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.
- What Does It Mean To Harden Off Seedlings?
- What Happens If You Don’t Harden Off Pepper Plants?
- When To Start Hardening Pepper Seedlings
- How To Harden Off Pepper Plants
- After Moving Pepper Plants Outdoors
- FAQs About Hardening Off Peppers
- What’s Next?
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.
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!)
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.)
- 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.
FAQs About Hardening Off Peppers
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
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.
- Small Fan
Hardening Off Seedlings Indoors
- Run a small fan near your plants for 15 minutes on day one. (When hardening off seedlings with a fan, make sure the airflow isn't so strong that it's whipping your plants around like crazy.)
- Continue using the fan every day while your plants are indoors. Increase the duration by 15 minutes each day. For example, on the 2nd day run your fan for 30 minutes, the 3rd day for 45 minutes and so on.
- Keep running your fan every day for up to a week. When done, start the process for hardening off your seedlings outside.
Hardening Off Pepper Plants Outside
- Put your plants outside in a shady spot for 15 minutes on day one. Afterwards, bring them back inside.
- Continue putting your plants outside and increase this outdoor time by 15 minutes each day (e.g., 30 minutes on day two, 45 minutes on day three, etc.). Give your plants more direct sunlight each day as well.
- Check the weather around day 6, and then leave your plants out for a full day and night. The temperature for hardening off seedlings shouldn't dip below 55°F (13°C) at night.
- Continue hardening off your pepper plants outside for about a week.
- If your plants are outside in bad weather, such as high winds or heavy rain, bring them back inside right away.
- If your plants show signs of stress while outdoors, put them in a shadier spot to help them recover.
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