Chilli – Growing Guide

Overview

• Name: Chilli (Chili Pepper, Hot Pepper)
• Botanical Name: Capsicum spp.
• Plant Family: Solanaceae (Nightshade Family)
• Native to: Central and South America

Description

Chillies are annual or perennial plants from the genus Capsicum, which includes several species:

• Capsicum annuum: Jalapeños, cayennes, and bell peppers (also known as sweet peppers).
• Capsicum frutescens: Tabasco and piri piri.
• Capsicum chinense: Habaneros and Scotch bonnet.
• Capsicum pubescens: Rocoto and Manzano.
• Capsicum baccatum: Aji peppers.

While most peppers are spicy, bell peppers (a variety of C. annuum) lack the heat characteristic of other Capsicum species.

Chilli plants exhibit diverse growth habits, ranging from herbaceous to shrub-like forms, with typical heights between 0.5 and 1.5 meters (1.6 to 5 feet). Some varieties, like the Zimbabwe Birdseye, grow as small as 30 cm (12 inches), while others, like the Rocoto Tree Chilli, can exceed 2 meters (6 feet).

In temperate climates, chillies are grown as annuals, completing their life cycle in one season. In tropical and subtropical regions, they can act as perennials, producing fruit for several years.

The plants have erect, branching structures with green to brown stems. Leaves are usually dark green, smooth, and either ovate (egg-shaped) or lanceolate (pointed), with entire (straight) margins, arranged alternately along the branches.

Chilli flowers are small, star-shaped, and typically have five petals, ranging in colour from white to purple or yellow, depending on the species. These self-pollinating flowers appear in clusters and bloom during the summer, eventually producing the chilli fruits used for food, medicine, and spices.

Chilli fruits are botanically non-pulpy berries with large air pockets and numerous flat, yellowish seeds. They vary greatly in size, shape, colour, and heat level, from small round berries to long slender pods, in colours such as green, red, yellow, purple, orange, and black. The bright red color is the most common in many varieties, and is due to carotenoid compounds.

The heat of chillies is measured in Scoville Heat Units (SHU), based on the concentration of capsaicin, the compound responsible for their spiciness. This heat ranges from zero in bell peppers to over 2 million SHU in the Carolina Reaper (C. chinense).

Chillies are believed to have originated in the Americas, with Capsicum annuum likely native to Mexico, and other species originating in different parts of South America. Today, chillies are cultivated worldwide for their culinary, medicinal, and ornamental uses. appeal.

For additional information, see article – A Gardener’s Guide to Identifying Different Chilli Species

Interesting Facts

1. Chillies were domesticated over 6,000 years ago in Central and South America. Ancient civilizations, like the Aztecs and Incas, first cultivated chillies for food, medicine, and rituals, making them an essential part of their culture.
2. The word “chilli” comes from the Nahuatl word chīlli, the Aztec language, referring to spicy peppers. Spanish explorers adopted the term, spreading it across Europe. The word evolved into different forms, like “chilli” in British English and “chili” in American English.
3. The compound capsaicin, which gives chillies their heat, is used not only in cooking but also in medical products for pain relief. It works by desensitizing nerve receptors and is commonly found in topical creams and patches for conditions like arthritis and neuropathic pain.
4. Chillies are rich in vitamins A and C, which boost the immune system. These antioxidants protect the body from free radicals, supporting overall health and making chillies a valuable addition to a balanced diet.
5. The Scoville Scale, named creator Wilbur Scoville, was developed in 1912 to measure the spiciness of chilli peppers in Scoville Heat Units (SHU), indicating the amount of capsaicin present. Capsaicin levels are now measured using advanced methods like high-performance liquid chromatography, providing more accurate spiciness ratings.
6. Super hot chillies can exceed 1 million Scoville Heat Units (SHU), offering intense spiciness. These chillies are prized for adding fiery heat to dishes and are used in crafting gourmet hot sauces and other spicy delicacies.
7. Capsaicin affects mammals but not birds, as birds lack the pain receptors sensitive to capsaicin. This evolutionary adaptation allows birds to spread chilli seeds widely without harm, while mammals are deterred by the spiciness.
8. Pepper spray, used for self-defense and riot control, is derived from chilli peppers. It contains oleoresin capsicum (OC), with a much higher concentration of capsaicin than found in food, causing intense burning sensations, temporary blindness, and difficulty breathing, making it an effective non-lethal deterrent for incapacitating aggressors.

