One of the best things you can do to make sure your plants grow at optimum speed is to look after the temperature and try to give them constant warmth. In the spring time this can be difficult, but here are a few tips as to how you can do your best to keep temperatures high, and consistent.

Plants aren’t human, they don’t have feelings and moods. They are simply a load of chemicals jumbled together, and each type of plant has it’s own slightly different composition, which is why some like damp, some like dry, some like heat and some cold. High temperatures are a big part of what makes chilli plants grow, and when the temperature is right for them, they grow, and when it isn’t they don’t. Look at weeds in the hedgerows, one week nothing, next week a foot high. You want your chillies to go from an inch to a foot quickly, so let’s get the temperature right.

For optimum growth rates you should be aiming for a constant 27-31°c during the day, and slightly lower at night, say 23-26°c. At these temperatures your chilli plants will almost grow before your eyes, and maybe two or 3 times the rate of something kept at ‘room temperature’ with a bit of extra sunshine during the day.  Put simply, they will grow when the temperature is right, and stop when it isn’t, so any extra time or money you can spend on maximising this growing period will be rewarded with better results.

1. Firstly, and probably most importantly; remember, half the plant is roots, so soil temperature is at least as important as air temperature.
2. A heated propagator – For germination and for young plants this is the easiest way to keep them warm. When they have germinated and are growing nicely, you can remove the lid and the warm tray will continue to keep the roots warm.
3. Soil warming cable – For a larger number of plants, and if you can afford the luxury, then this is the best way of optimising soil temperatures to grow your plants as quickly as possible. It means you need a big sunny window if not a lovely greenhouse, with a big tray or specially constructed bench, a purpose bought warming cable, some insulation and some sand or inert substrate. Then you can thermostatically control the temperature of the roots of your plants accurately.
4. Let sunshine get to the pot – When sunshine is hard to come by arrange your pots so they get the maximum benefit. If they are in a position where the side of the pot is exposed to direct sunlight, then the warming effects of the sun will mean the pot and therefore the roots are warmer than the surrounding air.
5. Use black pots rather than the traditional red ones. These are often cheaper and they absorb the heat of the sun more.
6. Bigger pots – there is no harm in potting small seedlings straight into their final big pots, the big volume of soil acts as a heat sink to keep roots warm long after the sun has disappeared. It also stops the big temperature fluctuations that small pots suffer from. Beware – if big pots are kept in a cold place and never get a chance to warm up, then the opposite will happen.
7. Move them around! – The simplest job is sometimes the hardest as it involves time and effort. Put them in the greenhouse or the sunny window during the day and move them into a warm room at night. The more you keep them at their optimum temperature, the more time they will spend growing.
8. Hydroponics – This is a more expensive alternative than traditional pot growing, but once you have made the initial investment of time and money the rewards will be higher with quicker growing plants, bigger plants and ultimately more chillies. Depending on your setup, the root temperature, and possibly that of the whole plant, are thermostatically controlled. Top this with the perfect nutrient mix and you will be way ahead of the competition.

Remember there is more to it than just heat, you need to juggle all of these tips with lots of lovely bright light too.