Answer: Sounds as though you're growing one of the serrano peppers, which is definitely hot, not sweet. These are great when dried, or used fresh, but should not be substituted for bell peppers in any recipe! You can harvest your hot peppers when they are full sized (which depends upon the true identity of your peppers). Most peppers start out green and then mature to red or purple. They will taste mild in the green stage and get progressively hotter as the color changes, so if you want them as mild as possible, harvest when they're green.
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