Although bell peppers (Capsicum annuum) are hardy in U.S. Department of Agriculture zones 1 through 11 -- which means they can grow virtually anywhere -- they need at least 65 days of full sun and temperatures that remain above 60 degrees Fahrenheit after planting to begin producing. Peppers can be green, red, yellow or orange, depending on the variant, and pruning the plants early in the season improves their quality. Pruning late in the growing season, on the other hand, speeds up the ripening of the peppers that haven't been harvested.
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Growing Bell Peppers
If you don't want to plant starts, growing bell peppers from seed is easy, although it's important to keep them warm until the seedlings are ready for transplanting. They do well in a conventional potting mix, which you should keep moist and well-drained. Although pepper plants may start producing fruit in as little as 65 days, the main harvest usually occurs from 100 to 150 days after transplanting.
Start seeds from eight to 10 weeks before the last frost in a space with a minimum temperature of 75 degrees F. Sow three seeds per pot, and remove the weakest seedling when all emerge. The two remaining plants protect each other and will probably produce more in tandem than each plant would separately.
About 10 days before transplanting the seedlings, when they are 6 to 8 inches tall, harden them off by decreasing the daytime temperature to 60 to 65 degrees Fahrenheit for a week.
Peppers prefer slight acidic to neutral soil, with a pH between 6.2 and 7, although they will grow in slightly alkaline soil with a pH as high as 7.5. The soil temperature must be 75 degrees F or higher -- warm up the soil with black plastic if the nights are still cold. Before transplanting the starts, work a 3- to 5-inch layer of compost and fertilizer into the soil to help it retain moisture.
Space the holes from 18 to 24 inches apart, and fill each one with a teaspoon of fertilizer and three matchsticks to provide sulfur, which the plants like. The mature plants will benefit from support stakes, especially when heavy with fruit, and it's best to place the stakes when planting them.
Fertilizing and Watering
The best time to fertilize pepper plants is when you transplant them. Just before you do, work the fertilizer into the soil along with compost; use 5-10-10 fertilizer at a rate of 3 pounds per 100 square feet. Fertilize again when fruits begin to appear, but do it cautiously, using plenty of water to saturate the soil and prevent nitrogen build-up that can kill the plants.
Pepper plants need 1 to 2 inches of water every week, but because they are heat-sensitive, you should water them daily if the days are hot and dry. Mulching with straw helps the plants retain moisture and is especially beneficial in hot climates.
Growing plants may be attacked by aphids and thrips, especially in hot weather when weeds begin to dry out. You can often dislodge them with a spray of cold water on the leaves; if that doesn't work, spray the leaves with insecticidal soap. Soon after transplanting, the leaves may be also be attacked by flea beetles, which eat shot-like holes in the leaves. Control them with a spray made by combining 2 parts alcohol, 5 parts water and a tablespoon of liquid soap.
If you find caterpillars or weevils on the leaves, pick them off by hand. Mosaic viruses can mottle the leaves, turning them shades of yellow, white and light green. There's no cure for this other than to destroy infected plants.
Pruning Pepper Plants
Pruning the plants is beneficial at two times during the growing season. Early in the season, it helps improve fruit quality, but contrary to myth, it doesn't necessarily increase the yield, and may actually reduce it. Pruning late in the season focuses the energy of the plant on any remaining fruit and hastens the ripening process.
Early-season pruning should be done after the plant has reached a foot in height and before fruit has started to appear. Note how the branches grow in pairs, forming a "Y" shape from the point of origination. Choose the smaller of the branches at each junction and cut it off with clippers sterilized with alcohol to prevent the spread of disease.
Limit pruning to branches that are undersized and lack vigor -- you don't want to thin the foliage too much, especially in hot sunny climates, or it may burn.
It's easier to decide which parts of the plant to prune late in the season -- basically any wilting or browning growth can go, leaving only healthy stems, leaves and unharvested fruit.