Basil is one of the most popular herbs in the world 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, but today it’s widely cultivated in temperate climates, such as the Mediterranean region.
That doesn’t mean, however, that productivity of basil is the same in all of the climates in which it can grow.
In fact, each herb has an optimal temperature at which it grows best and can be harvested several times per season. This is very important for growing an herb such as basil, which is consumed in great quantities.
In this article, we will take a look at the temperature tolerance of basil, while shedding light on its optimal temperature range.
Basil’s Temperature Tolerance
When we consider the “temperature tolerance” of a plant, we should look at its reaction to extreme temperatures.
The Plant’s Temperature Tolerance:
Since basil grows in tropical climates, it’s logical to conclude that it grows well in hot weather. Actually, this plant can thrive in very hot temperatures, and it grows amazingly well up to 90°F (32°C).
On the other hand, this herb does not do well in cold weather. It can be immediately damaged by a temperature less than 50°F (10°C).
Some varieties or “cultivars” of basil, though, can grow normally in cold temperatures around 43°F (approximately 6°C).
To play it safe, it’s better to avoid growing your basil in cold climates and always aim at keeping the temperature warm enough.
If you want the best harvest of basil every time you grow the plant, you should always try to maintain optimal growing conditions.
As for temperature, many professional gardeners have concluded that the optimal temperature range for basil is around 72.5°–82.4°F (24°–28°C).
At this temperature, you can harvest basil in bulk up to 5 times each season, and if you’re growing it year-round, you’ll be harvesting it numerous times.
Temperature Difference Between Day and Night:
The story doesn’t end there though. The fluctuation of temperature between day and night is essential for the proper growth of basil.
If you try to grow several different herbs at a constant temperature all the time, most of them will be stunted because most plants, including basil, are sensitive to the difference in day-night temperature or what we call a “thermoperiod.”
According to several experiments, the temperature should drop to between 64.5° and 71.5 °F (18°–22°C) at night for basil to grow best and accumulate a high concentration of flavorful and beneficial oils.
Temperature Tolerance of Basil Seeds
Although the temperature tolerance range for basil seeds is close to that of the plant, the germination of basil is another story.
In fact, the temperature tolerance for seeds isn’t really a useful indicator in this case. Knowing the optimal temperature is much more important to 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 a temperature of around 79°F (around 26°C). The temperature at night should also drop by 10°F (or 5°C).
At their optimal temperature, germination of seeds can take only one week and be up to 90% successful.
What Happens to Basil at Low and High Temperatures?
Here’s how you can know if the temperature is suitable for your basil, although in some cases you may not be able to save the plant after it was attempting to grow at an inconvenient temperature.
At High Temperatures:
Heat is stressful for herbs as they fight to retain water inside them against the force of transpiration.
That makes the herb unstable and puts it at a higher risk of attack by pests and diseases, which find it easier to invade the leaves, roots, and stem of your basil.
In many other cases, basil will start wilting in hot weather and eventually pass away if a critical number of its cells die.
At high temperatures, seeds will take much longer to germinate, and they will have a germination rate as low as 50%.
At Cold Temperatures:
In cold weather, basil will be stunted, and its leaves will start to deform and turn black, which indicates that the cold water circulating inside the plant is damaging the cells.
In this case, basil will also become more susceptible to diseases as its cell walls become more sensitive and fragile.
Eventually and at lower temperatures, basil will die back to the ground as it sacrifices its foliage and stems to the cold weather.
The germination rate of basil seeds will start decreasing as the temperature falls below the optimal range until it reaches zero at a very low degree.
How Can You Save Your Basil in Such Situations?
Immediately transfer your plant from its environment to a warmer or colder one, depending on whether it was hurt by frost or heat.
In case your basil was growing in hot weather, water it sufficiently to avoid dehydration and restore stability.
On the other hand, if your basil was growing in cold weather, remove all the damaged leaves and transfer the plant to a container that contains warm potting soil.
In all cases, prevention is best. Always monitor the temperature where your basil is growing, and avoid keeping the plant in extreme weather, even if only for a few hours.
Summary & Conclusion: Basil Loves Warm Temperatures and Hates Cold
To sum up, the temperature tolerance of basil leans to the warm side. In general, 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 at 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!