How to grow peppers indoors

Choosing a container

Use a minimum 5-gallon container per plant; compact varieties (e.g., 'Lunchbox', 'Chenzo') can get by in 3 gallons, but larger containers buffer moisture and nutrient swings better.

Drainage is non-negotiable. Ensure at least one drainage hole and never leave the pot sitting in a saucer of standing water for more than an hour — root rot is the most common indoor pepper killer.

Light: the critical factor

Peppers are high-light plants. A south- or southwest-facing window is the minimum baseline; west-facing windows can work in summer. University of Minnesota Extension classifies peppers as needing more than 1,000 foot-candles (roughly 200–450 µmol m⁻² s⁻¹ PPFD) for healthy growth.

For reliable fruiting indoors, supplement with a full-spectrum LED grow light positioned 4–6 inches above the canopy for low-power LED or fluorescent fixtures, and farther for high-output panels. Run lights 14–16 hours per day for mature fruiting plants; seedlings need at least 13 hours. Without adequate overhead light, stems etiolate and lean, and fruit set drops sharply.

Temperature

Daytime temperatures of 70–80°F and nights of 60–68°F are ideal for vegetative growth and fruit set. Below 55°F causes chilling stress; above 90°F causes blossom drop.

Keep containers away from cold drafts near windows in winter and from heating vents that cause erratic soil drying.

Starting from seed indoors

Pepper seeds require warm soil — 80–90°F — to germinate reliably. Use a seedling heat mat under the tray until sprouts emerge, then remove it. Germination typically takes 14–28 days.

Sow seeds 8–10 weeks before you want transplant-size plants.

1. Fill small cells or 2-inch pots with a sterile seed-starting mix.
2. Plant seeds ¼ inch deep, two seeds per cell.
3. Keep the medium at 80–90°F using a heat mat; keep it evenly moist but not saturated.
4. Once seedlings emerge, move to full light immediately to prevent leggy growth.
5. Thin to one seedling per cell once the first true leaves appear.
6. Pot up to a 4-inch container when roots reach the cell walls, then to the final 5-gallon pot.

Watering and feeding

Water when the top inch of soil feels dry. Soak thoroughly until water drains from the bottom, then discard the drainage. Inconsistent watering is a cause of blossom-end rot, a calcium-uptake disorder triggered by moisture stress.

Container-grown peppers need more frequent fertilization than garden plants because nutrients leach with watering. Apply a balanced vegetable fertilizer (e.g., 10-10-10) at planting, then a dilute liquid fertilizer every 2 weeks once flowering begins. Avoid excess nitrogen after flowering — it pushes leafy growth at the expense of fruit.

Pollination indoors

Peppers are self-fertile — each flower carries both male and female parts — but they rely on vibration (normally from wind or bees) to release pollen effectively. Indoors, with no wind or pollinators, fruit set can be poor.

Once flowers open, gently shake the plant or run a soft electric toothbrush or small fan across the open flowers for a few seconds each day. Do this for the 2–3 days each flower is open.