Some like it hot: fire up the spiciness of your chillies

·3-min read

We all have our gardening heroes, and for me it is without a doubt Dr DG Hessayon. He’s the author of the best-selling “Expert” series of gardening books which, despite being written almost 50 years ago, are still relevant today.

Humans seem to have discovered a weird masochistic love for the flavour of pungent plant defence compounds

One or two lines stand out in 2020. The first is a description of garlic as a pungent crop, which is a favourite of the “continentals” but will never become popularised in Britain. “Use it sparingly or you will be put off forever,” he advises. That’s before we get the good doctor on to the subject of chillies, which he warns no one should ever attempt eating under any circumstances unless they are part of their heritage. As someone who religiously follows everything Dr H says, I tell you I breathed a sigh of relief for my Malaysian genes at that one.

Given the explosion of specialist chilli nurseries, chilli-growing societies and even chilli-eating competitions that have cropped up in the UK in the past two decades, it is fascinating to me how fast some cultural aspects of gardening evolve. What is particularly intriguing is that the very reason readers were once warned off touching the crop is a key part of their current appeal: their fiery flavour. So, if you love the burn, here are some geeky tips to dial up their spiciness at the height of the chilli-growing season.

Feel the heat: dried chillies.
Feel the heat: dried chillies. Photograph: Alamy

Chillies are given their heat by the chemical capsaicin. This, it is thought, functions as a mammal deterrent. Birds can eat unlimited amounts of chilli with no ill effect, and act in nature as the plant’s key means of seed dispersal as the seeds pass through avian guts unharmed. As mammal digestive systems degrade chilli seeds, however, the plants have evolved a pungent defence specifically to prevent us from eating them. As is often the case, humans seem to have discovered a weird masochistic love for pungent plant defence compounds. But here’s the even weirder thing…

Although the amount of capsaicin a chilli plant is capable of producing is largely genetically determined, environmental stress can also dramatically increase how much the plant generates. The secret lies in three factors: temperature, light and water. Heat stress triggers capsaicin production, so for maximum fire grow chillies indoors if possible. A greenhouse is ideal, the top shelf of a greenhouse (as hot air rises) is even better. Studies have shown that increased light levels have a similar effect. So pick the sunniest spot, or put reflective panels beneath the plant. Trials have demonstrated that these bounce light on to the leaves, with similar results. And if reflective panels sound technical and tricky, lining the greenhouse shelf with tin foil will work just fine.

Finally, being lazy with watering works in two ways. First, it induces drought stress, and second, it reduces the water in the cells of the fruit, concentrating their spiciness. Three simple and really effective tricks to fire up your crop, based on solid science – but don’t say I didn’t warn you before tucking in!

Follow James on Twitter @Botanygeek

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