Basil Leaves Turning Black or Brown? 9 Causes and Solutions

Are your basil leaves turning black or brown? Basil isn’t difficult to grow, but the plants are prone to diseases like downy mildew, sensitive to cool temperatures, and attractive to insects like aphids. Below I outline 9 of the most common reasons for black or brown spots to appear on basil leaves. You’ll also find pro tips to prevent basil problems and learn more about five of the best disease-resistant cultivars to grow to enjoy plenty of fresh basil leaves. Keep reading to learn more about growing great basil.

Don’t panic if you spot a black or brown leaf on your basil plants, because it’s not unusual to see an occasional discolored leaf. The first step is to look closely to see what is happening. Are the blemished leaves at the bottom of the plant? Is the new growth turning black? Are the plants going black from the bottom up? Are the leaves spotted or is the entire leaf discolored? Below I’ll talk about the types of damage we see on basil and explore some of the common reasons for basil plants turning black or brown.

There are a variety of explanations for basil leaves discoloring and some are due to plant diseases, like fungal infections or bacterial infections, while others are related to temperature or moisture.Let’s look closer at some of the issues that can affect basil plants.

Downy mildew, Peronospora belbahrii, is one of the leading reasons for basil leaves turning black. The spores of this water mold are dispersed in the wind, but it can also be transmitted on seeds or seedlings. The first sign of downy mildew is yellowing foliage at the bottom of the plant, but that discoloration quickly