One of the most commonly grown garden plants, tomatoes are quite sensitive to both cold and too much sun. Because of their extremely long growing season, many people start their plants indoors and then transplant later in the growing season once the soil has consistently warmed. The transplantation of the tomato seedlings is where one may run into a problem. Their susceptibility to temperature and light extremes often renders them vulnerable to white tomato leaves. Let’s explore this white leaf color on tomato plants.
Why Do Tomato Leaves Turn White?
If you’re unlucky enough to find a silver or white leaf color on your tomato plants, it is undoubtedly the result of either sun damage, cold vulnerability or some sort of disease (most likely fungal).
The most common cause of leaves turning white in tomatoes, especially young seedlings that are recently transplanted, is exposure to intense sunlight. Although tomato plants need full sun for healthy growth, a sudden change of venue from indoors to outdoors may shock the plants and cause the tomato leaves to turn white. Generally, the damage from sunlight appears as a border of white leaf color on the tomato plant. The leaves may curl and break, leaving minimal foliage on the plant. Winds in the area of transplantation exacerbate this condition as well. Mature tomato plants suffering from sunscald will include blistered or papery fruits.
The solution to tomato plants with white leaves due to sun over exposure is simple in retrospect. In the future, allow the transplants to languish in the shade for a few days and/or move them outside on a cloudy day, then gradually place them in the sun for a couple of hours each day over the course of one or two weeks. This is called hardening off. Either of these gives the plant time to acclimate to its more radical environs.
If hot, dry winds are an additional issue, try placing a windbreak around the transplants, or relocate to a protected area. With either issue, if the windburn or sun scorch is not severe, the plant will likely recover; remove any afflicted leaves to discourage disease.
Fungal Reasons for Tomato Plants with White Leaves
Other than environmental exposure, another explanation for tomato plants with white leaves is disease. Primarily the disease is fungal in variety and resulting from the same cause, overwatering. Too much water in the soil stimulates the fungal spores and causes root rot, Alternaria or Septoria leaf spot, which has dark borders surrounding the white blotches on the leaves.
Transplants should be watered deeply for the first three days and thereafter, dependent on your climate, once a week to every two weeks. This promotes deep root development and deters fungal spores from taking hold. If a fungal disease has taken root, so to speak, try a fungicide made for use on tomato plants to repair any leaves that are turning white on your tomatoes.
Nutrients Causing Leaves Turning White in Tomatoes
Lastly, a potential cause of the leaves turning white in your tomatoes is a lack or surplus of nutrients. Plants lacking nitrogen or phosphorus may show whitening or yellowing of their leaves. A tomato fertilizer containing the proper amounts of these nutrients is a likely solution.
Additionally, deficiencies of calcium or magnesium will also cause whitening of leaves with the leaf veins retaining their green hue. Again, an application of the proper fertilizer is in order. Additionally, garden lime will aid in the calcium deficiency.