Gardening in Tucson
and Southeastern Arizona

Overview

Selecting Seedlings and When to Plant

• At a nursery, choose large, robust seedlings that do not yet have fruit. While seedlings without blossoms are often recommended as the best choice, plants with blossoms but no fruit are okay as long as you snip off the blossoms as soon as you get home. The plant should still be in a growth mode and not switched to fruit production mode.
• If large Bell-type peppers are desired, consider Poblano (sometimes mistakenly labeled Ancho) chilies instead. Bells often do not set fruit when temperatures are over 90°F unless they have Numex or TAM in their names. The Numex and TAM varieties were bred for high temperature conditions. Bell peppers may begin to set fruit once the weather is cool.
• Harden seedlings off before planting by leaving them out during the day, and then bring them inside next to a sunny window. One hour outside the first day, two hours the second, four hours the third. On the fourth day plant them in the morning. Be sure to water the newly planted seedlings.
• Put chili plants in the ground when the danger of frost is past. In case a late frost is predicted, be prepared to cover plants and/or surround each one with Wall-O'Water or plastic bottles filled with water. Chilies are badly damaged or killed by frost.

Chili Plant Location

• Place chilies in well-draining soil in raised garden beds or pots with bottoms not resting in saucers. Chilies do not like wet toes.
• Do not crowd chilies. They should be 18-24" apart in rows 24-36" apart, depending on pod size. In other words, 3-6 square feet is needed per chili plant. The larger the pod produced by the plant, the more space is required. Bell and Poblano chilies need 6 square feet of space for each plant.
• Set seedlings in the ground at the same depth that they were in the pot. Do not place their crowns (stem-root junction) above soil level.
• Shade new seedlings with 50% shade for the first four days to prevent wilting. After that, provide full sun.
• Rotate plants yearly so that the same garden bed does not see nightshade family members more than one year in four. Nightshade family members include tomato, chili, eggplant, potato, sacred datura and petunia. This will discourage the build-up of soil-borne diseases common to nightshades.
• Use containers only for plants that produce small chili pods such as Chiltepins and ornamentals. The roots of large pod plants need more space than a container can provide. If using containers, the pots should not receive direct sun on their sides.
• Avoid planting chilies near beans, any cabbage family member, or fennel. The roots of these plants produce chemicals in the soil that stunt or harm chilies or vigorously compete for the same nutrients.
• Good nearby companions for chilies are basil, carrot, geraniums, onion, marjoram, oregano, and parsley. Their aromas deter some insect pests. Allow some of the parsley to flower. This will attract hoverflies which prey on aphids. Because aphids prefer them, geraniums in pots are used as a trap crop, sacrificed to protect chilies and other edibles.

Sun and Shade

• Provide full sun in the morning and 50% afternoon shade. Chilies need 6 hours or more of sunlight. However, always provide at least 50% afternoon shade in Arizona. Many Phoenix growers have good success growing chilies on the east side of their houses.
• Experiments have shown that seedlings grown in 50% shade until they were ready to flower had more fruit per plant, a greater mean weight per fruit, and a much greater total weight of fruit per plant. Therefore, chili plants purchased from nursery greenhouses, where the light conditions are lower, will yield more fruit than plants directly-seeded in full sun.

Watering

• Gardeners should adjust the frequency and amount of watering to rainfall cycles. Do not water if there has just been a heavy downpour. Make sure the rainfall has penetrated deeply and not just wet the surface. A rain gauge can help with this.
• Water consistently to avoid blossom end rot.
• Use mulch around chili plants to retain soil moisture. During the hottest days of June through August, many plants experience water loss by transpiration [evaporation through their leaves], no matter how wet the ground is. The results are wilting, flower drop, and sometimes even fruit drop. The simplest method of fighting transpiration water loss is to increase the humidity around the plants by wetting thick layers of mulch and/or by growing in 30-50% shade. Chilies are tropical and love high humidity.
• For chili plants in containers, use a wider than normal saucer filled with small gravel to the brim. Place the pot on top of the gravel and keep water in the saucer at all times to provide humidity around the leaves. The gravel will keep water from entering the pot from the bottom.
• Water soil and mulch, not leaves, to cut down on bacterial and fungal diseases.

