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Growing Peppers in Minnesota

Updated: Apr 13, 2021

There are sweet peppers and hot peppers. A volatile compound called capsaicin causes the heat in hot peppers. The capsaicin level is measured in Scoville units, the measure of the dilution of pepper juice needed to still taste the heat in peppers. The common sweet pepper has a Scoville rating of zero, while the current record holder (Dragon’s Breath pepper) clocks in at 2.48 million (stronger than military grade pepper spray). Take care to wear plastic gloves when handling hot peppers, AND DON’T TOUCH ANY PART OF YOUR BODY. Work in a well-ventilated space. Capsaicin can irritate the skin, mucous membranes and can cause serious eye damage. Keep hot peppers away from children and pets.

Early spring, before the rush, is a great time to get your soil tested. Follow instructions at the University of Minnesota Soil Testing Laboratory. The results will guide you in the fertilizer requirements you need for the best peppers. The best pH for peppers is about 6.5 to 7.0, but peppers do not seem especially picky about soil pH. Twin Cities soils generally have more than enough phosphorus, and often a low phosphorus or no phosphorus fertilizer is recommended. Calcium is also abundant in our local soils. Too much nitrogen produces lush green leaves and less fruit. A few weeks before planting, spade in generous amounts of finished compost or well-rotted manure.

Peppers are in the Solanaceae family which includes tomatoes, peppers, eggplant, potatoes, and tomatillos. The members of this family tend to share the same disease and insect problems. For at least 3-4 years, peppers should not be planted in a spot where these other plants grew. Grafted peppers on disease resistant rootstock can overcome this problem, but mail-order costs approach $10.00 per plant.

If you grow your own peppers, or if you get plants by mail order, you should prepare your plants for the outdoors. You would not run a marathon without proper training. Likewise, peppers need to be conditioned before they brave the winds, rain, and sun of the garden. In a process called hardening off, young plants (6-weeks old) are left outdoors for a couple hours in a protected place. Then over a 10-14-day period, the plants are left outside for longer and longer times. Water a bit less during this period, but don’t let the plants wilt. If night temperatures drop below 50° F, bring the plants indoors. You now have tough plants that should do well in the garden.

In the nursery, choose stocky plants up to 12 inches tall with 3 to 5 sets of closely spaced leaves, with at least pencil width stems, and no discoloration or disease on the leaves. Do not choose a plant with flowers or fruit. If you do end up with such a plant, before planting pinch off the flowers or fruit and let the new transplant direct its energy into producing good roots and leaves. Additional success is found if you choose “widely adapted”, “cold tolerant”, or “recommended for northern gardens” varieties.

Remember, peppers need to be transplanted into warm soil. Rather than rushing to plant and risk poor growth, wait two weeks after planting tomatoes and until the soil really warms up. A pepper in cold soil will sulk, may become stunted, and may never catch up. Night time temperatures should consistently be above 55 ° F. Choose a spot that has \ full sunshine, or a minimum of 6-8 hours of direct sunlight daily. Black plastic is often placed over the soil for a few weeks to warm up the planting soil before planting. If you plan to leave the plastic for the season, drip irrigation or weeper hose should be installed before placing plastic. The black plastic will keep the soil warm improving pepper growth, reduce competition from weeds, and will help to keep the soil moist. The soil in raised beds tends to warm up sooner in the early spring.

Transplant in the evening or on a cloudy day to minimize wilting. Unlike tomatoes which can be planted deeply and will form new roots along the stems, peppers need to be planted at the same level as in the pot. Dig a 3-4-inch hole, moisten the seedling, and plant it. Firm the soil around the plant. Add a protective paper collar around the stem to discourage cutworms. Water the plant with a weak starter fertilizer solution or diluted liquid fertilizer, giving a boost to the young plant. Space plants at least 18 inches apart in rows 30 inches apart to provide plenty of air circulation which will quickly dry plants and reduce disease conditions. Add a stake and loosely tie or use a commercial 3- or 4-ring tomato cage, which is ideal for supporting peppers. This will support the top-heavy production of pepper plants. Fertilize the soil with a slow release fertilizer, a commercial granular fertilizer, or an organic fertilizer following your soil test recommendations and the manufacturer’s directions. Another dose of fertilizer, with a higher potassium value, will be needed when the plants start to bloom.

Hot caps, cloches, Wall o’ Waters, Cozy Coats, cut-milk jugs, clear plastic tunnels, or floating row covers suspended on low hoops can provide additional warmth early in the season. Remove the coverings on warm days. Remove the protective devices before the temperature reaches 80° to prevent overheating. Removing the devices also allows bees and other pollinators to access the fruit.

Peppers require 1-2” of water each week. This is not a light sprinkle many times a week. It should be a deep watering. Sparse watering will cause the plants to develop shallow roots and will result in decreased fruit quality. The plant itself is weakened and becomes more susceptible to drought damage. Place water at the base of the plant. Installing an inexpensive drip irrigation system or soaker hose is ideal. Overhead watering wets leaves and creates a humid environment which encourages plant diseases to develop. Try to water early in the day, so that the pepper plants have time to dry off in the sun. An inexpensive rain gauge is a good garden tool. If it rains, you can ease off on the watering. If the soil is sandy, if it is very hot, or if there is a drought you may have to water more frequently than once a week.

Try for that Goldilocks condition when watering: not too wet, not too dry, but just moist. We want damp sponge conditions around the roots, not a bathtub full of water. Use your index finger to push into the soil near the plant and test for watering needs. Too much water can result in fungal disease and root rot.

Peppers, as well as tomatoes, can suffer from a condition called blossom end rot. The end of the fruit blackens and starts to rot, due to a calcium deficiency. Our soils in the Twin Cities have plenty of calcium; but if there is inconsistent watering calcium cannot be transported adequately to the end of the fruit. Blossom end rot sets in. The prevention for blossom end rot in both tomatoes and peppers is good watering practices.

When weeding, remember that peppers have a shallow root system. Shallow scraping with a hoe will remove most weeds. If you choose not to use black plastic, an organic mulch a 3-4 inches deep may be applied around the plant. Wait until June when the soil really warms up to apply the organic mulch, because it tends to keep the ground a bit cooler. The mulch will help preserve ground moisture, discourage weeds, moderate ground temperature, and as it decomposes it will provide organic material to the soil. The mulch can be weed-free straw, herbicide-free grass clippings, or chopped leaves. If using chopped leaves, be careful not to include walnut tree leaves. Walnut trees produce a toxin that can kill a pepper plant.

Scout your pepper crop frequently for growth, disease, insect, or watering problems. Correct the problem immediately.

Use hand held pruners or a very sharp knife to harvest your crop. The stems of peppers can be very brittle, and you want to avoid snapping off a nice branch of peppers that aren’t ready to be harvested. To keep the harvest going, pick all peppers as they mature. If an early frost threatens, have protective blankets ready to protect your plants and to extend your harvest.

Penn State Extension has an excellent article on Growing Peppers in Containers.

The University of Minnesota Extension article, Growing Peppers in Home Gardens,

has more information on peppers in gardens. Happy Pepper Gardening,

Joe Baltrukonis


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