How to Protect Your Pepper Plants From Cold and Frost


If you are like most gardeners, you want to get your pepper plants started as early as possible.  You also want to keep growing them for as long as possible.

However, the weather does not always cooperate, and late spring frosts or early fall frosts can kill your plants.

So, what is the lowest temperature pepper plants can tolerate?  A temperature of 32 degrees Fahrenheit or below will result in frost, which will kill your pepper plants.  Any temperature below 55 degrees will slow down the growth of mature pepper plants, and will stunt seedlings.  Peppers grown from seed should not be exposed to soil colder than 75 degrees Fahrenheit.

Luckily, there are plenty of ways to protect your pepper plants from cooler temperatures.  Taking a few of these measures at the beginning and end of the season can extend your season by a few weeks.  (You do want more peppers, don’t you?)  Let’s take a look at some of the ways to protect your peppers from cold – given in approximately chronological order.

Choose The Right Pepper Varieties

The first step is to choose the right pepper varieties for your climate, before you can even think about when to germinate seeds, transfer seedlings, or choose a location in your garden.

Based on where you live, the USDA plant hardiness zone map will tell you what zone you live in.

In general, the lower the zone number, the harder it will be to grow peppers for a long season.  If you live in a colder region, consider these two things.

Cold Tolerant Pepper Plants

If you do some research, you can find some cold-tolerant pepper varieties that will do well in your region.  One example is the Manzano pepper.

The Manzano pepper blooms in late summer and fruits into the fall.  It prefers temperatures from 45 to 60 degrees Fahrenheit, so you can even give them a cooler, shady spot in the garden!  However, frost is still deadly for these pepper plants.  For more information, check out the Manzano pepper on sandiaseed.com.

The Bulgarian Carrot Chile also tolerates colder temperatures.  You can also check out the Bulgarian Carrot Chile on sandiaseeds.com.

Fast Maturing Pepper Plants

Even if you have a short summer in your region, you can still get a good pepper harvest, provided that you grow them fast enough.  There are several fast-maturing pepper varieties to choose from.

One example is the Sweet Banana Pepper, which is not very spicy, but produces quickly.  You can check out the Sweet Banana Pepper on sandiaseeds.com.

banana peppers
Banana peppers mature very quickly.

Another fast-growing pepper is the Padron Sweet Spanish Heirloom Pepper.  You can check out the Padron pepper on sandiaseeds.com.

Planting Schedule

By now, you have decided on the varieties of pepper that you want to grow.  Now, take a look at the time to maturity (the seed websites should have this information, or you can find it on the seed packets).  For example, the Padron Pepper (mentioned above) has a time to maturity of 65 days.

 You also want to find the first chance of frost in your area.  The Farmer’s Almanac has a tool that you can use to find the dates for your region.

For example, the first chance of frost in my area is October 1st.  So, I will want to harvest my peppers by September 30.  Then, I work 65 days backwards from there: 30 days in September, 31 days in August, and 4 days at the end of July.

That means I would want to plant my pepper seeds by July 28 at the absolute latest.  Of course, my peppers would not do very well as the nighttime temperatures get into the 40s.  Planting earlier than this would be much better for my harvest.  Hopefully, this example illustrates the point about how to plan ahead for your garden.

Start Seeds Indoors

For most pepper seeds, the soil temperature needs to be 75 to 80 degrees Fahrenheit to achieve germination.  Your soil may not get that warm until late in the season.

You have two choices to bypass this limit: either buy established pepper plants from a garden center, or start your own pepper seeds indoors.

The question is, when should you plant the seeds?  It will depend on the variety of pepper plant you choose.

However, a good guideline is to plant the seeds 6 to 7 weeks before the last chance of frost, and transplant them 2 to 3 weeks after the last chance of frost.  This means that the plants will be indoors for 8 to 10 weeks total.

You can find the last frost dates using this map from the Farmer’s Almanac.

For example, let’s say the last frost is May 8, and I want to plant the pepper seeds indoors 6 weeks (6×7 = 42 days) before that date.  Working backwards, we find: 8 days in May, 30 days in April, and 4 at the end of March, for 42 days total.  So, I should plant the seeds indoors on March 27.

Keep in mind that the soil temperature should be kept at 75 to 80 degrees Fahrenheit for ideal germination of your pepper seeds.

Let’s say I decide to transplant the seedlings outside 3 weeks (3*7 = 21 days) after the last chance of frost.  Working forwards, we add 21 days to May 8, giving us May 29.

One more thing to remember: you can use artificial lights to grow your plants, or you can use sunlight from a window.  If you do place pepper seedlings close to a window, just be sure that they don’t get caught in a cold draft.  Otherwise, your season for growing peppers could be over before it really begins!

If you have trouble getting your pepper seeds to sprout, check out my article on how to get your pepper seeds to germinate.

Watch Weather Forecasts

Even if you are careful about choosing pepper varieties and timing your planting, nature may have other plans.  The dates for first and last chance of frost are usually reliable.  However, once in a while, you will see a year with strange weather patterns.

In this case, you should watch the short-range and long-range weather forecasts when it gets close to the time that you transplant seedlings outdoors.  If you see a forecast for a stretch of unseasonably cold weather or an extremely cold night, keep the pepper seedlings indoors for a little longer.

Apply Cold Treatment

You also have the option of applying cold treatment to your pepper plants, in order to toughen them up.  The idea is to expose them to weather a little colder than they would like (not freezing temperatures!), before they really get going.

