December 2007

Crop Culture Report: Hibiscus Klahanie Series By Judy Born

Klahanie hibiscus are a vegetative, florist-quality hibiscus. They are "own root" hibiscus that produce huge flowers in a wide variety of colors. Many of the varieties have double or semi-double flowers.

Northern Innovators has promoted this new series for the past two years, and the crop itself is just entering its third year of commercial production. Klahanie hibiscus is a series of seven double-flower forms with nine single-flower forms. Five colors were introduced this year (two doubles and three singles) with three new colors (one double and two singles) on the way for a 2008 debut.

Scheduling

Hibiscus are hard to root, which is why they are available only as rooted liner or "prepinched" large plugs. Once you receive your liner, plant up into the finished container size. Plants require one pinch, but two pinches will provide an optimum bushy plant. Finish timing from a liner is 18-21 weeks and 10-13 weeks from a "prepinched" large plug.

Most hibiscus are aggressive growers. Klahanie varieties have a bit more controlled growth and do not require heavy growth regulators. A light application of Cycocel (chlormequat chloride) once finished height is achieved will control this series of hibiscus.

Culture

Hibiscus do not like "wet" feet, nor do they like to be overly dry. Maintaining the correct moisture level is essential to an overall good bloom count and relates directly to the size of the bloom.

High light and long days help the plant produce a good crop of flowers. Light intensity is the key for the best bud set.

Tropical hibiscus require a minimum of 68¡ F nights. Optimum day temperatures range from 68¡ to 85¡ F. Lower temperatures delay bud development, and the plant effectively stays dormant.

Fertilizers and PGRs

The prevailing opinion is that hibiscus neither need nor want high amounts of phosphorus (middle number), but they do demand high quantities of potassium (last number). Tropical hibiscus fertilizers have ratio numbers such as 9-3-13, 10-4-12, 12-4-18, and 20-8-20 plus magnesium. A slightly acidic soil with a pH of 6.5-6.8 helps the plant absorb the nutrients.

A phosphorus buildup or pH imbalance accounts for about 95 percent of the cases of slow decline and eventual death in hibiscus. Phosphorus affects bloom quality and quantity, but hibiscus need only a small amount because they "store" phosphorus. Excessive phosphorus will bind up other minerals, and the effect can prove toxic to the plant.

Growth regulators for Klahanie hibiscus are required only once finished height is achieved. This series is more sensitive to PGRs than other types of hibiscus. Suggested PGR and rates for Klahanie hibiscus is Cycocel at a rate of 45 mL per 8 liters of water for the less vigorous varieties with the highest rate to be a combination of Cycocel at 90 mL per 8 liters of water with Bonzi (paclobutrazol) added at 5 mL per 8 liters of water for the most vigorous varieties.

Pest Management

Bacterial leaf spot, fungal leaf spot, white flies, spider mites, aphids and snails are among the enemies of hibiscus. Check frequently for insects such as aphids, thrips, scale, whiteflies and spider mites. Water plants thoroughly before using insecticides to lessen the shock. It's usually best to apply in the early morning or in the evening, when temperatures are below 80¡ F. Both the tops and undersides of the leaves should be finished when applying the insecticide. Hibiscus growers should enforce zero tolerance for spider mites: Using chemicals in combination that kill both the parent and eggs are the best.

Bud Drop

Notice buds dropping excessively? Bud drop is a sign of stress. It is occasionally a problem, especially with double-blooming varieties during excessively hot weather. Some hibiscus cultivars are more sensitive to heat and seem to drop buds almost naturally under these conditions. Hibiscus grow best in daytime temperatures ranging between 75¡ and 85¡ F.

Not all bud drop is caused by excessive heat, though. Any stressful condition can prompt the plant to drop its buds. In many cases, the cause is one of the following: lack of water, excessive water, wind, heavy rain, insects (especially hibiscus midges or thrips) or unbalanced feeding formula. Try moving the plants into a shadier area and regulating the watering more closely.