Why are some jalapeños hot and others not?
While the jalapeño heat is contained in the seeds and veins (or placenta) of the pepper, jalapeño pepper heat levels do vary depending on many factors such as age of the pepper, how many overall seeds are within the pepper, when and where it was grown (hotter climates produces hotter peppers).
A jalapeño pepper can vary in heat level from between 2,500 and 8,000 Scoville units. If you find that a chile pepper is too hot, you can always reduce the heat by removing the seeds and veins but you can’t make them hotter without dumping habanero powder over them. Also, the red jalapeño peppers tend to be sweeter and not necessarily hotter. Jalapeños will turn red the longer they are on the vine and eventually fall off.
So how can we tell without cutting open the peppers and tasting them? It seems that jalapeño peppers get hotter as they get older and the older they get, they change in appearance. When young, they are smooth, uniformly green and less hot but as they get older they start to develop striations or lines akin to stretch marks in the outer skin. You’ll also start seeing little white lines and white flecks in the skin. Peppers with a wilted or browned stem are the hottest.
For those that grow their own chiles note that the heat of the pepper is largely determined by soil moisture. As the soil dries, the chiles release capsaicin as a defence mechanism. So, if you want hotter chiles, go easier on the watering and let the soil dry.
Also note that there are different varieties of jalapeños. If you like a hot jalapeño, try Biker Billy, Early and Mitla varieties. For a milder version, we suggest Delicas, Senorita or Tam.