Introduction
Writing a guide to growing sweet peppers can be daunting due to the variations among different varieties, sowing dates, weather conditions, and the availability of grow lights. For example, in 2021, while some growers in the south struggled to harvest even a single pepper by September, others were picking theirs as early as July with similar methods. However, over the years, a systematic approach has been developed to minimize these variables, resulting in consistent and excellent outcomes.
- Sow: December - March
- Time to Maturity: 6-9 months
- Module Sow: 1 seedling
- Spacing: 12 inches apart, or 5-6 plants per m²
- Frost Tolerance: No, maintain temperatures above 11°C for best results
- Watering: 1 inch every 2 weeks during dry spells
- Planting: In full sun or light shade
Why Grow Sweet Peppers
A rating system can help determine what to grow, considering factors such as taste, health benefits, cost, harvest size, timing, and organic availability. Sweet peppers generally score moderately well, being exceptionally tasty, relatively expensive to buy, and capable of providing a decent harvest. Starting them early and maintaining temperatures above 11°C throughout their life can significantly increase yield. Their long harvest period and versatility make them a great choice; the fruits hold well on the plant and can be used at various stages of ripeness.
However, sweet peppers require dedicated care, and achieving a good yield demands time, effort, and sometimes financial investment.
How Many to Grow?
Yield can differ significantly among varieties, with plants grown in pots typically producing less than those planted in the ground. A good rule of thumb is that six plants should suffice for one person, leading to a recommended planting density of six plants per m².
Suitability for Different Growing Environments
Peppers are particular about their growing conditions. They thrive in warm, sunny environments but can benefit from some shade during the height of summer. They are vulnerable to early frost, and impatience can lead to losing up to 20% of plants in the worst years. While chilis grow well in containers, sweet peppers are often better suited for ground planting, as this reduces the need for constant watering. They prefer slightly acidic soil but can adapt to slightly alkaline conditions as well.
Lifecycle
Peppers grow slowly, particularly when they lack sufficient light or heat. Striking the right balance is crucial, with a preference for abundant light as long as temperatures remain above 11°C. Starting seeds early is essential, but timing depends on maintaining adequate temperature and light. From sowing to planting, the process can take three to four months, which is the longest duration for any crop. Peppers typically flower in late spring and summer, with fruits ripening through summer and autumn.
Although they can continue to bear fruit longer under optimal conditions, doing so is often not cost-effective. Thus, it's not a practice typically undertaken. Sweet peppers are self-fertile, meaning fruit can set without the need for pollinating insects or manual fertilization.
These plants are perennial, and it is possible to save them from one year to the next by pruning and storing them above freezing. However, this method requires significant space—approximately six times that of growing new plants—so it's usually not practical.
Sowing and Harvesting Periods
A lengthy harvest period is desirable since many peppers are consumed fresh, and a synchronized harvest with tomatoes is essential for making sauces and ketchups. Frozen peppers can be harvested at any time, so timing is less critical for that portion.
First Earlies (Sow in Early December for Harvest in Early Summer)
Starting a quarter of the sweet peppers in December allows for an early harvest. Using grow lights, a dozen sweet peppers can be started, providing a manageable quantity for windowsill space. By early summer, fresh peppers will be welcomed after depleting frozen supplies.
Second Earlies (Sow in Early January for Harvest in Mid-Summer)
Historically, peppers were not started in January due to space constraints. However, it became evident that the harvest from January-sown peppers significantly outperformed those sown later. Thus, the planting quantity was adjusted accordingly, reducing the need for a larger space.
Early Main Crop (Sow in Early February for Harvest in Mid-Summer)
A small number of spare plants can be sown in mid-February as a backup, taking minimal space as they remain in trays until planting. This batch offers a follow-on harvest from the first earlies and will continue to produce through summer, slowing down in September.
Main Crop (Sow in Late February for Harvest in Late Summer)
While late February sowing is no longer practiced, it may still be advisable for those without grow lights. These plants typically require 30 days under grow lights, which aid their growth significantly.
