July 2003

Hibiscus moscheutos ‘Pyrenees Pink’ By Paul Pilon

Hardy hibiscus is an old-time garden favorite riding a new wave of popularity. Hibiscus moscheutos is a marshland native of the eastern United States and has hardiness in USDA Zones 4-9. With new developments in plant breeding, today’s hibiscus cultivars offer improved flower sizes and colors, more appealing plant habits and extended bloom times.

Gilberg Farms has introduced dozens of improved hardy hibiscus cultivars to the marketplace, such as ‘Pyrenees Pink’ with bigger, brighter blooms that last from midsummer to frost. Pyrenees Pink is a superb cultivar that produces loads of hot pink flowers that measure 10-12 inches. It withstands a variety of environmental conditions, including poor soils and drought. Plants are very cold and heat tolerant, withstanding temperatures of -25¡ F to 100¡ F. Pyrenees Pink is vegetatively propagated by tip cuttings. Propagation without a license is prohibited, as it is a patented variety.

Production

Many growers will receive their hibiscus plugs early in the season before they have broken dormancy. Quite often, they will appear as sticks protruding from the soil and showing very few signs of life or potential growth. Upon receipt, unpack the liners and water them thoroughly. If planting does not occur immediately, keep the liners moist until they can be planted. Place them in a greenhouse or outdoor bed that provides lots of light and ambient temperatures.

After transplanting into their finished container, grow hibiscus at warm temperatures, ranging between 70-80¼ F. Warmer temperatures will result in short crop production times, whereas cooler growing conditions (less than 68¡ F) will cause longer production times and the leaves will usually appear chlorotic. Hibiscus thrives under high light levels and should be produced in full sun or in structures with no shading material. They are obligate long day plants and will not flower unless they receive a minimum of 12 hours of daylight. In Michigan, flowering under natural conditions will occur from late July to frost.

Pyrenees Pink grows very rapidly and should be produced in a large enough container to accommodate this growth. For this cultivar, I recommend planting a 21/2-inch liner into a 2-gal. container. To help promote lateral branching, pinch the hibiscus, retaining 4-6 leaves on each branch. Pinching will provide more branches, more flowers and a fuller plant. From pinching, expect 5-6 weeks to reach flowering. Take notice of your desired sales period and try to schedule pinching accordingly.

The finished container should be filled with a medium that drains well but retains water. If plants are produced in outdoor locations, a medium containing sand will provide weight, which helps prevent pots from being blown over by ç the wind. Media pH should be maintained between 5.5 and 6.5.

Pyrenees Pink requires consistent moisture levels and should never be allowed to wilt. Allowing them to wilt could result in lower leaf yellowing and even flower bud abortion. I recommend, when watering is required, to water thoroughly and allow the substrate to dry slightly between waterings. Once established in the landscape, hibiscus is considered drought tolerant.

Hibiscus are heavy feeders requiring a controlled release fertilizer incorporated at a rate equivalent to 1-11/2 pounds of nitrogen per yard of growing medium. Due to the frequency of irrigation and the volume of water applied, I find it is better to rely on a controlled release fertilizer program over a constant liquid fertilizer program. However, if a liquid fertilizer program is implemented, feed plants weekly at 150-200 ppm nitrate from a complete fertilizer.

When producing Pyrenees Pink in containers, it is often necessary to control the plant height. There are several options available. Pinching can be an effective method of keeping your plants smaller. Multiple pinches per crop are acceptable, provided you leave adequate time for plants to reach flowering before sales.

Even with pinching, I have found it necessary to use chemical plant growth regulators. Growers commonly spray multiple applications of a tank mixture of B-Nine at 4,000 ppm and Cycocel at 1,000 ppm or Sumagic alone at 10 ppm over their hibiscus crop. Some growers have found applying Bonzi at 5 ppm as a drench twice during the production cycle to be an effective method of controlling the height of hibiscus.

Pyrenees Pink generally does not have many insect or disease pests. I have observed aphids, thrips, spider mites, whiteflies and Japanese beetles feeding on hibiscus at times. It is not necessary to implement a preventative program unless these insects are always a nuisance at your operation. Upon early detection, these insect pests are easily controlled with various insecticides currently available. Diseases of hibiscus include Rhizoctonia, Alternaria leaf spot and Cercospora leaf spot. These diseases can be controlled with bi-weekly applications of copper based fungicides such as Camelot or Phyton 27 and broad spectrum fungicides such as Cleary’s 3336, Sextant or Spectro 90.

Forcing

Growers usually receive dormant plant material or plants that have just recently come out of dormancy. If planting actively growing plants, I recommend pinching the growing points, leaving at least four leaves on the stem. Otherwise, pinch the dormant material a couple weeks after it breaks dormancy and is actively growing. I have found that it is beneficial to pinch a second time for aesthetic reasons. The second pinch usually occurs three weeks after the first. It will take 6-8 weeks from the last pinch to reach flowering when grown under the following conditions. To supply plants in bloom for later sales periods, pinching can also be used as a method to delay flowering,

As mentioned previously, Pyrenees Pink is an obligate long-day plant and must be grown under long-day conditions to flower. Long-day conditions can be achieved by ensuring a minimum of 16 hours of light or by providing natural days plus a 4-hour night interruption.

The biggest factor to finishing a crop of hibiscus is temperature. Warm temperatures are highly recommended and will dramatically decrease the production time needed to lower this crop. Provide a minimum average temperature of 72¼ F. At this temperature, it will take 10-12 weeks, from start to finish, to produce a crop of Pyrenees Pink. Warmer temperatures such as 80¼ F will finish a crop of flowering hibiscus in as little as eight weeks.

Availability

This patented plant can be purchased directly from Gilberg Farms or through various reputable brokers.