Forest Girl Farm

A pepper plant covered in blossoms that keeps dropping every one of them isn’t a sick plant. Nine times out of ten near the coast, it’s a temperature problem — and the number that matters isn’t the afternoon high, it’s the low at 4 a.m.

What temperature makes peppers drop their flowers?

Pepper pollen goes sterile when nights dip below about 55°F or days climb past roughly 90°F. The flower still opens, the plant still spends the energy, but nothing gets fertilized and the blossom drops within a few days.

Here in the Santa Cruz Mountains, our July and August nights routinely sit in the low 50s under the fog, even when the afternoon feels warm. That’s the whole story for a lot of struggling pepper plants around here. It also explains why peppers on this side of the hill so often go crazy in September and October — our warmest, clearest stretch is the tail end of the year, not midsummer.

How do I get peppers to set fruit in a cool coastal garden?

• Trap heat at the roots. Dark mulch, a black nursery pot sunk beside the plant, or a stone or brick on the south side holds warmth into the night. Straw mulch is great for tomatoes and works against you here — it insulates the soil from the sun.
• Give them a wall. A south- or west-facing fence, wall, or even a row of grow bags on a warm patio can buy several degrees over an open bed.
• Cover them at night. Row cover draped over hoops from evening until mid-morning holds a few degrees and takes about two minutes a day.
• Ease off the nitrogen. Too much and you get a gorgeous three-foot bush with nothing on it. Once buds appear, switch to something lower in N and higher in phosphorus and potassium.
• Give the plant a shake. Peppers self-pollinate but need movement. A gentle flick of each flowering branch around midday, when it’s driest, genuinely improves set.

Which pepper varieties actually produce here?

Variety choice does more than any trick on that list. Skip the 90-day bells and look for anything bred short-season or cool-tolerant:

• Jimmy Nardello — sweet Italian frying pepper, reliable and heavy-bearing even in a cool summer
• Lipstick — thick-walled sweet pimiento type, ripens red in about 75 days
• Padrón — picked small and green, so it doesn’t need a long ripening window
• Ace — a bell bred to set fruit in cool conditions, which most bells simply won’t do
• Shishito — fast, forgiving, and keeps producing right through fall

If your plants are healthy and blooming, don’t pull them out in frustration this month. Warm the soil, hold off on the nitrogen, and let them ride into our real summer.

Are your peppers setting this year, or still all flowers and no fruit?