Basil Plant Leaves & Stem Turning Black – What to Do

Are the leaves and stem of your basil suddenly starting to turn black? The blackened appearance of a basil plant can be caused by a number of factors, such as changes in the environmental condition. It’s important to take care of these factors as soon as possible if you wish to save the basil plant.

The Basil Plant Has an Infection

Do you notice dark spots forming along the leaves of the basil plant? This could be due to an infection called bacterial leaf spot. This infection is known to develop in wet, cool conditions. In addition to the black spots, the basil leaves may also look more delicate.

The bacterial leaf spot infection can be stopped if you identify it an early-enough stage. Once the conditions around the plant becomes dry, carefully remove all the infected leaves and also remove any dead leaves on the potted soil.

You are Over-watering the Plant

Over-watering may also cause the basil plant to eventually develop black leaves. The roots of the basil plant start to get clogged if there is too much moisture lingering around in the soil. This is why it’s important to use well-draining soil for houseplants.

In the worst case scenario, your basil plant may already be affected by diseases like root rot. The blackened appearance of the basil leaves could be due to the roots not being able to absorb the nutrients the plant requires from the soil. If it’s still at an early-enough stage then we suggest to carefully remove the affected roots and to transplant the basil plant to new, well-draining soil.

Room Temperature is Too Cold

Basil plants can actually be quite delicate. They can get easily damaged if they experience the slightest of frost. If you notice the edges of the basil leaves starting to blacken first then it could be due to a change in temperature.

The optimal temperature for basil plants is somewhere between 72.5°–82.4°F (24°–28°C). We suggest to maintain a temperature as close to this range as possible, especially as the winter season kicks in. Basil plants love full sun so placing them next to the a south-facing window may also help.


  • Mary-Kay:

    The leaves of the plant turn black on the bottom. This is the 2nd pot that did this. They were in opposite sides of the garden.the black stuff grows on the bottoms of the leaves. The first 2 plants in a pot died. The ones today have turned and I was told to get rid of them and the soil cause the black mold is toxic – is this true?

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