You often hear the tip that it’s important not to grow hot peppers (chili peppers) and sweet peppers (bell peppers) in the same vegetable bed. Otherwise, the two will cross pollinate and, at the end of the season, the hot pepper will have lost its burning flavor while the sweet one will become hot as Hades.
And that would seem to make sense: after all, hot peppers and sweet peppers, despite the difference in appearance and in the intensity of their fruits’ taste, are botanically the same plant: Capsicum annuum or other species of Capsicum. (Read Sweet Pepper and Chili Pepper: Two Sides of the Same Coin for more information on the subject.) And plants of the same species will readily cross together.
In fact, though, this tip is mostly false, but with a bit of truth behind it.
No Problem With the First Year’s Harvest
Yes, hot peppers and sweet peppers will cross if planted nearby thanks to bees and other pollinators carrying pollen from one to the other, but that won’t affect the taste of fruit … at least not the first year.
The “genetic mixing” takes place in the seeds that the fruits contain, not in the fruit’s flesh. It will produce the same fruit it was genetically programed to produce, with the same shape, color and taste. And even if the seeds inside a sweet pepper now contain the gene for the production of capsaicin — the compound that gives hot peppers their burning taste —, the seed only carries the gene, it doesn’t express it. Thus, even if you surround a sweet pepper plant with hot peppers, its fruit will always have its usual sweet taste … the first year.
Moreover, any cross pollination will not affect the appearance of the fruit either … the first year that is. The hot pepper will produce a typical hot pepper, usually relatively small and elongated or lumpy, while the sweet pepper will also yield typical sweet pepper fruit, usually large and blocky.
But Watch Out for That Second Generation!
It’s only people who harvest the seeds from their vegetables for the following year (a minority of gardeners) who have to be careful not to plant two varieties of peppers close to each other. If they do, it’s true that there will almost certainly be an exchange of genes that will affect the taste and appearance of the fruit … in the second generation.
The usual recommendation, if you want to harvest seed in order to ensure a certain purity of the lineage, is to isolate different peppers by at least 30 feet (10 m) … and that will likely be impossible to do in an average home vegetable garden or community garden. And even if you could do it, at that distance, there’ll still likely be a bit of mixing, at least occasionally.
Professional seed houses must absolutely ensure perfect varietal purity and thus need to look at an even greater isolation distance: 500 feet (150 m) according to some experts while others recommend up to a mile (1.5 km). The other possibility for seed growers is to isolate peppers in some sort of shelter to which pollinating insects have no access, then to pollinate the flowers manually.
Sadly, even when seeds are produced following official distance isolation guidelines, you’ll occasionally run into a situation when a bee traveled farther than usual and brought foreign pollen to a pure variety. That explains the unpleasant surprise gardeners sometimes experience when the commercially produced seed they paid for doesn’t come “true to type” (doesn’t correspond to its description). Fortunately, that doesn’t occur all that often.
Saving Seed: Always Grow Plants in Isolation
When you are harvesting vegetable seeds of any kind for next year’s crop, no matter which vegetable you grow, be aware that there is always a serious risk of getting plants that don’t come true to type … unless you grow only one variety and are the only person in the entire neighborhood growing the vegetable in question!