The passion fruit plant is a vine that has dark green leaves with three points on each leaf and purple or yellow fruit. The passion fruit vine is native to South America, but also grows well in many Southern United States locations. The passion fruit plant has fewer problems than many other plants, but also typically has a shorter life span (around seven years). One of the few problems that the plant does face is the potential for the leaves to turn yellow and fall off.
One of the most common reasons that a passion fruit plant will have yellow leaves is when the soil surrounding the vine is too dry. Passion fruit vines require more water than many people give them, considering that they are a warm-weather plant. The soil should never be allowed to dry out completely. Watering should be done at least twice a week. When passion fruit is nearing maturity, more frequent watering may be necessary. Test the soil every day for dryness. If you can feel some moisture in the soil, then the vine does not need watering.
Lack of Nutrients
Passion fruit vines consume a lot of nutrients over their short life span. This means that frequent fertilizing is necessary to keep the plant in optimal health. If the vine does not receive enough nutrients, the leaves can yellow and the plant will look sickly. Essential nutrients for passion vines include: phosphorus, nitrogen, potassium, magnesium, iron, manganese, zinc and copper. A fertilizer containing these ingredients should be applied to the plant, starting around February or March, and continuing every four to six weeks until September or October.
The woodiness virus can cause the leaves of the passion fruit plant to yellow. Signs of the woodiness virus include: crinkled leaves, yellowed leaves, scabby fruit and mottled foliage. There is no way to control this virus or to prevent it from harming the plant. The only way to treat the woodiness virus is to remove the infected plant and destroy it immediately. That way the virus cannot spread to other plants.
Grease spot can cause small yellowish spots to appear on passion fruit leaves. The grease spots have yellowish-green centers, with a yellow ring surrounding the spot. Grease spot will cause the leaves to fall from the vine and fruit to drop before it is ripe. The best way to prevent this disease is to water the plant in the morning and reduce nitrogen levels in fertilizer. Grease spot can be treated with an application of metalaxyl + copper oxide.
Passion fruit vines are susceptible to freezing. If the plants freeze, their leaves will likely turn yellow and fall off. The only way to prevent freezing is to cover the plant during freezing temperatures. Fortunately, the passion fruit vine generally grows back each spring even if it froze over the winter.