Late Crop (Sow in Summer for Harvest in Winter)
Alternative strategies include continuing early sowings indoors for a very early crop, sowing plants in summer for indoor growth, or cutting back plants in autumn to overwinter them. However, this is generally avoided due to space constraints, inferior taste, low yield, and the risk of harboring pests. Nonetheless, with adequate warmth and light, plants can be visually appealing, and this can be enjoyable if no other crops are being grown. Hot peppers tend to be more worthwhile than sweet peppers, but freezing the summer crop is typically more beneficial.
How to Sow
Peppers should be germinated in a propagator or a warm indoor spot. A basic propagator can raise ambient temperatures by approximately 10°C, making it ideal for starting peppers indoors. It's essential to maintain a stable temperature; thus, the propagator should be placed away from radiators and direct sunlight.
Warm Up the Materials
It's advisable to bring compost and water indoors for a few hours before sowing. While this isn't strictly necessary, it can be helpful for achieving slightly warmer conditions. The compost should be slightly moist but not wet.
Sowing Process
Sowing is straightforward: lay the seeds flat on the compost surface, spacing them about 1 inch apart to prevent root tangling. Cover the seeds lightly with compost, approximately 5 mm (1/4 inch) deep. Lightly water from above without saturating the compost. Place the tray in the propagator with the lid on; keeping the vents open allows for natural watering through condensation.
Alternative Germination Method
This year, a successful method involved chitting peppers on kitchen roll, requiring no propagator or heat mat—just a Tupperware container on a windowsill near a radiator, maintaining a temperature of around 16-18°C.
Once seedlings emerge after 7-14 days, remove the lid and position them in a sunny spot or under grow lights. It's crucial to keep the seedlings above 11°C, ideally between 15-18°C, which aligns with standard room temperature. While not all seedlings will sprout simultaneously, once a few emerge, the rest typically follow within the week.
Keep the seedlings lightly top-watered, as they require minimal moisture at this stage.
How to Prick Out/Pot On
Seedlings started under grow lights can be pricked out at about three weeks old, once true leaves begin to appear. Although small, the seedlings should have developed a solid root system by this time. Delaying this process could lead to competition for space among the roots, but they should still thrive.
For seedlings started without grow lights, they may require more time to reach the right size.
Seedlings sown from December to early February will likely need potting on twice, while those sown in late February or March might only need one potting on.
Watering Considerations
Watering frequency can vary based on weather conditions; generally, every 2-3 days is sufficient, allowing the compost surface to dry between waterings.
First Potting On
For the initial potting, a 6-cell tray is recommended, especially as six plants fit neatly into a 1 m² bed. These trays can accommodate plants for around six weeks. Use seed compost for early sowings to promote slower growth, and switch to potting compost for the second potting or later sowings.
This year, feeding with Chili Focus has significantly improved plant health.
Plants remain in their pots until May, sometimes late May, depending on weather conditions. They receive 60-90 days of light (based on the sowing date) before transitioning to natural light in a conservatory.
Compost Management
Compost tends to shrink over six weeks; refilling after about four weeks adds nutrients and improves water retention. Burying the stems is not a concern.
Managing Flowers
Plants will begin to flower after about two months. Leaving a few flowers on taller plants allows for early detection of pests, while removing most flowers encourages a more substantial yield. Some growers recommend removing all flowers before planting, so experimentation is encouraged.
Where to Plant
Peppers should be kept well above freezing, as they are more vulnerable to late frosts than tomatoes. Maintaining a temperature above 11°C with ample light ensures fast, healthy growth and excellent yields.
Planting Conditions
- Ideally, plant under cover from mid to late May, when nighttime temperatures forecasted to be above 10-11°C. Outside planting is generally safe by early to mid-June.
- If planting earlier, fleece may not suffice; additional heating may be required. While fleece can keep plants alive, overall yields will likely be lower than if sown and planted later.
- Ensure a warm, sheltered, and sunny location for outdoor planting, ideally against a south-facing wall for optimal heat absorption.
- Consider wrapping plants in fleece or bubble wrap during the first couple of weeks after planting.
- Preferring to grow peppers in the ground or 30-litre pots allows them to become large plants.
- Low tunnels often yield better results than greenhouses or polytunnels, as they prevent excessive heat buildup in summer. They can be closed during warm springs and opened gradually as temperatures rise.