Ideally, you would put the pepper plants in a location with plenty of light and a temperature in the low to mid 50’s (50 to 55 degrees Fahrenheit) for four weeks.  This cold treatment forces the pepper plants to put more energy into developing roots, stems, and branches.

In the short term, cold treatment slows down the growth of the pepper plant.  In the long term, cold treatment will give you more flowers and peppers.  It also makes the plant more resistant to cold.

If you have a short growing season, you might not have time for cold treatment.  Being more resistant to cold will not help your pepper plants in a frost.  However, if you have a longer growing season and want to increase yield, cold treatment is an experiment you can try.

Select the Best Locations

If you choose to grow some of the cold-tolerant pepper varieties mentioned earlier, you might be able to plant them in cooler, shady spots in your garden.

chili peppers
A chili pepper plant can produce red, green, or yellow fruit.

However, if you are planting standard varieties, choose a spot in your garden that gets more sun.  More sun exposure will make the soil warmer during the day, and that heat will last longer at night.

If there is an area of your garden that is shaded from wind, that can also help to keep your pepper plants a little warmer. If you want to find out ways to provide your own shelter, check out my article on how to protect plants from wind and storms.

Use a Cold Frame for Seedlings

Sometime, you want to transplant your seedlings outside a little earlier.  Other times, your spouse yells at you for having too many plants in the house.  Either way, a cold frame can help you out.

A cold frame is a short wooden structure with a glass top.  It acts as a mini greenhouse, and many of them open automatically when the temperature inside gets too high, and close again when it gets low.

You can transplant your seedlings directly into the cold frame when they are mature enough, and when the temperature gets high enough.  Just put a thermometer in the cold frame and monitor it every day.

You can also use a cold frame for cold treatment if you transplant earlier in the season.  Just make sure to watch out for frost in the weather forecast!

Use a Greenhouse for Taller Plants

If you want to protect your pepper plants from cold temperatures throughout the growing season, then transplanting directly into a greenhouse is a good option.  You can build one yourself, hire someone to build it for you, or possibly even purchase a pre-fabricated greenhouse.

As with a cold frame, you should put a thermometer inside your greenhouse and monitor the temperature.  If daytime temperatures are consistently 65 to 70 degrees Fahrenheit, and nighttime temperatures are consistently above 55 degrees Fahrenheit, then you can think about making the move from indoors to the greenhouse.

chili pepper plant
A chili pepper plant., displaying green peppers and red (more ripe) peppers.

If you move your pepper plants to the greenhouse early, make sure to keep the door closed to keep heat trapped inside.  Otherwise, you could damage or lose your pepper plants on a cold night!

Remember that pepper plants can also be adversely affected by high temperatures, and a greenhouse is capable of generating those temperatures on hot, sunny days.

Look at the weather forecast regularly.  If the forecast calls for a hot, sunny day, then leave the greenhouse door open before you leave for the day.

Use Cloches for Young Plants

An easier, low-cost alternative to a cold frame or greenhouse is a cloche.  A cloche is simply a cover meant to protect plants from cold temperatures.  Originally, a cloche was a bell-shaped glass cover to put over plants.

You can also use a plastic cloche to trap heat.  A wire cloche is often used to protect plants from rabbits or other creatures, but it won’t keep the plants warm.

The top of a cloche has a hole to allow plants to breathe, and to allow excess heat to escape.  Conveniently, a cloche can also deter some pests from damaging your pepper plants.

If you want to make your own cloche, simply collect empty plastic gallon containers of milk or water.  Then, cut out the bottom, and put the container over your plants.  Make sure to remove the cap on top of the gallon jug to allow the plants to breathe.

The only downside of a cloche is that your pepper plant will eventually outgrow it.  However, a cloche is a good way to keep young plants warm if you transplant early, or if an unseasonably cold spell comes through.

Use Row Covers for Taller Plants

What should you do if your pepper plants are too tall for cloches, but still need cold protection, perhaps towards the end of the season?  In this case, use row covers to keep your plants warm.

One way to do this is to fashion flexible plastic rods into half-hoops, with both ends stuck into the ground.  Once you have enough of these rods along the row, put a length of garden fabric over the hoops.

You can also use a tomato cage to hold up a row cover over a pepper plant to keep it warm. As an added benefit, it will provide support for the plant as it grows. For more information, check out my article on why to use tomato cages.

In addition to protecting from cold, your plants will be protected from pests.  As with a greenhouse, high temperatures can spell trouble for plants under a row cover.  If the temperature rises above 85 degrees Fahrenheit, then take the cover off, and replace it when temperatures cool down (such as at night).

Pinch Off Early Flowers

This technique is totally optional, just like cold treatment (mentioned earlier).  However, it is similar to cold treatment in that it can toughen up your pepper plants and increase your yield.

The idea is to pinch off some early flowers from your plants.  Instead of putting energy into developing fruit, the plant will take its energy and strengthen its roots, stems, and branches.

pepper flower
Pinching off flowers is not fun for any gardener, but it can make your plants stronger in the long run!

After the plant gets stronger, let it flower and grow its fruit.  The result will be more and larger fruit, and a plant that is more resistant to wind and cold.

Again, this is a method that slows down your harvest in the short term, but improves the harvest in the long term.  You may not have time for this in a colder climate, but together with cold treatment, it can really toughen up those pepper plants!

Conclusion

By now, you should have an idea of the temperature range that your pepper plants can tolerate before they slow down or die from cold.  You also have plenty of ideas on how to protect your pepper plants, extend the growing season, and increase your harvest.

I hope this article was helpful.  If you have any questions, or if any of these ideas worked well for you, please leave a comment below.

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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