How to Grow Peppers: Start Early, Then Keep Them Warm

Peppers are grown alongside tomatoes and treated like tomatoes, and that is where most of the trouble starts. They need more heat, more time, and less feeding.

Start them when you start your tomatoes and you will be planting out undersized plants that never catch up.

Starting from seed

Timing: eight to ten weeks before your last frost date. Hot varieties want the longer end, because they take 90 to 150 days from transplant.

Heat: this is the part people miss. Pepper seed wants 80 to 90°F to germinate well. At room temperature it germinates erratically over three weeks or more, and half of it may not come up at all. A heat mat under the tray transforms the result — most seed up within a week.

Light is irrelevant until they emerge. Warmth is everything.

Once up, light becomes everything instead. Peppers stretch badly in weak light. A bright south window is marginal; a simple grow light a few inches above the seedlings is much better.

Planting out

Wait for warm nights. Nights reliably above 55 to 60°F, which is usually two to three weeks after your last frost. Peppers set into cold soil sit still and sulk, and a plant put out a fortnight later routinely overtakes one rushed out early.

Harden off over a week or ten days.

Spacing: 18 to 24 inches apart. Some growers plant peppers closer deliberately so the plants shade each other’s fruit and prevent sunscald — that works, at some cost in airflow.

Soil: well-drained, moderately fertile, pH 6.0 to 6.8, with compost worked in.

Water, feed, and the nitrogen trap

Water consistently — about an inch a week, deep rather than frequent, at the base. Mulch two to three inches to hold it steady. Erratic watering causes blossom end rot on peppers exactly as it does on tomatoes, and for the same calcium-transport reason.

Feed lightly. Balanced fertiliser until the first flowers set, then switch to high potassium every one to two weeks.

Too much nitrogen gives a magnificent dark-green plant with almost no fruit. Peppers are more sensitive to this than tomatoes, and it is the most common reason a healthy-looking plant produces nothing.

Flower drop

Peppers drop flowers readily, and it is nearly always temperature:

Hand-pollination is easy and often worth it under cover, where there is no wind and no insects: a gentle tap on the stem, or a small brush inside the flowers.

Support and sunscald

Pepper branches are brittle and snap under a load of fruit. Stake or cage plants that are carrying well — a single stake and soft ties is usually enough.

Sunscald — pale, papery, sunken patches on the fruit — happens when fruit is exposed to intense direct sun, often after leaves have been removed or lost to disease. Keep the canopy intact, and use shade cloth in extreme heat.

Harvest

Peppers are edible at any stage, but colour is where the flavour is.

• Green — the immature stage of most varieties. Firm, grassy, less sweet.
• Red, yellow, orange, purple, chocolate — fully ripe. Sweeter, higher in vitamin C, and in hot varieties, hotter.

Waiting for colour costs you time and total yield, because a ripening fruit slows the plant’s production of new ones. Picking green keeps a plant producing longer. Neither is wrong — decide which you want.

Cut, do not pull. Pepper stems snap easily and pulling takes the branch with it. Use snips and leave a short stub.

Picking regularly keeps the plant setting new fruit. As with cucumbers, a plant allowed to fully ripen everything it carries slows down.

Overwintering

Peppers are perennials grown as annuals. In a mild climate, or under cover, you can cut a plant back hard in autumn, keep it barely moist and above 55°F, and start it again in spring.

An overwintered plant fruits weeks earlier than a new seedling, which matters most for hot varieties with very long seasons.