A yellow leaf has lost its chlorophyll (pigment) and it can't turn green again even after you correct the problem. Don't worry, if the plant regains its health, it's possible that new leaves will fill in during the next growing season. Growing plants is always a matter of patience.
Irregular yellowing with potential leaf deformities is usually caused either by a pest or a mineral deficiency. If no pests are visible, then this is likely caused by a mineral deficiency, usually calcium or boron. The solution = fertilize once a month, or repot your plant to provide fresh potting soil.
Nitrogen deficiency shows up as a general yellowing. Older, inner leaves turn yellow first. As it progresses, yellowing moves outward, eventually reaching young leaves, too.
Apply a liquid fertilizer containing iron or Liquid Iron, though it may leave a rusty residue on the leaves. This is only a temporary solution. Adjusting the soil pH is another option. Applying sulfur will lower the pH, allowing the iron to be more available to the root system.
Below are six signs you can easily recognize to determine if you are giving your plants too much fertilizer: Yellowing and wilting of lower plant leaves. Browning of leaf margins and tips. Black brown or rotting roots.
Overwatering
Watering issues are generally the most common cause of yellowing leaves.
Determine which by feeling the leaf showing browning: if it feels crispy and light, it is underwatered. If it feels soft and limp, it is overwatered. Yellowing leaves: Usually accompanied by new growth falling, yellow leaves are an indication of overwatering.
Nitrogen deficiencies cause lawns and the leaves of plants to turn a yellowish or bluish-green color if the soil nitrogen is not consistently replaced through the application of fertilizer.
Plants need light, but too much of a good thing can affect your plant's health and cause leaves to turn yellow. Sunburn may cause dark burn-like spots on leaves or can cause full yellowing of leaves receiving too much sun.
Yellow leaves all over your houseplant can also mean that it has pests such spider mites or a bacterial disease. If bugs are pestering your plant, put it in the shower and spray off all the leaves. Then, let the plant dry off before treating it with neem oil or insecticidal soap ($8, The Home Depot).
Best synthetic fertilizer for flowering plants
Nitrogen is to make green stuff like stems and leaves.
Some bounce back quickly, others languish and may never be the same. Read my guide to fixing overwatered houseplants to help fix this problem. If the overwatering problem is caught early, then the yellow leaves may turn green again, but if the damage is significant, then these leaves will continue their demise.
You may see some yellow leaves and some leaf drops in late summer. A few yellow leaves falling in summer doesn't automatically mean your tree is in trouble. For example, a tree may drop insect-damaged or diseased leaves if they no longer produce food energy for the tree by photosynthesizing.
If your plant's leaves are turning yellow, it might have a sulfate deficiency. If your plant's leaves are turning yellow but the veins remain green, it might have a magnesium deficiency. Epsom salts are a great solution for both of these problems.
Nitrogen is used by plants for lots of leaf growth and good green color. Phosphorous is used by plants to help form new roots, make seeds, fruit and flowers.
For Leafy Greens
An organic, high nitrogen, organic fertilizer like E.B. Stone Organics Blood Meal is perfect for helping your lettuce greens grow tons of leaves. Don't use it on your other vegetables, though. You'll end up with leafy tomato plants and hardly any fruit.
Some plants may yellow as they struggle to find bright enough light to keep producing the chlorophyll that greens up the leaves. “Indirect light doesn't mean a dark corner—brighten it up! You're much less likely to be able to save the leaf itself,” she says.
There are a number of reasons a plant's leaves will turn yellow. Among the reasons are overwatering, underwatering, stress caused by temperature changes, soil conditions, lack of proper nutrients, pests, disease, the age of the plant, pot-bound roots and transplant shock.
Identification. Slow growth and uniform yellowing of older leaves are usually the first symptoms of nitrogen (N) deficiency. Nitrogen-deficient plants produce smaller than normal fruit, leaves, and shoots and these can develop later than normal.
Epsom Salt for Plants
Aside from the anecdotal evidence about human benefits, Epsom salt does seem to help plants. Generations of gardeners have said it helps their plants grow bushier, produce more flowers and have better color. It's also said to help seeds germinate and repel slugs and other garden pests.
There may be entire patches of yellowing leaves, and if you look closer, you may get a look at the pest itself. The most common pests are aphids, whiteflies, scaly bugs, spider mites, and thrips. The majority appear as tiny winged bugs, while the others may resemble scales or fluff.