We expect leaves to turn brown, yellow or orange in the fall. However, leaves on both indoor and outdoor plants can also turn brown at any time because the plants need a little extra care.
In the Fall
In the summer, leaves are filled with green chlorophyll, which makes the leaves green too. The leaves use the chlorophyll, along with sunlight, to make glucose they need to grow. This process is called photosynthesis. In the autumn, as the days grow shorter, there is not enough light for photosynthesis. The trees shut down for the winter and the green chlorophyll disappears. The yellow and orange of the leaves now show through. Some leaves also turn brown because of wastes left in the leaves.
A severe early frost can ruin the beautiful colours of fall. Such a frost kills the leaves, turning them brown and causing them to drop early.
Brown Edges on Leaves
Sometimes the whole leaf doesn't turn brown, but just the edges and tips. Brown edges and tips on plant leaves indicate the plant is stressed, usually because it is not getting enough water. You may need to provide supplemental water for plants in the ground or improve the soil with organic material so the soil can hold onto the water better. Plants in containers may need to be repotted so the roots have more room to grow.
Overwatering plants can also cause their leaves to turn brown. Before watering your plants, check if they need water by inserting your finger into the soil about one inch deep. If the soil feels dry or barely damp, then your plant is ready for a drink of water.
Brown Leaf Spots
Brown leaf spots on your plants are usually a fungi that occur when you water with cold water or when water remains on the leaves all night. For house plants, it is best to water with room temperature water. Water indoor and outdoor plants early in the day so the foliage dries before night.
Too much fertiliser can also cause leaves to turn brown. If the leaves of your plants are turning brown, do not fertilise the plants for three or four weeks.