Want to make sure your seedlings can survive the outdoors? Learn when and how to start hardening off pepper plants so that they get strong enough to move outside.

Hardening off (acclimating) your plants to the outdoors is a really important, and necessary, process. I found out the hard way that indoor seedlings can suffer if they go outside without any preparation.

The warm, safe environment that your chile plants know is very different from the outside world. And, you just spent all this time growing peppers from seeds indoors — we’re not about to lose them now!

This guide explains when and how to harden off pepper plants. This way, your plants build up their defenses and have a much easier transition into the garden.

Table Of Contents

Let’s begin!

What Does It Mean To Harden Off Seedlings?

Hardening Off Definition

Hardening off (acclimating) is the process of preparing indoor seedlings to live outside. It means slowly exposing plants to the sun, wind, fluctuating temperatures and the other outdoor elements that they’ll face.

Essentially, acclimating pepper plants gives them the opportunity to build their natural armor as if they started life outside. Seedlings grow stronger stems and develop a waxy layer (cuticle) that shields leaves against things like dehydration and harsh sun rays when they are hardened off.

What Happens If You Don’t Harden Off Pepper Plants?

There’s a reason for hardening off seedlings before transplanting. Namely, transplant shock.

Young pepper plants need the opportunity to develop their natural defenses that avoid this shock. Otherwise, branches can snap in strong winds, leaves may burn in the heat and plants are more susceptible to insects and disease.

Even more, fluctuating outdoor temperatures can stunt pepper plant growth. Plants can even die if it gets cold enough.

So, how important is hardening off seedlings? Unlike the optional practice of pinching pepper plant flowers, hardening off seedlings is necessary. Taking two weeks to prepare your plants is nothing compared to the amount of time lost due to transplant shock or losing them altogether.

When To Start Hardening Pepper Seedlings

You can harden off pepper seedlings about two weeks before you transplant them outside. This means there won’t be any danger of frost and night temperatures are regularly higher than 55 degrees Fahrenheit (13 degrees Celsius) when they go outdoors.

The question of when to move pepper plants outdoors also depends on the growth stage. In general, pepper seedlings are about 8 weeks old, around 4 inches tall and they have a few sets of true leaves.

grow tips

Always check local weather reports so that you don’t start hardening off seedlings too early. Unexpected freezes and storms can happen!

How To Harden Off Pepper Plants

Hardening off pepper plants can take up to two weeks. The steps below are general guidelines to get you started with hardening off seedlings indoors and outside.

Hardening Off Seedlings Indoors

The first step is to run a small fan near your plants for 15 minutes on day one. Make sure the breeze is moving your seedlings around, but not so strong that your plants are whipping back and forth like crazy.

On the second day and for the rest of the week, increase the fan by 15 more minutes each day. For example, day two is 30 minutes, day three is 45 minutes and so on.

After the indoor process is complete, start the process for hardening off your pepper plants outside (see below).

Hardening Off Pepper Plants Outside

Start by putting your pepper plants in a shady spot outside. Leave them outdoors for 15 minutes, and then bring them back inside. (And, if the weather gets bad, bring your seedlings back inside immediately!)

hardening off seedlings outside in shade — Seedlings Hardening Off In Shade

Continue to bring your plants outside for an extended period of time each day. Like the indoor process, add 15 minutes more each day. Start giving your pepper plants more sunshine each day as well.

Around day six, check the weather for problematic conditions like rainstorms or low nighttime temperatures. (The temperature for hardening off seedlings shouldn’t dip below 55°F [13°C] at night.) If all looks good, leave your peppers out for a full day and night.

Your pepper plants are fully hardened once they’ve been outside for about a week.

After both hardening off processes are complete, you can transfer pepper plants to their new garden location. (If possible, choose a cloudy day to make this transition easier.)

grow tips

If you live in a gardening zone with a short growing season, start hardening off pepper seedlings as soon as possible. This means leaving plants outside for longer periods at a time (e.g., 30-minute + increments) to shorten the time frame. You can also experiment with putting plants outside when it’s cooler 46°F (8°C). As always, watch those young plants carefully when they’re outside.
Be sure to keep up with your water and fertilizer schedule during the hardening off process.

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After Moving Pepper Plants Outdoors

Even though we do our best to move pepper plants outdoors at the right time, unexpected climate changes can happen. The tips below provide solutions for common outdoor scenarios.

Temperatures are 90°F (32°C) or higher. This heat can cause sunscald and slower growth in pepper plants. Move your plants to a shadier area, or use a shade cloth (30% to 40%) to provide relief from the hot sun.
Night time temperatures are expected to go below 55°F (13°C). Move these tender plants back indoors for the night. If you have too many plants to bring inside, you can cover them with a frost blanket or bed sheet, and then remove it in the morning.

(Pepper plants won’t survive a freeze, but they should be able to live through temporary drops in temperature.)

Additionally, watch your chile plants carefully for signs of pests and disease. Good airflow, mulch and at least 8 hours of sun are just some of the ways you can avoid common problems.

hot fish pepper plant — Hot Fish Pepper Plant

FAQs About Hardening Off Peppers

Should I pinch buds off pepper plants when I harden my plants?

It’s not uncommon to see a flower or two growing on your seedling. You can pinch flowers and buds back to help your plant direct its energy reserves towards building a stronger root system while it gets used to being outdoors.

Do you need to harden off plants from a greenhouse?

Like other indoor environments, greenhouse plants need to be hardened off so that they have an easier transition when moving outside.

Do you need to harden off pepper seedlings that you buy?

If you buy from a local nursery and your plants are already outside, they are likely already hardened off. When pepper seedlings are indoors (or you purchase them online), harden off these plants to be safe. In all scenarios, give your plants a day or two in the shade before putting them in full sun to ease them into the new location.

How long do you have to harden off plants?

It usually takes one to two weeks to harden off plants, depending on the weather. Don’t harden off chilli plants during strong winds, storms or low-temperature days to keep them safe. And, always keep an eye on your plants during this process.

Do you have to harden off overwintered pepper plants?

Yes, repeat the hardening off process to help reintroduce your plants to the sun, wind and fluctuating temperatures outside. Winterized chile plants are more mature and are usually fully hardened in about a week.

What’s Next?

I hope this guide answers all of your questions about hardening off pepper plants. Your next step is to officially move your plants to outdoor pots. Check out the transplanting pepper plants guide for how to do this planting.

P.S. Even though this post is written for chillies, you can also use these steps for hardening off tomato plants and other seedlings too.

How to Harden off Pepper Plants Indoors and Outside

Active Time: 14 days

Total Time: 14 days

Difficulty: Easy

Chile plants need to be toughened up (hardened off) before they continue growing outside. Here's a 2-week process for how to harden off pepper plants.

Tools

Small Fan