Basil’s Temperature Tolerance

Temperature is a crucial factor in keeping your basil healthy and happy. We'll talk here about basil's temperature tolerance and optimal temperature.

Basil is one of the most popular herbs in the world. Its popularity is not just because it’s famous in the kitchen but also because it grows in many different climates.

This herb is native to tropical regions, particularly Southeast Asia and central Africa. Today, it’s widely cultivated in temperate climates, such as the Mediterranean region.

That doesn’t mean the productivity of basil is the same in all climates where it can grow, though.

Each herb has an optimal temperature at which it grows best. And you can harvest it several times per season.

Temperature is an essential factor in growing an herb such as basil, which we are known to consume in significant quantities.

In this guide, we will look at basil’s temperature tolerance. Then, we will shed light on its optimal temperature range.

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Basil’s Temperature Tolerance

Let’s consider the “temperature tolerance” of a plant. First, we must look at its reaction to extreme temperatures.

The Plant’s Temperature Tolerance

Basil Plant

Since basil grows in tropical climates, it’s logical to conclude that it grows well in hot weather.

Actually, this plant can thrive in sweltering temperatures, and it grows amazingly well up to 90°F (32°C).

But this herb does not do well in cold weather. It can be immediately damaged by a temperature less than 50°F (10°C).

Some basil varieties, or “cultivars,” can grow in cold temperatures around 43°F (approximately 6°C).

Avoid growing your basil in cold climates; it’s better to play it safe. Always aim at keeping the temperature warm enough.

Optimal Temperature

You want the best harvest of basil every time you grow the plant. My advice is always to try to maintain optimal growing conditions.

Many professional gardeners have figured out the optimal temperature range for basil. In an ideal world, you would always keep your plants at around 72.5°–82.4°F (24°–28°C).

You can harvest basil in bulk up to five times each season at this temperature. And if you’re growing it year-round, you’ll be harvesting it numerous times.

Temperature Difference Between Day And Night

Green fresh basil

The story doesn’t end there, though. The temperature fluctuation between day and night is essential for basil’s growth.

You can try to grow several different herbs at a constant temperature. But, for most of them, it will only stunt their growth.

Most plants, including basil, are sensitive to day-night temperature differences. That is what we call a “thermoperiod.”

Scientists are conducting several experiments on the subject. The temperature should drop to between 64.5° and 71.5 °F (18°–22°C) at night.

That will allow for basil to grow best. It will also encourage the plant to amass a high concentration of flavorful and beneficial oils.

Temperature Tolerance Of Basil Seeds

Close up of basil seeds that have germinated on moist water soaked kitchen towel

The temperature tolerance range for basil seeds is close to the plant’s tolerance. The germination of basil is another story. 

The temperature tolerance for seeds isn’t a helpful indicator in this case.

It is much more important to know the optimal temperature. Being armed with that information will help you avoid losing time, effort, and resources.

Basil seeds germinate best at a temperature between 73° and 81°F (22.7° and 27.2°C). You will get the quickest germination at around 79°F (around 26°C). The temperature at night should also drop by 10°F (or 5°C).

At their optimal temperature, seed germination can take only one week and could be up to 90% successful.

What Happens To Basil At Low And High Temperatures?

Here’s how you can know if the temperature suits your basil.

Just know, in some cases, you may be unable to save the plant if it has been attempting to grow at an inconvenient temperature.

At High Temperatures

Fresh Basil ready to harvest

Herbs find it stressful when exposed to too much heat. They must fight to keep their water inside against the force of transpiration.

That makes the herb unstable, putting it at a higher risk of attack by pests and diseases. It is easier for these pests and diseases to invade your basil’s leaves, roots, and stem when your plant is weaker.

In many other cases, basil will start wilting in hot weather and die if a critical number of its cells die.

At high temperatures, seeds will take much longer to germinate. Their germination rate will be as low as 50%.

At Cold Temperatures

Basil

Cold weather stunts basil. Cold temperatures will cause its leaves to start deforming and turning black. This behavior indicates that the cold water circulating inside the plant is damaging the cells.

Basil will also become more susceptible to diseases. This happens because its cell walls become more sensitive and fragile.

In time, and at lower temperatures, the basil sacrifices its foliage and stems to the cold weather, and it will die back to the ground.

The temperature may decrease below its optimal range. If that happens, the basil seeds’ germination rate will follow suit. Sooner or later, the temperature will reach zero, a very low degree.

How Can You Save Your Basil In Such Situations?

Underwatered Basil

Immediately transfer your plant from its environment to a warmer or colder one. It all depends on whether it was frost or heat that injured it.

In case your basil is growing in hot weather, water it sufficiently. Watering it will help to avoid dehydration and restore stability.

But the action will differ if your basil is growing in cold weather. Remove all the damaged leaves. Then, transfer the plant to a container with warm potting soil.

In all cases, prevention is best. Always track the temperature where your basil is growing.

Moreover, avoid keeping the plant in extreme weather, even if only for a few hours.

Conclusion: Basil Loves Warm Temperatures and Hates Cold

To sum up, the temperature tolerance of basil leans to the warm side. This herb hates cold weather (anything less than 50°F [10°C]) and will die in frosty conditions.

It’s always preferable to grow this plant in an optimal temperature range (72.5°–82.4°F [24°–28°C]) for the best harvest.

Enjoy growing your basil, and don’t forget to share your thoughts and inquiries in the comments below!

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Jad Daou

Jad has always been passionate about growing plants. When he finished high school, he majored in biology, which makes him very knowledgeable about agriculture.