To learn how to make a chilli-based rat and mouse repellent that also works on other pest and nuisance mammals such as deer, elk, rabbits, and squirrels, see article – Spice Up Your Rodent Defense With Potent Chili Capsaicin-Based Repellent Sprays

Basic Growing Information

Chillies are a warm-season crop that grow best at temperatures between 18-30°C (65–86°F) during the day and 16-21°C (60-70°F) during the night. They generally require a long growing season, and grow very slowly during cool periods, so the best time for planting is after the soil has warmed to 18°C (65°F) or more, in late spring or early summer after the last frost.

To set fruit, chiles need daytime temperatures between 18-27°C (65-80°F) and nighttime temperatures above 13°C (55°F). They won’t set fruit if nighttime temperatures stay above 30°C (86°F).

Since they originate from warmer climates, chilli plants are very sensitive to cold. Temperatures below 15°C (59°F) can stunt their growth and delay flowering. If temperatures drop below 10-13°C (50-55°F), flowers may abort, or fruits may become misshapen.

In cooler climates, or regions with shorter growing seasons, starting chilli seeds indoors 8-10 weeks before the last frost date and transplanting them outdoors when the soil has sufficiently warmed can extend growing time and improve the chances of producing a decent harvest.

Chillies also prefer well-drained, fertile soil and regular watering, but dislike waterlogged soils, which can lead to root rot.

• Sun Requirements: Full sun
• Water Requirements: Moderate
• Soil Types and Properties: Well-draining, fertile soil
• Soil pH: 6.0 – 7.0
• Pot Size for Container Growing: 25-30cm pot

Planting

• Best Time to Plant:
  • Climates with freezing winters: Start seeds indoors about 8–10 weeks before the last frost date. Transplant outdoors when the danger of frost has passed and temperatures consistently exceed 18°C (65°F).
  • Climates with milder winters: Can be sown directly outdoors after all danger of frost has passed.

Note: Check gardening calendars for the best planting times in your location

• Spacing: Plant seedlings 30–45 cm (12–18 in) apart and 60–75 cm (24–30 in) between rows.
• Seed Sowing Method: Start indoors in seed trays or small pots.
• Seed Sowing Depth: 5mm (¼ inch) deep
• Time to Harvest: Typically 9-11 weeks when planted from seed.
• Mature Height/Spread: 0.5 to 1.5 meters (1.5 to 5 feet) tall.
• Grown From: Seeds

In most cases it’s best to start chilli seeds indoors 8–10 weeks before the last spring frost. The optimum soil temperature for germination is 21–29°C (70–85°F), which is a bit cooler than that stated in the general instructions in the next section below on starting seeds indoors.

Seedlings will emerge in around 8–25 days, and after the seedlings have developed two sets of true leaves they can be transplanted into larger pots around 7-10cm (3-4 in) wide. Seedlings should receive ample light indoors not be allowed to dry out.

If the chilli plants begin to flower while still indoors, pinch off the clusters of flower buds until the plants are ready to plant out in the garden, as the redirection of energy to the development of flowers and fruit will reduce their vegetative (leaf, stem and branch) growth.

How to Start Seeds Indoors: A Quick Step-by-Step Guide

To ensure a successful start to the gardening season, follow these steps to start seeds indoors. This early preparation helps plants get a strong start, ensuring they are well-prepared for transplanting outdoors and giving them the best possible chance for a productive growing season.

