Genetics plays the biggest part of how a pepper will taste, but did you know that the way you grow your plants also effects how they taste? We didn't. Last year we grew jalepeño peppers because, well, we love spicy food. We grew them with compost, plenty of water, everything a plant could want. They grew huge! Of course, I was thrilled... that is until we tasted them. They tasted like bell pepper! M-I-L-D MILD. These would never make a good salsa. It was a disappointing harvest.
So we bought new seeds and started researching. Turns out it wasn't the seeds, it was lack of capsaicin. Plants grow in response to their conditions, and although ours probably could have been blazing hot — we were doing it all wrong. Conditions were not right for hot and spicy pepper plants. In the end, I think we just cared for them too much.
If you want to grow hotter jalepeños you just need to care less! Try to follow these simple rules:
Plant in full sun
Peppers love the sun, and they need 6 or more hours of direct exposure to do their best. Any hot, sunny space will do. We actually did this one right, and we grew more than we could use!
Stress those peppers!
Lighten up on the water once the plant begins fruiting. Let the roots dry a bit between watering. Try holding off on fertilizer. If you must fertilize, use a potassium/phosphorus based fertilizer like rock phosphate or kelp. You want just a little stress on the plant. This is key! Capsaicin, the ingredient that gives peppers their heat, is also the plant's defense mechanism. When the plant is stressed it produces more, and you get a spicier pepper.
Leave the peppers on the plant as long as possible, before they start turning red. This allows the pepper to produce as much capsaicin as possible. You want to shoot for picking peppers when they're at their biggest and have started cracking near the stem, but before they're red and passed ripe.
This might explain why our Padrón (a.k.a. shishito) peppers which were planted late, ended up in pots, and often got neglected — were "painful fire" flavored. While our pampered jalepeños were just plain bland. This year we're looking forward to some jalepeño peppers with real heat.