Plant Answers

Hibiscus

Chinese, or Evergreen Hibiscus, (Hibiscus rosa-sinensis) offers an excellent source of summer landscape color and is one of our most popular tropical or sub-tropical flowering plants. In recent years, the popularity of hibiscus in Texas even appears to be on the rise, although insects, diseases and the possibility of injury during the winter place limitations on its use. Hibiscus should be grown as a container specimen in most of the state. This allows gardeners to provide the optimum conditions for protecting the plant from diseases and winter damage, and for producing its best blooms and foliage.

Hibiscus belong to the mallow family and are closely related to cotton, hollyhock, turks cap, mallows, shrub althea, confederate rose, and okra. Even in the older hibiscus varieties there is considerable variation in the size and texture of the foliage. Their colors also vary from white through pink, red, yellow, apricot, and orange. The form of their blooms generally is either singled or double.

The American Hibiscus Society was formed in 1950, and thanks to this organization’s work, many new hybrid hibiscus varieties have been developed in recent years. The plants now come in dwarf, semi-dwarf, and other smaller sizes more suitable for plantings and container culture. Their foliage is often much larger, heavier, more glossy, and considerably more interesting in form. Their blooms now range more frequently from 7 to over 10 inches in diameter. Many new miniatures have also entered the picture. The new hybrid hibiscus comes in a myriad of richer colors and forms, ranging from blossoms of gray, brown and various shades of purple, to multicolor blooms with 4 or 5 colors. The petals can range from tufted, crinkled, and frilly single blossoms, through an amazing range of semi-double and double blooms. Also, these new hybrids are usually grafted onto hardy rootstocks so that a more vigorous plant is produced, resulting in the capacity to provide many years of enjoyment.

Hibiscus require about a half-day of sunshine to perform well. Containers should be used with a potting mix consisting of peat moss, perlite, vermiculite, and pine soil conditioner to insure both good drainage and moisture retention. Dolomitic lime should be added so that a pH of about 6.5 to 7 is present in the mix. Hibiscus require regular watering, especially in the afternoon heat. Both a time-release fertilizer and a water-soluble fertilizer, each with minor nutrients, should be used from April through October. The first should be applied about every 6 to 8 weeks as a top dressing and the latter once a week.

Growing hibiscus in containers with a proper potting mix avoids many problems for the gardener. This includes root knot nematode and cotton root rot so frequently encountered with plants grown in soil. Also, in cold weather the plants may be easily moved to a protected situation to avoid freeze damage and destruction.

A frequent cause of concern with older forms of hibiscus is the dropping of buds. This problem is largely eliminated in the newer hybrid hibiscus when they are grown in containers with a proper potting mix and when treated to avoid insects such as thrips or aphids. A regular use of an insecticidal soap or even a mild detergent liquid soap and summer dormant oil is an excellent way to avoid these and other insects.

Most of the older varieties of hibiscus are grown from cuttings. The newer hybrids are almost always propagated by grafting a scion of a variety onto a hardy rootstock much in the way that hybrid pecan trees are propagated. The new hybrids are difficult to grow from cuttings.

The Chinese hibiscus is cold sensitive and MUST be protected from freezing temperatures. The leaves are usually shiny. This is in contrast to the perennial hibiscus that dies to the ground every fall. The top is removed and the plant sprouts again from the underground roots. The perennial hibiscus is root hardy, meaning that it will come back from the root after the top dies. A complete discussion of the root-hardy, perennial hibiscus can be found at:

http://www.plantanswers.com/hibiscus.htm