By Becca Badgett
(Co-author of How to Grow an EMERGENCY Garden)
As a favorite outdoor blooming plant, the mandevilla often gets special attention from the enthusiastic gardener. Some are disappointed when finding yellow leaves on a mandevilla. Following are some answers for the gardening question, “Why are my mandevilla leaves turning yellow?”
Reasons for Yellow Mandevilla Leaves
There are a number of causes to a mandevilla plant turning yellow. Below are some of the most common reasons for yellow mandevilla leaves:
Improper watering can cause yellow leaves on a mandevilla. Too much or too little water can be reasons for yellow mandevilla leaves. Soil should remain moist, but not soggy. If roots are soggy, remove the plant from the container and remove as much of the soggy soil as possible. Repot in fresh soil that is barely moist.
Waterlogged roots are a common reason for the mandevilla plant turning yellow, as is dried out soil. If the plant is getting too little water, leaves will curl as they yellow. Water if necessary. Bottom watering can be effective in this case, as the plant will only take up the water it needs.
Lack of the right fertilizer can also be responsible for yellow mandevilla leaves. If it has been a while since feeding your plant, then it’s likely your mandevilla plant turning yellow is due to a lack of nutrients.
If the mandevilla plant is older, some yellowing leaves are to be expected as they die to make room for new growth. A few yellow leaves on a mandevilla can be removed. When removing the yellowing leaves, take a close look at the rest of the plant, particularly on the underside of the leaves and in the axils of the leaves and stems where insects are common.
Insects can cause yellow leaves on a mandevilla. Mealybugs, spider mites and aphids can weaken plants and are sometimes reasons for yellow mandevilla leaves. If mealybugs have taken up residence on the plant, small spots of white cotton-like material will be visible. This houses the eggs of the mealybug, where hundreds may hatch and feed on the plant.
Regardless of the pest, treating yellow leaves on mandevilla is done effectively with an insecticidal soap spray or a horticultural oil, such as neem oil. Large infestations may require a systemic insecticide when treating yellow leaves on mandevilla.
Until you determine what is causing yellow leaves on a mandevilla, seclude it from other plants so insects or disease do not spread to healthy plants. You can then determine the problem and begin treating yellow leaves on mandevilla.
Sometimes the reasons for yellow mandevilla leaves are from disease pathogens, such as Ralstonia solancearum, the bacterial pathogen that causes Southern wilt. Plants may be fine in cool weather and when temperatures warm, pathogens may be reasons for yellow Mandevilla leaves. Plants with Southern wilt eventually die. All plant material, soil and containers should be discarded to avoid the spread of the pathogen.
Too much sun is often blamed because the gardener does not ask “Why are mandevilla leaves turning yellow?” until temperatures have warmed and the plant has been located in full sunlight.