Rene Schmit | 5/19/2014 8:01:11 PM
Tropical Hibiscus is a favorite planting for many home gardeners in Louisiana. A primary reason is because tropical hibiscus, Hibiscus rosa-sinensis, produces large, colorful flowers from mid-spring throughout the fall. Certainly, our growing conditions in Louisiana are ideal for growing hibiscus plants. However, as the name suggests, tropical hibiscus are not cold hardy and should always be protected when temperatures fall below 40 degrees. The significant loss statewide of hibiscus plants that were killed this past winter is a reminder of just how tender these plants are.
If planting tropical hibiscus plants in a landscape bed, choose a sunny location that will provide at least six to eight hours of full sun. Direct sun is important for promoting optimum flowering and performance. Keep in mind, the more sun exposure and heat your hibiscus receives especially during the summer months, the more irrigation or supplemental watering it will need. If plants start getting very large by late summer, afternoon shading may slow the watering requirement. The site selected should also be one that provides good drainage. If the soil is heavy with clay, amending the soil with sand, and/or organic matter such as pine bark, peat moss, etc. will be helpful.
If planting in containers, be sure to place containers in an area that provides the same sun opportunity as for in-ground hibiscus plantings. Containers can be placed on a patio, around the swimming pool, along the driveway or in a landscape bed. Containers are an ideal alternative to in-ground landscape planting as container plants can be brought indoors and maintained during the winter in a protected area to enjoy next year. Often the biggest problem with growing hibiscus in containers is drying out. Flower bud drop, sudden foliage decline and excessive yellowing of leaves are symptoms of excessive drying of the soil. Hibiscus planted in container pots will need lots of water during the hottest days of summer. It is also a good idea to include a water-soluble fertilizer with every third watering to replenish and maintain plant nutrients that are leached out due to excessive watering.
Tropical hibiscus needs potassium fertilizer. This is important in addition to a regular source of nitrogen. Use two to three times more potassium than nitrogen. A good fertilizer ratio for hibiscus is a 12-4-18 or a “high bloom” water-soluble fertilizer. Slow-release granular fertilizers, like Osmocote, can also be used in combination with water-soluble fertilizer when watering.
Keep a vigil throughout the growing season for several types of insects that can be serious pests for hibiscus plants. These include thrips, aphids, spider mites, whiteflies, scale and mealy bugs. After positive identification of the insect pest, treat with a recommended insecticide such as insecticidal soap or summer horticultural oil sprays. Realize that when encountering insect pests on hibiscus, more than one insecticide application may be necessary to achieve an effective control. It is best to spray plants at the first indication that an insect pest is present rather than allowing the plants to become heavily infested. Also, spraying of any pesticide should be conducted in late evening and preferably one hour before dark.Rene’ Schmit is the LSU AgCenter County Agent for St. Charles Parish and can be reached at 985-785-4473.