Do your pepper plants have flowers but no peppers?
Hot or Cold Weather: Temperatures – Peppers can be fussy when it comes to temperatures, they don't like it too cold or too hot! Peppers fruit best during daily temperatures between 70-80 °F. (Peppers don't like temperatures below 60˚ F and won't likely produce much if too cold – except for these special cool-weather loving peppers). If it's getting into the 90˚ F temperatures, your peppers may blossom but fruit may not appear if it's too hot for proper fertilization.
Pollination is not occurring: Peppers can be pollinated by the wind, or by hand, or with the help of pollinators. To ensure lots of pollination, attract bumblebees and native bees to your garden by planting native flowering plants and eliminating the use of non-organic chemicals and pesticides. You can also hand pollinate using a small paintbrush or q-tip to spread pollen from bloom to bloom.
Too much nitrogen: If your pepper plants are lush with lots of leaves but you're not seeing any fruit, you may be over-fertilizing them with nitrogen. Too much nitrogen can compromise flower and fruit production, as the plant will put all of it's energy into foliage. Once the plant is a good size and starts to flower, reduce high-nitrogen fertilizers. We like to use use homemade compost for the best harvest, which has a healthy balance of phosphorous and potassium as well as nitrogen.