Thompson & Morgan Gardening Blog

Having looked at how to keep your chilli plants cool during summer extremes in my last update, I thought I’d flip the focus this time and look at ways of packing extra heat into your chillies.

All chilli varieties fall within their own heat range on the Scoville Heat Scale. If you are new to the scale, the ratings simply represent the number of drops of water needed to dilute the heat of the chilli until you can no longer feel the heat in your mouth. Luckily plant scientists have done this for us so we don’t need to find out the hard way!

Some growers often report a lack of heat in their chillies after harvest, despite growing some of the hotter strains.  Fortunately, there are a few simple tricks you can employ to ensure your chillies top out at the high end of their Scoville range.

A lack of heat is often down to treating the plants too well during the growing season – the heat in a chilli is the plant’s defence mechanism against environmental stress (drought and excessive sunshine/heat) and hungry animals munching on the plants in the wild – interestingly only mammals are affected by the heat in chillies, birds and reptiles can eat them with no ill effect.

Give your chilli plants too much comfort during the growing season and they think there is no need to pack their fruits with heat (sorry to anthropomorphise, I try not to do this when it comes to plants and animals but sometimes it can’t be helped!).

So, to increase the heat and produce fiery chillies the answer is simple – a bit of harsh treatment and tricking them into thinking they are under animal attack.

The first tip to hotter chillies is to allow a good drying period before each watering, even letting the plants wilt for half a day or so before giving them a good drink. I did this earlier in the week, As you can see, having let the plants droop, they soon picked up after a good watering. Don’t do this too many times as it will eventually weaken the plant and have a negative effect, but 3 or 4 times through the season should get the results you want without long term damage to the plant.

Secondly, make the plant feel it is under attack from a hungry herbivore – once a week scrunch a few leaves by hand, even snap the odd side stem, and the plant will think it is being eaten and pack extra heat into its fruit to prevent future attacks.

Thirdly, pump up the heat. Grow two of the same chilli variety in your greenhouse, one at floor level and one as high up on shelving as possible where temperatures will be higher (hot air rises). You’ll notice on eating that the chillies picked from the plant on the floor will be cooler to taste than those picked from the plants on high. Similarly grow one on a windowsill and another in the garden – the garden plant will produce cooler chillies than the one grown in the warmth of the house.

And finally, there is the cheat’s way. I’ve never tried this but I’ve heard that by adding a hot chilli sauce like Tabasco to your watering can, you will transfer the heat to your chillies. You can even try this with sweet peppers and tomatoes and turn them hot. I’d love someone to give this a go on their tomatoes and let me know the results!

Head to our dedicated hub page for more excellent tips, chilli and sweet pepper growing guides, and variety specific advice.

Kris Collins

Kris Collins works as Thompson & Morgan’s quality control manager, making sure customers new and old are kept up to date on the latest plant developments and company news via a wide range of media sources. He trained in London’s Royal Parks and has spent more than a decade writing for UK gardening publications before joining the team at Thompson & Morgan.