1. Prepare Containers and Soil: Use seed trays, pots, or any small container with drainage holes. Fill them with a sterile, well-draining seed-starting mix or fine potting mix (sift the big pieces out of potting mix with a small garden sieve).
2. Sow the Seeds: Plant seeds about 0.5 cm (1/4 inch) deep in the soil. Cover them lightly with the mix and very gently press down.
3. Watering: Water the soil gently to keep it evenly moist but not waterlogged. A spray bottle or small watering can with a fine watering rose works well for this.
4. Cover the Tray: Cover the seed tray with plastic wrap, a clear plastic lid, or a humidity dome to retain moisture and create a warm, humid environment to help speed up germination.
5. Provide Warmth: To encourage germination (sprouting), place the covered containers on a heating mat to keep the flat at 24-29°C (75-85°F), or on the warm top of an appliance such as a fridge, until seedlings emerge. Carefully monitor the moisture of the growing medium, as heating mats will dry the mix out faster. After the seedlings emerge, a soil temperature of 21°C (70°F) is best. Warm soil is better than cool.
6. Light: Once the seeds germinate (usually within 7-14 days), remove the cover and move the seedlings to a location where they receive 12-16 hours of light daily. If natural light is insufficient, use fluorescent or LED grow lights placed about 5-10 cm (2-4 inches) above the plants.
7. Maintain Moisture and Temperature: Keep the soil moist and maintain a warm environment (around 21°C or 70°F) until the seedlings are ready to be transplanted.
8. Thinning: Once the seedlings have two sets of true leaves (leaves resembling those of the parent plant, and not the differently shaped pair of dicot leaves that first emerge), they can be transplanted into pots of their own. If growing the seedlings in pots, thin them out by removing the weaker plants, leaving one strong seedling per pot.
9. Hardening Off: Before transplanting outdoors, gradually acclimate the seedlings to outdoor conditions over a week or two by exposing them to increasing amounts of sunlight and cooler temperatures.

Care and Maintenance

• Watering Tips: Keep soil consistently moist but not waterlogged. Water at the base of the plant to avoid wetting the foliage when watering in the evening. When leaves remain wet for too long and don’t have time to dry, this creates conditions favourable for fungal diseases to develop.
• Fertilization: Feed with a balanced fertilizer every 4 weeks or use a slow-release fertilizer at planting time.
• Support: Larger varieties may require staking or the use of cages to support the weight of the fruit and prevent branches from breaking.

Growing Difficulty

• Moderate, depending on the variety.

Growing Tips

• Avoid growing chillies in the same location each year, or in areas where other crops from the Solanaceae family such tomatoes, potatoes, and eggplant have been grown, to reduce disease buildup in the soil., through the practice of crop rotation.
• Mulching can help retain soil moisture, control weeds, and reduce soil temperature in very hot weather.
• To grow hotter chiles, water them only once a week and let the soil dry out between waterings. This stresses the plants which results in hotter pods.

Companion Plants

• Good companion plants include: Tomatoes, dwarf beans, basil, onions, and carrots.
• Avoid planting near: Climbing beans, fennel and kohlrabi.

Common Pests and Diseases

• Pests: Aphids, spider mites, and whiteflies.
  • Prevention and Control Methods: Use insecticidal soaps or neem oil. Encourage beneficial insects such as ladybugs.
• Diseases: Powdery mildew and bacterial spot.
  • Prevention and Control Methods: Ensure good air circulation around plants and use organic fungicide treatments if necessary.

Harvesting

Harvest Time:

• Harvest chillies when they have reached mature size. They can generally be generally picked green, or as soon as they change colour.
• Fruits should be smooth-skinned, and feel firm, plump, and crisp when squeezed, for best flavour and quality. It takes around 35-45 days from flowering to fruit maturing and reaching a full colour (red, yellow, orange) depending on the temperature and variety.
• Allowing chillies to change color increases their flavour and vitamin A content, and nearly doubles the vitamin C content.
• It’s also important to note that chillies don’t ripen further after harvesting.

Harvesting Tips:

• Use scissors or pruning shears to cut the fruit, rather than pulling, to avoid breaking the branches and damaging to the plant. Most pods can usually be taken from the plant easily if pods are mature.
• Harvest regularly as this will encourage the plants to continue flowering and set more fruit.
• At the end of the growing season, harvest all fruits that are mature and are green or slightly colored, as they won’t grow any further once the cooler weather sets in. 
• A common practice to pull entire chilli plants from the ground before a killing frost and hang them upside down in a warmer, dry area like a garage to allow unripe peppers to continue ripening. This method helps the peppers mature off the plant, especially when outdoor temperatures are no longer conducive to growth. The roots are often left intact, which supports the ripening process over the course of a few weeks

Storage:

