Growing Peppers and Eggplants

Introduction

Peppers (Capsicum annum) and eggplant (Solanum melongena) are popular vegetables and may be grown in home gardens in Colorado. Because they require a long frost-free period to mature fruit, they are usually started in gardens as transplants. Peppers and eggplants can be grown in-ground, in raised beds, and in containers. 

Growing

Plants may be purchased or may be started indoors eight weeks before they are planted into the garden. They are not tolerant of frost, and do not grow well in cool soil. Along the Front Range, both peppers and eggplant can be sown indoors in early April for transplanting into the field on June 1. 

Sow seeds in a prepared potting mix 1/2 inch deep. Seeds will not germinate well in cold soil. Use a heat mat to keep potting mix at 80 degrees F until seedlings emerge. 

As soon as seedlings begin to crowd, transplant the plants into pots or cell packs and grow at 70 degrees by day and 60 degrees at night. Seedlings should receive at least 13 hours of light each day; provide supplemental lighting to ensure health. LED grow lights are energy efficient and are often designed to provide light in the spectrum ideal for plant growth. 

A small greenhouse with automated heat can produce excellent transplants. If you have problems providing the required light and temperatures, purchase good plants prior to transplanting into the garden. The disadvantage of purchased plants is that the variety selection is more limited. 

Because peppers and eggplants produce large fruit on relatively small plants, they must have good growing conditions to produce abundantly. Make sure they receive full sunlight in fertile soil.  

If indicated by a soil test, amend soil with organic matter before planting, or fertilize to provide 1 pound of nitrogen per 1,000 square feet of garden. Work soil amendments and/or fertilizer into the soil prior to setting out the transplants. 

Cover the soil with mulch to suppress weeds, keep fruit off the ground, and reduce surface evaporation, irrigation requirements, and nutrient leaching. Plastic mulches can help warm the soil. “Hot caps” or cloches can protect the transplants from wind and frost and advance the date of transplanting.  

Arrange the plants 1 foot apart in the row, with rows 3 feet apart. This allows 3 square feet per plant. Both peppers and eggplant benefit from protection from high winds and intense sun, which can sunburn the fruit. Maintain a leafy canopy on plants or use a shade cloth to prevent sunscald. 

Pests & Diseases

Peppers and eggplant may be impacted by pests and diseases throughout the growing season. You may encounter flea beetles soon after transplanting. If there are more than four per plant, spray with an insecticide registered for flea beetle control. To deter cutworms, you may want to place cylindrical paper collars around the stems of plants after transplanting into the garden.  

Spider mites, aphids, Colorado potato beetles, thrips, and leafminers are also potential insect pests. Japanese beetles will attack eggplant foliage. Regularly monitoring for signs of insects allows for early effective management. 

Peppers and eggplant can be damaged by soil-borne diseases, foliar fungi, plant viruses, and environmental stress. Fusarium and Phytophthora are the principal soil-borne diseases of eggplant and peppers. They are favored by wet soil and are especially severe where drainage is poor. Treatment options for a home gardener are limited, and infected plants should be removed and destroyed.  Rotate crops to non-hosts to help prevent inoculum build-up in the soil. 

Plants may also be infected with viruses. Symptoms of viral infection include mosaic patterns on leaves and general stunting. A laboratory test can confirm the presence of a virus; infected plants should be removed and destroyed; there is no treatment. Viruses are usually transferred between plants by insects like thrips, but gardeners can also transfer them between plants.  Wash your hands thoroughly before touching other plants after working with a plant you suspect may be infected with a virus or after using tobacco products, which can contain active plant viruses. 

Environmental disorders include poor fruit set and blossom-end rot.  

Peppers and eggplant set fruit best between temperatures are 70 and 90 degrees, when there is sufficient soil moisture, and the bees are active. Pollen production is curtailed when the night temperatures fall below 55 degrees, resulting in a poor fruit set. Blossom-end rot is the result of hyper-local calcium deficiency within plant tissues mediated by water availability; keep the soil uniformly moist to prevent damage to fruits. 

Varieties

Eggplant fruit comes in a variety of shapes and colors that have little to do with the flavor or quality of the fruit. Colors range from black to pink to white and even green; some varieties are striped. Shapes range from elongated sausages to eggs. 

Eggplants grow well in Colorado. Check your favorite seed catalog for interesting and novel varieties. ‘Easter Egg’ produces a white egg-shaped fruit, ‘Black Beauty’ produces the familiar fruit found in most grocery stores, and ‘Oriental Express’ produces an elongated sausage-shaped fruit.

Peppers may be classified as sweet or hot, or by color. Most peppers are either green or yellow-green when immature. When they reach their maximum size, they usually turn red. Because the Colorado growing season is short, large peppers generally are harvested before they turn red, although small peppers generally produce a fair percentage of red fruit. All peppers, including ornamental peppers, are edible, but they are not all palatable. Be careful tasting peppers of unknown hotness. 

Harvesting

It is best to harvest eggplant and peppers with hand pruners to avoid damaging the plants. You can enhance fruit production by harvesting more often. When the fruit reaches an acceptable size, remove it from the plant. If maximum-size fruit is desired, remove all but one or two fruits, so they will receive all the plant’s resources. 

Eggplant flavor or pungency is not influenced by maturity, so fruit may be harvested at any stage of maturity. Older fruits with mature seeds can be tough; harvest young fruits for the best quality. If red peppers are desired, allow the earliest fruit to remain on the plant while harvesting subsequent fruit. Only the early-formed fruit of the large-fruited varieties has a chance to mature before frost. 

Table 1. Pepper types and varieties successful along the Front Range. 

The following pepper types and varieties have done well along the Front Range. 

pepper type	variety
Bells	Predi (large, elongated), Olympus (blocky), Ace (blocky), King Arthur (blocky), Figaro (blocky), Jingle Bells (little), Islander (purple)
Bells, tapered	Ori (green), Fry King (yellow)
Cayenne	Super Cayenne
Cherry	Sweet Cherry, Hot Cherry
Chili	Super Chili (red), Hot Portugal (green), Paper Dragon (yellow), Jalapa (jalapeno), Mosco (mirasol)
Lunchbox	Just Sweet, Eros
Ornamental	Candle Light

Reference: CSU Fact Sheet 7.616