- Low tunnels are particularly effective for autumn, winter, and spring crops but are less productive in summer except for peppers.
How Many to Plant (Spacing)
Six plants per bed in a little over 1 m² is ideal, resulting in about 5-6 plants per m², depending on the variety. While they may appear sparse at planting, by mid-summer, they will fill the space completely. For containers, opt for 30-35 litre pots.
How to Plant
Preparing the Soil
Warm the soil before planting by closing low tunnels for a week ahead of time. While waiting, the soil may remain populated with spring crops.
The planting process includes:
- One week before planting, remove the tops of the previous crop (e.g., lettuce, spinach).
- Apply amendments, generally using a slow-release organic fertiliser with seaweed (liquid feed is used after fruit set).
- Water the ground well, particularly if it's been lightly watered throughout winter and spring.
- Apply a 1-inch surface mulch of weed-free compost, leaving the low tunnel lid closed to warm the soil and retain moisture for a week.
- A day or two before planting, vent the tunnel slightly.
- On planting day, create a hole using a bulb planter to minimise soil disruption.
- Shape the hole with a plant pot to match the pepper plant's pot size.
- Pre-water the hole with warm water mixed with a little liquid seaweed fertiliser.
- Place the pepper plant into the hole without disturbing the roots.
- Lightly water in with warm water.
- Insert a support cane and secure the plant.
- Close the low tunnel or leave it slightly vented, depending on weather conditions.
- Monitor and adjust ventilation for the first few weeks based on the weather.
Additional Protection
If cold weather threatens, consider using a candle under a terracotta plant pot with a roof tile on top to maintain warmth.
Protecting and Supporting Your Plants
Growing 48 plants under polythene low tunnels, alongside another 12 outside, has proven effective. The plants are supported by a sturdy cane inserted during planting. The low tunnel tops offer additional support as the large plants' leaves and branches touch the plastic.
Optimal Temperature Ranges
Plants thrive best in a nighttime temperature range of 15°C to 20°C and a daytime range of 19°C to 28°C. While these temperature ranges are ideal, it's crucial not to obsess over them, as plants typically adapt well to normal conditions.
How to Feed and Water
For plants in the ground, watering occurs once a week, coinciding with the application of a liquid feed. The same feed is used for both tomatoes and peppers, with a 5-litre container lasting all year.
During extremely hot weather, it may be necessary to water six plants twice a week with a 10-litre watering can. Conversely, earlier and later in the season, once a week is usually adequate.
For container plants, particularly during the hottest summer days, watering may be required up to twice daily for 20-litre pots; larger 30-35 litre pots should generally need watering once a day. Avoid overwatering—soil should remain moist, not saturated.
How to Prune/Manage While Growing
Pruning is not typically performed. Attempts to remove growing tips for bushier plants have shown no significant benefits. The plants naturally bush out once their stems are sturdy enough to support additional branches.
In rare cases, plants may outgrow their low tunnels and require pruning; however, this is uncommon. By mid-summer, low tunnels can no longer be closed, but the plants will expand to fill the available space, providing adequate support against summer and autumn storms.
How and When to Harvest
Harvesting options for peppers include:
- Fully Green: Some prefer green peppers; about 20% may be harvested early in the season. Picking one green pepper per plant seems to stimulate growth, leading to a more substantial overall crop.
- Beginning to Change Colour: Any color other than green indicates ripening. A patch of color often signifies that the pepper will be ripe within a week. Harvesting at this stage, especially in autumn or when cooking, encourages larger yields, with about 50% of the harvest taken at this point.
- Fully Coloured: These peppers are ready to eat and make up around 30% of the harvest, ideal for fresh consumption.
Harvesting can occur continuously from late June until mid-October, with some peppers ripening off the plant until November using very ripe windfall apples, which are more effective than bananas.
Ripening Note
Peppers that are entirely green rarely ripen off the plant; however, any signs of colour development ensure consistent ripening.
How to Store
Most peppers are consumed fresh or cooked within the week following harvest, while excess is frozen for later use.
How to Deal with Pests and Disease
Pest and disease management is limited; the primary pest concern is greenfly, along with occasional blossom end rot.
