Avoid fertilizing garden plants when the temperatures are above 90 degrees, as fertilizing during the day’s heat with either organic or non-organic fertilizer can cause the leaves to burn. This looks like tan spots on leaves. Gardeners often overfertilize their plants. Too much of a good thing in the form of fertilizer can set your plants back and actually reduce your yields. Signs of over fertilization include brown leaf tips and brown leaf edges as well as copious dark green succulent growth.
Growing Home - Too Much Fertilizer
