Basil Displaying Brown Tint on Edges of Leaves
Answered by: Inge Poot
Question from: M. Hack
Posted on: July 22, 2005

My basil is doing great up until today, when I noticed that some of the leaves have a light brown tint on the edges. Other than that the basil is doing fine. Any ideas?

Bright light will give leaves more purple anthocyanin pigment and if the extra pigmentation is slight it will look brown. I expect that the plant is in excellent light and as long as the edges don’t become crisp and brown, in other words, dead, don’t worry.

If they do die off, then the plant is under water shortage stress. This can have several causes.

Over-fertilizing causes water to be pulled out of the roots and some will die and then the plant cannot take in enough water to keep up with evaporation needs for cooling and other internal processes. The first place to show the damage will be the points furthest removed from the veins, in other words the edges.

A sudden heat wave can catch the plant unprepared with sufficient roots to keep up with evaporation and again the edges die first.

Waterlogged soil can suffocate the roots and then the plant cannot take up enough to keep up......

Or a disease has gotten into the root area and every time the soil is moist the fungi or bacteria attack and kill more roots..... Some diseases multiply very rapidly in hot weather and others in cool weather.

If the soil around the roots has been allowed to become bone dry then first the fine roots and in prolonged cases also the thicker roots are turned into hay. So until new roots have regrown, the plant cannot take up any water and turns to hay and then mush on the now wet soil. This scenario is very hard to distinguish from overwatering, because the end result is identical. You have to try to honestly remember if the plant ever dried out or not.

In excessive heat (a factor during the 2005 North American summer) shading and timely watering are very important. The smaller the pots are that the plants are in, the harder it is to keep the moisture level just right and the harder it is to keep the pot itself from becoming so hot that it bakes the roots to death. In this case clay pots and good air movement help to increase evaporation at the root level and thus keep the temperature lower. However plants like basil that thrive in heat will dislike clay pots as soon as it turns cool in the fall!

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