Sickly, yellow leaves on your favorite plant may entice you to
go running for the pesticide spray. But before you start spraying
haphazardly, take a moment to try to diagnose what precisely is
wrong with that plant.
Sickly, yellow leaves on your favorite plant may entice you to go running for the pesticide spray. But before you start spraying haphazardly, take a moment to try to diagnose what precisely is wrong with that plant.
While yellow leaves may, indeed, mean an attack from a pest, they also could be caused by a number of other factors. Here they are:
1. Too much water. Overwatering causes yellow leaves because too much water prevents oxygen from getting to the plant’s roots, thus smothering them. As roots die, the foliage above the ground often will discolor and die.
Overwatering can be corrected pretty simply: apply less water. You can also improve drainage by mixing in organic compost or soil conditioner into the soil.
2. Lack of fertilizer. Yellow leaves also can be symptoms of a form of chlorosis, or lack of iron or other forms of nutrients. Lack of iron is often seen in light green leaves and, worse, yellow leaves or yellow-veined leaves.
Iron-deficient soil can be corrected by applying an iron chelate fertilizer evenly over the surface and watering it in. Iron can also be sprayed onto the foliage as a liquid fertilizer. Be careful about using iron chelate, though. I’ve had friends kill a citrus tree by overfertilizing with iron.
3. Wrong location. Shade-loving plants that are getting too much sun, such as hydrangeas and fuchsias, will often start to turn yellow. Sunburn isn’t something only people get by falling asleep with their hand across their stomachs. (I’d had fingerprints on my stomach for the past three months!) Plants will also get sunburn, and it shows up in the areas between the veins of the foliage. It appears as a yellow or brown area, and then the foliage begins to die in that area. A combination of too much sunlight and heat, and not enough moisture, will cause sunburn.
The best prevention for sunburn is to choose plants that are suited for the site. Don’t put shade-loving plants in too much sun, or vice-versa.
4. Garden pests. No, I’m not talking about the neighbor kid who keeps kicking their soccer ball into your beloved lace-leafed Japanese maple. Instead, I’m talking about insect infestations that could, indeed, cause yellowing of leaves. Take a close inspection of your yellowing leaves and, if necessary, put a sample in a plastic baggy and take it to your nearest garden center for a diagnosis.
Sometimes yellow leaves could be the work of insects. However, more often than not, they’re caused by overwatering, lack of fertilizer or too much sun. No matter what the cause of yellow leaves, there is a solution. Just be careful about how you treat the problem before knowing what the cause is.
