Pepper

Start pepper seed indoors 8 to 10 weeks before your last frost

Count back 8 to 10 weeks from your average last frost date and sow indoors. Hold the flat at 80F to 90F on a heat mat until the seedlings emerge, then grow them on at 65F to 75F with lights 2 to 3 inches above the tops for 14 to 16 hours a day. A transplant is ready when it is 5 to 8 inches tall and stocky with 6 to 9 mature leaves. Pepper seed germinates slowly and only in genuinely warm soil, and the plant needs a long warm season to set and ripen fruit, so a head start indoors is the difference between a crop and a few late fruits.

Set peppers out only once nights stay above 50F

Wait until soil has reached 60F and nighttime lows are reliably above 50F, which is usually well after your last frost date, not on it. Space plants 18 inches apart in rows 30 to 36 inches apart, setting them at the same depth they grew in the pot. Peppers stall in cold soil and abort their flowers when nights fall below 55F, so a plant set out early is often overtaken by one set out two weeks later.

Steady deep water from first bloom to prevent blossom-end rot

From the first flowers through fruit development, water deeply and infrequently to deliver 1 to 2 inches per week, keeping the soil evenly moist rather than swinging between soaked and bone dry. The soil should form a ball in your hand without breaking apart. Keep soil pH at or above 6.0. Blossom-end rot is a calcium shortage in the fast-expanding young fruit, and calcium rides to the fruit only in water moving through the roots, so a dry spell during early fruit set starves the fruit tip even when the soil holds plenty of calcium.

⚠ Foliar calcium sprays do not fix blossom-end rot, because calcium cannot move from leaves to fruit through the phloem. Correct the watering instead of spraying.

Black plastic to warm the soil, organic mulch only once it is hot

Lay black plastic mulch or black landscape fabric before planting to warm the soil, hold moisture and suppress weeds. If you prefer straw or herbicide-free grass clippings, wait until the soil is warmer than 75F, then lay it 3 to 4 inches deep. Organic mulch insulates soil rather than warming it, so laid down early it locks in the cold that peppers are trying to escape. Black plastic does the opposite and also stops rain from splashing soil-borne bacteria up onto the lowest leaves.

Side-dress nitrogen only after the first fruits have set

Wait until the first flush of peppers has set, then side-dress with nitrogen at about a quarter tablespoon per plant, placed 6 inches out to the side of the stem and watered into the soil. Utah State times the same two feedings at 4 and 8 weeks after transplanting, which is roughly when that first flush arrives. Apply phosphorus and potassium by soil test rather than by habit. Nitrogen given before fruit set buys leaves instead of peppers, producing a bushy, leafy plant that is slow to bear. Waiting until fruit is actually on the plant puts the nitrogen where it feeds the crop.

⚠ Keep the fertilizer 6 inches off the stem and water it in, as banded nitrogen against the stem burns roots.

Check the fruit stem cap for corn borer frass

As fruit sizes up through mid and late summer, look under the stem cap of developing peppers for brown, sawdust-like excrement at the edge of the calyx, which marks a borer entry hole. Hand-pick where numbers are low, or spray Bt when small larvae are first active and still feeding on leaves, before they tunnel in. The second corn borer generation is the damaging one because it arrives when fruit is on the plant. Larvae enter beneath the stem cap and feed on the seed core, and the entry wound lets soft rot bacteria in, so once a larva is inside the fruit no spray can reach it.

⚠ Bt is specific to caterpillars and spares bees, and pepper may be harvested four hours after application. Peppers flower continuously all summer, so do not reach for a broad-spectrum insecticide here, since there is no window when the plant is out of bloom.

Bacterial leaf spot: fixed copper on a 10 to 14 day interval

If small water-soaked spots with gray to tan centers and dark borders appear on the leaves and older foliage starts yellowing and dropping, spray fixed copper every 10 to 14 days to slow the spread. Start from clean seed and transplants, and rotate peppers to new ground if infection was severe last year. The bacterium spreads in splashing rain and on your own hands and tools, and it overwinters in crop residue and soil, so copper is a barrier that protects healthy tissue rather than a cure for spotted leaves. Losing the canopy also exposes fruit to sunscald.

⚠ Copper only slows spread and cannot cure infected leaves. Never work among wet pepper plants, as handling wet foliage moves the bacteria plant to plant faster than any spray can hold it back.

Cut peppers from the plant, never pull them

Cut the stem with snips or a knife rather than pulling, which snaps branches. Pick at full size and firm, plump, smooth skin. You do not have to wait for red. Full colour takes roughly 35 to 45 days from flowering, and leaving fruit to colour up costs further fruit set. Pepper branches are brittle and a pulled fruit tears the branch that was going to carry the next flush. Fruit left to ripen fully signals the plant to slow new fruit set, so green picking keeps the plant producing while colour picking buys sweetness and more vitamin A and C.

⚠ When you take the ripest fruit off a crowded plant you can suddenly expose shaded fruit to full sun and cause sunscald, so avoid cutting away leaves as you pick and shade harvested fruit promptly.