners seem to accumulate a large number of plant pots - usually small ones that came with plants and seedlings in them. Once you have removed the plant from them, if you are going to keep them for re-use, then wash them straight away. This helps to keep the greenhouse clean and also removes any plant diseases that may be present in the compost contained within them.

Garden Tools
Clean your tools after you have used them. Again, this can help prevent the spread of plant diseases, but it also prolongs the life of the tools and makes your gardening more pleasurable. There's nothing worse than coming back to tools caked in dried-on mud.

Storage
Don't be tempted to make your greenhouse into an annex to the garden shed. Store bags of compost, spare plant pots, tools, the lawnmower, the barbecue etc., in the shed; not in the greenhouse. Again, by keeping these things around, they can carry pests and diseases.

Spider Webs
Although spiders don't do any damage to our plants directly, their webs tend to catch dust and dirt, and bits of leaves etc.

Before You Plant
In the spring, before you sow any seeds or put any seedlings into your greenhouse, take everything out of the greenhouse and give it a thorough cleaning. Don't put anything back that you don't need for the growing season.

Consider using a sulphur (sulfur) candle, which you can obtain from most garden centres. This consists of a tin of sulphur grains and a wick. When you burn the candle, it emits a thick smoke which sterilises the greenhouse by killing almost anything - whether it is insects, slugs, bacteria or fungus.

Remove any plants from the greenhouse and close all the windows. Ensure that there are no animals such as cats in the greenhouse. Place the candle in the middle of the greenhouse floor and light the wick. When you're sure it is burning properly, leave the greenhouse immediately and close the door. The smoke produced will fill the greenhouse and kill any insects, slugs, snails, bacteria etc. Don't be tempted to open the door or go back into the greenhouse for several hours - read what it says on the tin and obey it - that smoke is very nasty.

After the smoke has cleared, open the greenhouse door, and let the fresh air clear the remaining fumes out.

You only need to use the sulphur candle once per year, but it's worth doing. The author has had much less trouble with slugs and snails eating his plants after using a sulphur candle before planting.

By keeping your greenhouse clean, you are more likely to get stronger plants, which result in better crops. You may also find there will be less need for other chemicals such as slug pellets or insecticides if you find that you usually need to use them.