Fertilizing and Soil Acidity

Flowering and Pollination

• Cut off all blossoms for the first six weeks after planting. The later the better, but the date depends on days to maturity of the chili variety and first frost date. This forces chili plants to devote their energy to producing more leaves and roots rather than fruit production, resulting in larger plants that produce more market-sized fruit.
• Chilies are usually considered to be self-pollinating. A finger tap at the base of the flower will cause pollination. They cross-pollinate easily, so seeds from a garden with multiple Capsicum Annuum varieties often produce hybrid plants with more vigor the following year.
• The key factor affecting fruit set is night temperature, which ideally should be between 65 and 80 degrees F. Fruit will not set when the temperature is above 86 degrees at night because of excessive transpiration, which causes blossom drop.
• Other causes of blossom drop are excessive nitrogen, high winds, and lack of pollination.
• If daytime temperatures exceed 95 degrees, pollen will abort and fruit set will be reduced.
• Unlike most chilies, Bell peppers may not set fruit at all during the summer because of their sensitivity to high daytime temperatures.

Fruit Load

• The maximum weight of fruit that a fruiting plant can bear is known as its fruit load. The fruit load of each chili plant is dependent on stem size, amount of foliage, and the extent of the root system.
• When a chili plant achieves its fruit load, it ceases flowering. Thus a plant will stop producing fruit even though there may be a month or more left in the growing season.
• Increase the yield of chili plants by picking some pods in their largest immature green form. The plant will continue flowering and setting fruit throughout the remainder of the season, and the total weight of pods produced by the plant will be greater. For some early-ripening, quick-to-red chili varieties, it may be possible to pick chilies on the first day of turning red without alerting the plant that it has achieved its goal of bearing mature chilies.

Harvest

• Remove chili pods from the plant with a sharp pair of garden pruners or scissors. Avoid pulling or breaking fruit from the plant, because chili branches are easily damaged.
• Chilies can be harvested at any time after the fruit have reached the desired size.
• Flavor, except for sweetness, is not influenced by maturity. Each variety of chili has its own set of aromatic substances that give it a unique flavor. Some have more flavor compounds than others.
• Allowing fruit to ripen on the plant will produce a sweeter taste and higher vitamin content, but lower total pod production.
• Ripen green chilies to a red color after picking by placing them at the bottom of a fruit-ripening bowl with apples on top of them. Ethylene gas from the apples causes quick ripening.

Weeds

• Chilies do not compete well with weeds. More than 150 types of weeds harbor insect-transmitted viruses that can harm chilies. Weeds also steal nutrients and moisture from the soil.
• Remove weeds by hand. Avoid tilling the soil. Cutting roots causes slower plant growth, reduced pod production and Blossom End Rot.
• Herbicides should never be used.

Pests

• Cutworms can be deterred by placing a paper collar or a 6-inch plastic pot with the bottom cut out around the stem and driven into the dirt about one-half inch.
• Hornworms and other caterpillars need daily inspection. Pick them off if you find them and dump them in soapy water or put them in a bird feeder.
• For Aphids and other insects, use insecticidal soap or a Habanero chili/garlic spray. Avoid pyrethrum insecticides because they can harm the plant. Aphids can also be washed off with a stream of water from a small garden sprayer. Lacewing insect larvae (ant lions) and Ladybugs can also be used to kill aphids, but avoid all insecticides if they are present.
• Flea beetles eat small round holes in leaves. There are many species of flea beetle, with potato flea beetles and tobacco flea beetles being the likely culprit for chilies. If you wish to avoid weekly use of insecticides like Sevin, organic controls consist of yellow and white sticky traps and diatomaceous earth sprinkled as a dry powder on the plant. Once insects destroy the leaves of a chili plant, the pods will not ripen further and must be picked and placed in a fruit-ripening bowl.
• Grasshoppers will eat the flesh of mildly hot chilies such as Mexibell when just the shoulders of the fruit are red. One defense against grasshoppers is to spray the fruit with garlic-pepper solution before the grasshopper has a chance to eat it. This must be re-applied after every rain. A grasshopper control product that contains Nosema locustae protozoa can be purchased online, for use in early summer, on fields surrounding the garden.
• Birds can be excluded by a cage of chicken wire or bird netting. Most chili plants need a 2.5' x 2.5' x 3' high cage.

Pungency

• Capsaicin, the chemical "heat" in chili, is often measured by Scoville units, originally the proportion of water used to dilute one unit of chili pulp until no heat was detected.
• Chili pods have evolved to be consumed by birds, not mammals. The heat that bothers mammals does not affect birds because they have no sensory receptors for capsaicin. Chili seeds pass through bird digestive tracts unscathed but are often destroyed by mammalian digestive tracts.
• Bell chilies always remain mild, even when flesh ripens to red.
• Mature pods of the non-Bell chilies are more pungent than immature pods. Generally speaking, stressing chili plants increases their pungency. This includes insufficient water and high temperatures during fruit ripening.
• The most pungent part of the pod is the placental tissue, or cross wall, which holds the seeds and produces capsaicin. The pod is most pungent at the stem end and less so at the apex. The seeds themselves are not very hot but may pick up capsaicin during processing.

Chili Plant Problems