The chemicals that you use to improve the health of your plants can cause serious damage when they are mishandled. Your plants can benefit from the same care in measuring and timing that you would use to measure a child's medicine while you are applying fertilizer, herbicides or pesticides to your plants. There are simple steps you can take to help speed your plants' recovery if they are already damaged.
Discolored leaves and wilted stems are a common sign of a plant suffering from chemical burn. Brown or yellow splotches in the middle of leaves or around the edges of leaves are common signs of a chemical burn. Severely damaged plants may develop curled or malformed new leaves. Severe chemical burns can also cause plants to drop some or all of their foliage. Although chemicals sprayed directly on the leaves of a plant are the usual culprit, chemicals taken up through the root system can also cause burn-like damage on the older, lower leaves of your plants.
Fast-acting fertilizers contain nutrients bound to water-soluble mineral salts. These salts allow plants to immediately draw nutrients up through their roots but leave the salt behind. Using more fertilizer that your plants need can cause salt to accumulate in the soil, preventing your plants from absorbing the water they need. Fast-acting fertilizers that come in direct contact with your plant's foliage can also cause burn-like damage. Slow-release fertilizers release lower concentrations of nutrients for your plants over a period of weeks, but they are less likely to cause chemical burns on your plants.
Applying fertilizer to plants when their foliage is damp is a common cause of chemical burn on leaves. The best time to apply most fertilizers is when the foliage of your plants is dry, the soil is moist and daytime temperatures are below 85 degrees Fahrenheit. Hot weather increases the amount of moisture your plants lose during the day and makes them more susceptible to damage from high concentrations of fertilizer in the soil. Pesticides are more likely to damage your plants when they are under stress from drought; hot and humid weather prevent the pesticide from evaporating. The best time to spray your pesticides is on cool days below 85 degrees F with low relative humidity.
Using the same container to mix and spray herbicides and insecticides seems like a good way to save time, but it can lead to serious damage on your plants. Herbicides can leave a residue behind in sprayer tanks that will cause severe burns and defoliation in plants that you are trying to protect from insect damage. The best way to protect your plants from accidental chemical burns is to use separate sprayers for fertilizers, herbicides and insecticides that are marked and washed after each use.