Probably variety. There are many varieties of cayenne, some are hot(100,000 scu) others rather mild.

I agree with Farmer..if you have a healthy plant and plenty of pods it most likely is a milder variety.

I have Ristra Cayenne they taste sweet at the lower 1/2 and about jalapeno heat in the upper 1/2 very mild. Will not grow again because it's too mild for me and flavor was not so good compared to the Ghost.

Agree it just may very well be the variety.

All peppers tend to be hotter at the top. Capsaicin is produced and found in the placental partition (the white cross-wall and veins) of the pod, not in the seeds as is commonly believed. The seeds become pungent through contact with the placenta. The majority of the placental tissue is localized at the top of the pepper, and that's where you'll notice the most heat if you pay attention.

I hope this information will enhance your chili-eating experience. :0)

Your pepper plant may just not be a spicy variety (i.e., for genetic reasons), as someone else suggested above. That said, there are a few things you can do to get spicier pods. Here's some information from Cross-Country Nurseries webiste:

The heat level of chiles is in direct relation with the amount of water that the plant receives as the pepper fruits are forming. Milder than usual chiles are found on plants that have been given an excess of water, pampered plants tend to produce wimpy chiles! This also will happen with plants grown in cool and wet areas, such as Washington and Maine. Plants grown in Florida and Arizona however tend to produce chiles that are quite hot, due to the area's dry and hot climate. If you want to produce extra hot chiles, stress the plants by withholding water, even letting them wilt. Do this only on established plants, not to very young transplants that are just getting started. To revive them from the wilt stage, water like normal, do not over-water at this time or you may drown the plant, and kill it.

maple grove gave some very good advice.

I let my plants wilt before watering them. It makes the peppers hotter, and it the best way to be sure they need water.

Thank you everyone. Maple Grove, thank you for that great advice. I suspected it was because I kept it too moist/hydrated. I'll try again next year with less water.

How long should I allow it to wilt before watering it? A few days? Weeks?

Kendra,

Once your plant starts to wilt you should provide it with water right away. I suspect there's a fine line between withholding water to increase pungency, and damaging the plant if it dries out too much! Here's some more information, this time from Dave DeWitt & Paul W. Bosland's "The Complete Chile Pepper Book":

About 50% of the pungency is genetic and about 50% is environmental. Generally speaking, stressing pepper plants increases their pungency. Both restricting water and overwatering (a dangerous practice) will increase the amount of capsaicin in the pods. Restrict the water until the plants just start to wilt, then water them slightly to perk them back up. Do this several times throughout the growing season and the pods should be hotter. The pungency is also increased when the fruit ripens at higher temperatures. In fact, the pods of New Mexican varieties ripening at temperatures between 86 and 95 *F have twice as much capsaicin as those ripening at 59 to 72 *F. Applying nitrogen after fruit set can lower capsaicin levels.

I water thoroughly while the plant is forming pods so that they achieve maximum size,
but I hold off on the water for a day or two before I intend to harvest, in order
to concentrate the sugars and capcaicin.

Josh

If there are other types of peppers growing near it, it is possible that it may have been cross fertilized with some of the others like bell peppers and that could be why it is more mild. Also the longer you leave it on the plant the hotter it will be.

Plants do not confer heat or mildness through mere proximity to other plants. Only growing out the crossed seeds will result in changed genetics.

Josh

I know my response is waaaay late but in case someone comes accross this thread I will say and I’m surprised nobody mectioned it but cayenne peppers produce a round of peppers in the summer and then the plant makes a comeback in the fall and produces a second round of peppers and those are always 3-4 times hotter! Mine are that way every single time I have grown them no matter how I water them.