Luna is a seed propagated hardy hibiscus series that has gained popularity among growers and retailers. The Luna series appeals to container growers, retailers and landscapers because of its compact, well-branched, shrubby habit. It reaches 24-36 inches tall and 24 inches wide and has flowers measuring 6-8 inches across. The series currently contains four colors: ‘Luna Red’ (deep-burgundy red), ‘Luna Blush’ (white with blush-pink rim and dark-red eye), ‘Luna Pink Swirl’ (pink picotee pattern with a dark eye) and ‘Luna White’ (white with large, red eye).
Hibiscus moscheutos is a marshland native of the Eastern United States and is hardy throughout USDA Hardiness Zones 4-9. The plants are ideal for container plantings and landscape uses. Once established, hardy hibiscus withstands a variety of environmental conditions including poor soil and drought. With new developments in plant breeding, the Luna series offers improved flower sizes and colors, more appealing plant habits and extended bloom times.
Starting Luna from seed is relatively easy, as it has a high germination percentage, is relatively trouble free and grows quickly. With its large seed size and fast growth habit, it is best to propagate the Luna series in plug trays with large cell sizes. Most growers sow seeds in 72-cell or larger plug flats. Growers observe better germination and performance when using fresh seed.
Sow a single hibiscus seed per cell in the intended plug flat and cover seeds heavily with a germination mix or medium-grade vermiculite. The seed flats should be moistened and moved to a warm environment where temperatures can be maintained at 68-78º F for germination. To increase the uniformity of the crop, growers can germinate Luna at cooler temperatures (68-72º F) and allow a few extra days for seeds to sprout.
Following germination, continue to grow seedlings at 68-75º F for 5-7 weeks until they are ready for transplanting. Fertilizers are usually applied once true leaves are present. Apply 100-ppm nitrogen every third irrigation or 50 ppm with every irrigation using a balanced, water-soluble source. Keep the growing medium evenly moist, and do not allow the seedlings to wilt.
The series is most suitable for production in 1-gal. or larger containers. When growing 1-gal. pots, one plug per container is generally planted. For larger sizes such as 2-gal. containers, planting multiple plug cells per pot may be appropriate. The Luna series performs best when grown in a moist, well-drained medium with good water-holding capacity. The plugs should be planted so the original soil line of the plug is even with or just below the surface of the new container’s growing medium.
Some growers have found it beneficial to pinch hibiscus prior to or shortly after planting in the final container. This is generally a soft pinch, only removing the growing point of the plant, and should leave 4-6 leaves on each branch. Pinching increases lateral branching and the total number of flowers produced on each plant. Many suppliers Á claim the Luna series branches freely and does not require a mechanical pinch; however, I have found this early pinch dramatically improves the quality of the finished product.
Hibiscus are moderate to heavy feeders. During production the pH of the media should be maintained between 6.0 and 6.5. Growers using water-soluble fertilizers should feed with a constant liquid fertilization program using rates of 100- to 150-ppm nitrogen with every irrigation or apply 200- to 250-ppm nitrogen as needed. Growers frequently incorporate controlled-release fertilizers into the growing medium prior to planting at a rate equivalent to 11?4-11?2 lbs. of nitrogen per yard of growing mix.
Luna should be kept evenly moist and never allowed to wilt: Growing hibiscus too dry and allowing them to wilt could result in lower-leaf yellowing and flower bud abortion. When irrigation is necessary, I recommend growers water plants thoroughly and allow the growing medium to dry slightly between waterings.
The best quality is achieved when hibiscus are grown in full sun or greenhouses with no shading materials. High light intensities produce short plants and promote better branching and more flowers per plant. Hibiscus grown at low light levels tend to be lower quality as they become elongated, form less branches and flower less profusely than those produced at ambient light levels. To promote better branching, space the plants so there is good light penetration to the basal branches.
When producing Luna in containers, it is often necessary to control plant height. Providing adequate space between the plants is the best and most-effective method growers can practice to control plant height during production. Growers commonly spray multiple applications of a tank mixture of B-Nine (Chemtura Corp.) at 3,750 ppm and Cycocel (OHP) at 1,000 ppm or Sumagic (Valent USA) alone at 7.5 ppm over their hibiscus crops. It is best to begin PGR applications about one week following a pinch and apply them at 7-day intervals if additional control is necessary.
There are a number of insects and diseases that are often observed infesting hibiscus crops. Aphids, Japanese beetles, spider mites, thrips and whiteflies are often prevalent and only cause a minimum amount of injury to the crop. Of the diseases hibiscus contract, growers observe leaf spots caused most frequently by Alternaria and Cercospora. To control these diseases, it is best to manage the environment by providing proper plant spacing and adequate air movement, maintaining a relative humidity below 70 percent, and if desired, following a preventative spray program using appropriate chemicals. Growers should have routine scouting programs to determine the presence of these pests and if and when control strategies are necessary. Upon early detection, these insects and diseases can easily be controlled with the appropriate fungicides or insecticides.
Hibiscus are obligate long-day plants and will not flower unless they are grown under long-day conditions. Growers should produce them during times of the year when the photoperiods are naturally long or provide long-day photoperiods during production.
After long days are provided, the time to flower largely depends on growing temperatures. For optimum development, growers should provide 70-80º F days and 68-72º F nights. Production of hibiscus using lower temperatures results in an increase in the overall production time and causes foliage to appear chlorotic.
The amount of time to properly schedule the crop depends on the factors mentioned above — photoperiod and temperature — and is also influenced by pinching. When a 1-gal. crop is not pinched, plants can bloom in as little as eight weeks. If a pinch is conducted at the time of transplant, the time to finish increases to 10 weeks. A minimum of 14 weeks should be anticipated for larger sizes such as 2-gal. containers that may need two pinches to produce an aesthetic product.
Always look ahead at the desired sales date to determine if there is adequate time to pinch plants back and reach flowering on a specific date. It may not be necessary to pinch hibiscus that are being grown in small containers, as they will fill out the pot without pinching.
Pan American Seed Company brought the hibiscus Luna series to the market. Seed and plug flats are available exclusively through Ball Seed sales representatives.