From Greenhouse Product News
Propagated from seed, Fleuroselect’s Novelty Award winner makes gardens smolder with bright crimson, maroon and purple foliage and bold white coral bell–shaped blooms.
- By Paul Pilon
No perennial program is complete without several heuchera cultivars. Heuchera has become incredibly popular and widely grown, namely thanks to the characteristics of the foliage as well as its coral bell–shaped flowers borne on wiry stems. In recent years, the most notable cultivars introduced have been propagated from tissue culture and are typically moderately priced. Several years ago, Kieft Seeds introduced Heuchera ‘Melting Fire’, which provides a premium appearance and performance, but as a seed-propagated cultivar, it offers growers cost effectiveness many cultivars from tissue culture cannot provide. For commercial growers, ‘Melting Fire’ provides incredible uniformity and shelf appeal.
The new curly leaves of ‘Melting Fire’ emerge fiery red; at maturity, the foliage appears heavily ruffled with deep maroon coloration. With new and old leaves on each plant, there’s an interesting blend of red, maroon, and purple foliage throughout the growing season. The mounded, attractive clumps remain compact, measuring a tidy 8 to 12 inches across and 18 inches tall when in bloom. Wiry flower stems bearing numerous small white coral bell–shaped flowers appear in the late spring and continue throughout the early summer months. These attributes have earned ