Hibiscus plants are flowering shrubs. Most commonly grown hibiscus plants probably are hybrids, according to the University of Florida IFAS Extension. Hibiscus plants are desirable for their colorful flowers and beautiful appearance, but they are not the easiest plants to grow, and can suffer from a number of problems. Some of the problems are preventable or treatable, while others are more serious to the plant's health.
Chewing and sucking insect pests are a problem with hybrid hibiscus plants. Mealybugs, aphids, caterpillars, snails, and even grasshoppers, along with several other common insects, can destroy both the leaves and the flowers of the plant. While unattractive, this usually is not life-threatening to the plant.
In general, these insects can be controlled by applying a pesticide to the plant, according to the University of Florida--whether as a preventative measure in the spring or upon noticing insect activity around and on the plant. Follow the directions for applying the pesticide according to the label on the product, and the size and age of your hibiscus.
Fungal diseases are common. Cankers are fungus growths that invade the wood and can cause the branches or entire plant to die. Root rot occurs when fungi in the soil attack and destroy the hibiscus roots. This usually is signified by the plant slowly starting to wilt all over. Fungi borne on rain or splashing water can develop on the leaves and cause unattractive spots to develop.
Prevention is the best way to control fungal diseases. Water at the soil level to avoid getting water on the leaves, and give your plant plenty of room for air to circulate. Plant hibiscus shrubs in well-draining soi,l and make sure they are not over-watered. Standing water or very soggy soil should not be allowed to develop. Wood that is affected by cankers (orange, sometimes seeping areas on the wood) can be pruned off. You also may spray your shrubs with a fungicide in the spring before bud break.
According to North Dakota State University, bud drop is a common complaint of hibiscus owners. Environmental changes can cause this, such as over- or under-fertilizing, or moving the plant to a new location. Potted hibiscus plants are sometimes placed by a draft, which often causes buds to drop, or they are brought indoors for the winter. Indoor air is much drier than outdoor tropical air, and this causes bud drop.
In general, hibiscus plants are affected by change, so the best way to avoid bud drop is to keep their care needs consistent. Don't move them around, and make sure to maintain steady levels of sunlight, water, fertilizer and humidity.