• For optimal storage, harvested chillies should be kept in the refrigerator at a temperature of 7-10°C (45-50°F) with 80-90% humidity, allowing them to last for two to three weeks.
• Note that chillies are cold-sensitive and their skins may become pitted if they are refrigerated for too long.
• Some thinner-fleshed chillies, such as cayenne or Thai varieties, can be allowed to dry on the plant or harvested when fully ripe and hung up by their stems to dry. A common method for drying these chillies is by tying them together in long strings called ristras, a technique particularly effective in warm, dry environments where the risk of mold is low. Their thin walls allow moisture to evaporate quickly and evenly, making them ideal for air-drying.
• In contrast, thicker-fleshed chillies, like habaneros or rocoto chillies, are not well-suited for air-drying due to their higher moisture content, which increases the likelihood of mold developing before they dry fully. For these varieties, a dehydrator is a more reliable method to ensure thorough and even drying, while preserving their flavour and heat.

Propagation

• Propagate by seed. Seeds can be saved from ripe chillies, but be aware that chillies can cross-pollination when growing multiple varieties, and the seeds won’t grow to be the same as the parent plants.

Culinary Uses

Chillies are incredibly versatile in cooking and can be used fresh, dried, or powdered to enhance both heat and flavour in a wide variety of dishes. They are a staple in many global cuisines, prized for their ability to add complexity, spiciness, and even sweetness, depending on the variety and ripeness.

• Fresh chillies: Hot peppers can be eaten fresh, often chopped or sliced, and used in salsas, salads, and garnishes. They are also incorporated into stir-fries, soups, and sauces, where their heat intensifies during cooking. Green chillies are typically more tangy and sharp, while fully ripened red, yellow, or orange varieties provide a deeper, sometimes fruitier flavour.
• Cooked chillies: Fresh chillies can be roasted, grilled, or sautéed to bring out their sweetness and mellow the heat. Roasting, in particular, enhances the peppers’ natural sugars, adding a smoky richness to dishes like roasted chilli salsa or stuffed peppers. Cooked chillies are commonly used in sauces, stews, and curries, where their heat is gradually infused into the dish.
• Dried chillies: Many varieties of chillies are dried for long-term use. Dried chillies can be rehydrated in warm water and added to dishes for a concentrated burst of flavour, or ground into powder for seasoning. Dried chillies, such as ancho or guajillo, are common ingredients in mole sauces, marinades, and spice rubs.
• Chilli powder and flakes: Ground chilli powder, which can be made from a variety of dried chillies, is a pantry staple in many kitchens. It adds heat to rubs, spice blends, and seasoning mixes. Crushed chilli flakes, often made from cayenne or other hot varieties, are commonly sprinkled over pizzas, pastas, and grilled dishes for an extra kick.

Chillies are not only valued for their heat but also for the unique flavours they bring. Some varieties, like the habanero, add a fruity, tropical note to dishes, while others, like the smoky chipotle, introduce deep, earthy tones. Additionally, chilli peppers are commonly used to make hot sauces, chutneys, pickles, and infused oils.

In conclusion, growing chillies can be a highly rewarding experience for both novice and experienced gardeners. With a range of varieties available, gardeners can enjoy a range of flavours, colours, and heat levels. Proper care and attention will yield a prolific crop of peppers that can enhance a variety of culinary dishes.

References

• Growing peppers in home gardens. (n.d.-b). https://extension.umn.edu/vegetables/growing-peppers
• University of California Agriculture and Natural Resources, Master Gardeners of Santa Clara County. “Growing Peppers & Chiles.” UCANR. https://mgsantaclara.ucanr.edu/garden-help/vegetables/peppers/growing-peppers-chiles/.
• Chilli Pepper | Diseases and Pests, Description, Uses, Propagation. (n.d.). https://plantvillage.psu.edu/topics/chilli-pepper/infos
• Utah State University. (2024, February 1). How to grow peppers in your garden. USU. https://extension.usu.edu/yardandgarden/research/peppers-in-the-garden
• Dillion, D. (n.d.). Basics for growing peppers. N.C. Cooperative Extension. https://union.ces.ncsu.edu/2020/04/basics-for-growing-peppers/
• Growing chile peppers in New Mexico gardens | New Mexico State University – BE BOLD. shape the future. (n.d.). https://pubs.nmsu.edu/_h/H240/index.html
• Growing peppers in a home garden. (n.d.). University of Maryland Extension. https://extension.umd.edu/resource/growing-peppers-home-garden/