The Serrano Pepper Planting Guide

Serranos are a quick, easy-going pepper to grow. They’re ready to pick about 75 to 78 days after they go in the ground, and it’s up to you whether you take them green or wait for red. They come from the mountains of Puebla and Hidalgo in Mexico, but they’ll ripen almost anywhere in the U.S. as long as you time the planting right. The planner below works your dates out from your zip code.

Want to know how hot they get and how they stack up against a jalapeño? That’s in our serrano profile. This page is all about growing them.

Sow Right Seeds Serrano Pepper Seeds

Non-GMO heirloom serrano seed, about 100 seeds to a packet, with growing instructions on the back. The peppers start green and ripen to a bright red, which is when they’re hottest.

Last update on 2026-10-20. We earn a commission if you make a purchase, at no additional cost to you.

Growing at a glance

Serrano Pepper

Heat: 10,000–23,000 SHU
Start seeds indoors: 8–12 weeks before your last spring frost
Germination: 7–21 daysIn soil around 70–85°F.
Harden off: 7–14 days before transplanting
Transplant: After last frost, once nights stay at 50°F or warmer
First harvest: 75–78 days after transplanting
Plant height: 24–36 inches
Containers: Does well in a container

Get these dates for your zip code

Where these figures come from

When to plant serranos where you live

Serranos can’t take frost, and they don’t do much in cold soil either. You’ll want to plant them out after your last frost, once nights stay at 50°F or warmer and the soil’s reached about 60°F.

Type in your zip code and you’ll get dates for starting seeds, hardening off, transplanting and your first harvest, all from NOAA frost data for your area, plus a check on whether your season’s long enough. For serranos it nearly always is: they ripen before frost in 98% of U.S. counties.

Map of U.S. counties showing where serrano peppers ripen before the first fall frost. Nearly every county fits; the ones that miss are scattered high-elevation counties in the West and a strip of northern Alaska.

Starting serrano seeds indoors

You’ll start the seeds 8 to 12 weeks before your last spring frost. Serrano seed can take anywhere from 7 to 21 days to come up, and it’s faster in warm soil, so keep the seed-starting mix between 70 and 85°F. When they’ve come up, give them bright light from overhead. Got a packet that’s been in a drawer for a few years? Check how long pepper seeds last before you count on it.

A week or two before transplanting, it’s time to start hardening them off. Set the seedlings outside a little longer each day so they’re used to being outdoors by the time they go in the ground.

Planting serranos outside

Sun matters most. Give them your sunniest spot: the University of Georgia recommends 8 to 10 hours of sun a day for peppers.

They’ll need about 18 inches between plants, in rows 30 to 36 inches apart. There’s more on spacing in how much space pepper plants need.

You’ll want well-drained soil with a pH of about 6.0 to 7.0. You’ll know where yours stands after a soil test, and our guide to the best soil pH for peppers covers what to do about it.

Once the plants are in, mulch around them with compost, straw or wood chips to keep the weeds down and hold moisture in. Just keep it off the stems. And if you lay black plastic down before planting, it’ll warm the soil, too.

Growing serranos in containers

Serranos do well in pots. Use a container of at least 5 gallons with drainage holes. Pots don’t hold water long, so once the plants are big and setting fruit, expect to water every day. There’s more in our guide to growing hot peppers in containers.

Watering and feeding serranos

They’ll want about an inch of water a week. If the rain doesn’t give them that, soak the soil thoroughly. Frequent light watering leads to weak roots, and uneven watering is tied to blossom-end rot. The planner above shows how much rain your area normally gets each month. Our post on watering pepper plants has the details, and here are the signs of overwatering pepper plants.

Go easy on the nitrogen, since too much of it gives you a lot of leaves and fewer peppers. Test your soil before you fertilize, and unless the test says you need phosphorus, use a low- or no-phosphorus fertilizer. Our guide to fertilizing pepper plants walks through what to use and when.

When to pick serranos

You can pick serranos green or red. The first green ones are ready about 75 to 78 days after transplanting, once they’re full size and firm. Green ones taste fresher and crisper, and they’re milder. Leave them on the plant and they’ll ripen to red and get hotter, but that’ll take longer.

Don’t pull them off. Use shears or pruners, since pepper branches are brittle and they’ll snap. If you’re picking a lot, wear gloves and keep your hands away from your face until you’ve washed up.

If frost is coming and you’ve still got green ones on the plant, pick everything. You can ripen peppers off the vine.

Common serrano plant problems

Few new peppers in a heat wave: very little pepper fruit sets once highs reach 90°F. The planner shows when that usually happens where you live.
Blossom-end rot: a brown rot on the bottom of the fruit, tied to calcium and uneven watering. See calcium deficiency in pepper plants.
Sunscald: see sunscald on peppers.
Curling or yellow leaves: see pepper plant leaves curling and pepper plants turning yellow.
Aphids and spider mites: see aphids on pepper plants and spider mites on pepper plants.
Plants that won’t grow: start with pepper plants growing slowly.
A frost on the way: see will frost kill pepper plants?

For the rest, we’ve got a rundown of common pepper plant diseases and problems.

Free printable

Get the free PepperScale Scoville Heat Chart

A printable, at-a-glance ranking of 25 chilies from sweet to scorching — with the jalapeño and Carolina Reaper as your reference points. Join the newsletter and we’ll send it straight to your inbox.

No spam — just Wicked Wednesday recipes and occasional extra dashes of chili pepper inspiration. Unsubscribe anytime.