Pepper Secrets

By Steve Reiners, Professor and Chair, Horticulture Section, School of Integrative Plant Science, Cornell University, Cornell AgriTech.
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June 2, 2021

Do you have a problem growing peppers? Maybe great success one summer and frustration the next? It’s a complaint I often hear from gardeners. And since we’re getting to pepper planting time, let’s review pepper protocols.

First, let’s start with pepper varieties. There are many different types of peppers to choose from. Lots of colors and shapes. Perhaps of greatest interest, the level of heat or spiciness in the fruit. The heat comes from capsaicin, a compound found within the fruit of some peppers. We have a rating system for pepper heat, using ‘Scoville Heat Units,” named after a Connecticut pharmacist, Wilbur Scoville, who developed the scale in 1912.

The Scoville Heat Units are based on the level of capsaicin in the pepper. A sweet bell pepper has 0 units. The hottest pepper on the scale is the Carolina Reaper, coming in at more than 1.5 million units. The table below provides a listing of pepper heat.

Scoville Heat Units for commonly grown peppers

Pepper Type

Scoville Heat Units















Thai Chiles


Scotch Bonnet



150,000- 350,000

Ghost Chiles


Carolina Reaper


Looking at this chart gives you an idea of the type of peppers you may want to grow. But it also gives me a chance to correct a common misconception. If you plant a sweet bell pepper next to a habanero, you will not get hot bell peppers. What you could get are seeds within the bell pepper that have the genetics that could produce hot bells if you saved the seed to replant. The cross, and the heat, will not be seen in the fruit this year.

Scientists think peppers evolved to produce capsaicin to keep animals from eating the fruit. In fact, capsaicin is often used in animal repellants. Interestingly, birds are not bothered by capsaicin and can eat the fruit without any ill effects. This ensures that the seed will be spread as far as the birds will fly.

Capsaicin is found only in the fruit and not in stems or leaves. Within the fruit, the capsaicin is higher near the seeds, and the seeds tend to be near the stem end of the fruit. You can impress your friends by biting the blossom end where the heat is less. But have some milk or bread handy to minimize the burn.

Peppers of course are a warm-season crop. They cannot be planted outside until after the last frost and the soil has warmed up. Memorial Day is usually a good time to plant here in Ithaca.

If purchasing your peppers from a greenhouse or garden center, you won’t have nearly as many choices as what you will have with tomatoes. Your decision will likely be based on whether you want a hot type or sweet, perhaps the shape (bell or tapered), and the mature color. Most pepper plants are similar in size so no need to worry about determinate or indeterminate plants.

Speaking of pepper color, most peppers typically start off as green just like tomatoes. As they ripen, they develop their color, often red, orange, or yellow. A green fruit is fine to eat but it is immature. A colored fruit will be sweeter and likely hotter than the immature fruit.

The biggest problem that most gardeners have is out of their control, and that’s the air temperature. Hot days over 90F and nights that stay above 75F will cause blossoms to drop and a loss of potential fruit. It’s extremely important to keep the soil well irrigated and not add to the stress the plant experiences. On the positive side, stressed peppers usually have more capsaicin and are hotter than those growing under ideal conditions.

Although we don’t need elaborate staking/caging methods to keep pepper plants upright, a little support can help. A plant with a full load can easily topple over or have branches break from the weight. I usually only have a few peppers in my garden, so I place a one to two foot stake next to each plant when young. I don’t tie it to the stake. The plant leans on the stake and just that little bit of support keeps the plants upright.

If growing a row of peppers, you can try what commercial growers do. Take that stake and place one every eight feet. While the plants are still young, run a single line of string from stake to stake. The plants will then be supported by the string.

Finally, take care when harvesting the fruit. Unlike tomatoes that usually pull off the vine easily, pepper fruit are well attached. Simply grabbing a fruit and pulling it off often breaks off entire branches. That’s bad for a couple of reasons. Often small, immature peppers come off with it. In addition, if branches are suddenly removed, young fruit they were shading will suddenly be exposed to the sun. That can lead to sun scald and loss of fruit.

The best way to harvest peppers is with a pruning shear or scissors. Cut the fruit’s stem carefully and remove the fruit.

In the garden this week

Beginner gardeners are often confused as to whether they should remove flowers from tomatoes, peppers and eggplants when setting their transplants in their beds. If the plant has flowers, leave them alone. If the plant has small fruit, those can be removed. Developing fruit require lots of the plant’s resources. For the first few weeks, you want the plant to grow strong stems and lots of leaves that will photosynthesize and support lots of fruit. Fruit on a small plant won’t allow that to happen. Yes, you will get some small, early fruit but at the expense of a big harvest later. Flowers don’t cause the same resource drain as fruit.