Gardening Tips
Growing Chili Peppers
Chili (including Bell) peppers belong to the family Solanaceae (nightshade), genus Capsicum (chilies), and
originate in the Americas. A tropical perennial bush, chilies are normally grown as an annual in the
United States.
The word Chili comes from the Nahuatl language of the Aztecs meaning Capsicum fruit. Pepper is actually
a misnomer because these plants are not related to the Black Pepper of India nor the Szechuan Pepper
of Asia.
Chilies were first introduced to Asia by the Portuguese after the year 1500 and have
become a staple part of the diet. Part of their appeal is that the capsaicin heat in the chilies
is anti-microbial, killing bacteria by the millions and making food without refrigeration safer to eat.
There are five domesticated and 23 wild chili species. Three species are found in North American
grocery stores. Capsicum Annuum (a perennial) is the most widely domesticated and includes nearly all
familiar varieties, among them Bell and Jalapeno.
Capsicum Chinense (originating in the Amazon basin) includes Habanero and its even hotter cousins.
Capsicum Frutescens is represented only by Tabasco.
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.
- 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
leave them out eight hours and then plant them late afternoon. Be sure to water the newly planted seedling.
Put chili plants in the ground
when the danger of frost is past. In Oracle, April 15-23 is recommended, but be alert for possible frost
until May 1. 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 similar-sized chilies need the most space.
- Set seedlings in the ground at the same depth that they were in the pot. Do not place their crowns above
soil level. If you think the soil will settle around the plant, place it one-half inch below soil level.
- Shade new seedlings with 50% shade for the first four days to prevent wilting.
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 be white and should not receive direct sun on their sides.
- Avoid planting chilies near beans, any cabbage family member, kohlrabi 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 parsley, basil, carrots, onions and marjoram. Their aromas deter
some insect pests.
Sun and Shade
Provide either 50% shade all day
or full 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
their chilies on the east side of their houses. Also, pests such as flea beetles and leafhoppers are repelled
by shade.
Experiments have shown that seedlings
grown in 50% shade until they were ready to flower had more fruits per plant, a greater mean weight per fruit,
and a much greater total weight of fruits 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 within rainfall
cycles to avoid blossom end rot.
- Simple experiments have revealed that doubling the water applied to Bell chilies doubles their yield -
to a point. If the ground becomes too saturated, it may either suffocate the roots or promote fungal diseases.
Adequate watering increases yields and makes Bell chilies better tasting. Plants with smaller chilies need deep,
less frequent watering.
Use mulch around chili plants
to retain soil moisture. During the hottest days of July and 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
- Most fertilizer recommendations on the Internet are conflicting, sometimes taken from commercial
grower practices. They can be summarized in three steps:
- Before planting, use standard nitrogen-containing fertilizers, such as a 12-12-12.
Nitrogen promotes leaf growth.
- At transplant time, apply one application of high phosphorous fertilizer, such as 10-48-10.
Phosphorous promotes root growth.
- When blossoms are allowed [see Flowering and Pollination below], a 1-2-2 ratio fertilizer
such as 8-16-16 is recommended.
The extra potassium helps flower and fruit development. Excessive nitrogen, on the other hand,
causes chili plants to grow leaves and abort flowers and small pods.
- If the above fertilizers are not available, the home gardener should use compost and a standard tomato
or vegetable fertilizer such as 18-18-21.
- Chilies are not particularly sensitive to soil acidity, but best results are obtained in the 6.0 to
6.8 pH range. Soils in the Oracle, Arizona mountains have tested at pH 7.0, but need amending because of
poor nutritional quality. Do not use ammonium sulfate to acidify the soil because this is a high
nitrogen fertilizer. In general, it is not necessary to change soil pH in Oracle to grow chilies.
In other parts of the desert southwest, especially lower valleys with alkaline soils, a soil acidifier
may be desirable, but do a soil test to be sure.
Flowering and Pollination
Cut off all blossoms
until June 1 - 23 depending on your microclimate. 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 fruits.
In the last half of May temperatures are ideal for fruit set in Oracle.
Day-time temperatures in June become too high on many days, but July brings some relief with cooler
temperatures during the monsoons.
- 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 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 (not a problem in Oracle, Arizona).
- If daytime temperatures exceed 95 degrees, pollen will abort and the fruit set will be reduced.
- Other causes of blossom drop are excessive nitrogen, high winds, and lack of pollination.
Fruit Load
- The maximum weight of fruits 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
- Protect plants from cutworms 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.
- Inspect daily for hornworms and other caterpillars. Pick them off if you find them and dump them in soapy
water or put them in a bird feeder.
- Use insecticidal soap or a Habanero chili/garlic spray to control other insects, including aphids.
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.
- Protect chilies from birds by placing the plant in a cage of chicken wire or bird netting. Most chili plants
need a 2.5' x 2.5' x 3' high cage.
- Chilies are seldom bothered by insects other than aphids until the grasshopper invasion reaches its peak
in Oracle mid-August.
At this time, enclose the entire chili plant in mosquito netting tied around the base of the stem or covering
the cage. Once grasshoppers destroy the leaves of a chili plant, the pods will not ripen further and must be
picked.
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 and Pimento 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 Varieties Ranked by Heat |
| | Thick Flesh | Pod Length | Days to Maturity | Scoville Units |
| Bell | Y | 3-5" | 65-85 | 0 |
| Pimento | Y | 4" | 85+ | 0-100 |
| Mariachi | Y | 4" | 67 | 500-600 |
| Anaheim | N | 6-8" | 80-90 | 500-1000 |
| Paprika | N | 5-9" | 80 | 500-2000 |
| Poblano* | Y | 3-6" | 75-80 | 1000-1500 |
| Cherry Bomb | Y | 2" | 65+ | 3500 |
| Fresno | Y | 2-3" | 75 | 4000 |
| Jalapeno | Y | 2-3" | 75-80 | 4000 |
| Wax | N | 4-6" | 70+ | 5000-10,000 |
| Serrano | N | 1-2" | 85 | 10,000 |
| Cayenne | N | 4-12" | 100 | 30,000 |
| Tabasco | N | 1" | 75 | 30,000 |
| Chiltepin** | N | 0.25" | 75 | 80,000 |
| Thai | N | 1-1.5" | 85 | 80,000 |
| Habanero | N | 2" | 85 | 200,000+ |
| Naga Jolokia | N | 1-3" | 90-120 | 1,000,000 |
* Known as Ancho when dried. ** A wild chili native to Arizona
Environmental Problems
Sunscald
A necrotic or whitish area on the fruit, on the side exposed to afternoon sun, caused by excess sunlight.
The smaller-podded varieties with erect fruits are not as susceptible to sunscald as are the large-podded
varieties, such as Bells and Anaheims. Mature green fruits are the most sensitive. Keep pods shaded by
the plant's leaves or by afternoon screening.
Blossom End Rot
The tissue near the blossom end of pods has a brown discoloration. Spots elongate and become brown
to black, dry and leathery. Blossom-end rot occurs when the plant is unable to take up adequate calcium,
a condition caused by fluctuating soil moisture (drought or over watering), high nitrogen fertilization,
or root pruning during cultivation. It is not caused by low calcium in the soil, but by calcium ion transport
problems in the plant due to fluctuating moisture. Consistent watering at regular, appropriate intervals
prevents and solves the problem.
Pod Drop
Immature pods drop off the plant. This is caused by excessive nitrogen, heat stress, or insufficient water.
Avoid over fertilizing and under watering.
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