Showy Tropical Hibiscus

As the hot summer months arrive, I always begin to notice and appreciate plants that really thrive this time of year. For many plants, the hotter and more humid the better. At the end of an extremely humid 95-degree day at work, I am running for the relief and comfort of my air-conditioned home while many of the plants in my garden seem even more beautiful and healthier than ever.

One of the most popular tropical plants that does extremely well throughout our summer, in the garden or in a container on a porch or patio, is the tropical hibiscus, Hibiscus rosa sinensis. Native throughout parts of Asia, you will occasionally see it called the Chinese hibiscus.

The flowers of the tropical hibiscus have always made me think of far-away places and tropical islands. You often see this flower used artistically to represent the tropics on shirts, handbags, beach towels, jewelry, and paintings. Many children’s movies even show fairies that have skirts or dresses that look like tropical hibiscus flowers.

Lush flowers, glossy leaves
The tropical hibiscus flower is quite impressive. It can range in size from 3-6 inches in diameter, be single or double, and be one color or multiple colors, even blue and lavender. The most popular and common flower color is red, but pink and yellow are not far behind, and there are still literally hundreds of other cultivars to choose from. The flower has an almost papery quality, and while each flower does not last long they make up for it by flowering continually.

This shrubby plant has glossy, dark-green leaves that form the perfect backdrop to show off the flowers. The plant can grow anywhere from 4-10 feet tall in the ground in Kentucky, and is generally smaller when grown in containers. While the shrubby form is the most popular, tropical hibiscus can also be found trained into a standard or tree form. The tree form brings a sense of formality to this otherwise very informal plant.

Easy to care for, the tropical hibiscus makes an excellent summertime screen or hedge and thrives in full sun. It is most often planted in containers and grown on decks, porches, and patios. Adequate water is necessary to keep the tropical hibiscus looking its best. Most tropical hibiscus come into our garden center from the grower overly root-bound. This is quite common due to the growing practices necessary to get them lush and ready for retail sales, so transplant them right away in a larger decorative pot once you get them home. Dull, pale-green foliage is a sign of excessive dryness and can be quickly remedied with repotting and adequate water. In other words, the tropical hibiscus is not very drought-tolerant.

Wintering hibiscus
Regular monthly fertilization throughout the growing season will also help keep the foliage glossy green and flower production at its peak. Sensitive to temperatures below 50 degrees, if you choose to overwinter them, it is necessary to bring them indoors by the end of October. It is important to stop fertilizing them at this time, then begin fertilizing them again one month before you take them back outside in the spring.

The lack of humidity and decreased light levels indoors can be stressful on tropical hibiscus, so our goal is to just get them through the winter until it is safe to take them back outside. I am often asked why, once indoors, many of the flower buds just fall off unopened. I suspect it has to do with the lack of humidity and lower light levels indoors. Try increasing the light level with a grow light or put them in the sunniest window possible.

Occasionally, we do see aphids located mainly on the new growth or tips of tropical hibiscus. You can prune out the growth with the worst infestations to physically remove the insect population, and spray the rest of the plant with insecticidal soap, which works very well to kill any remaining aphids.

Every year there are more new and beautiful tropical flowering plants trying to gain our attention. How could we ever get tired of a plant that has such amazing flowers, is so easy to find, easy to grow, and beautiful all summer long like the tropical hibiscus?

ASK THE GARDENER
by Angie McManus

Is there a fertilizer to be used on hydrangeas?

Hydrangeas are one of those old-fashioned plants that are a must-have in every garden. It is best not to fertilize them for the first year. Let them become established in the environment that exists naturally. As long as your plants are healthy, they will benefit from some additional nutrients after they have become established. You can top-dress the existing soil with holly-tone, manure, compost, worm castings, or apply a granulated slow-release, well-balanced fertilizer. For hydrangeas, this means that the three numbers on the fertilizer package should all be the same; for example, 10-10-10.

If you are growing hydrangeas that are either pink or blue and you want to change the color of the blooms, it is best to have your soil tested by contacting your County Cooperative Extension Service. The results will help determine what, if anything, needs to be added since it is possible that the essential elements exist in the soil, but they are not made available to the hydrangeas. Adding lime to the soil will increase the pH of the soil to obtain pink blooms. If blue blooms are what you are after, adding aluminum sulfate to the soil will lower the acidity and help turn your blooms blue.

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Go to www.KentuckyLiving.com, click on Home & Garden, then “Ask The Gardener” link to ask a question.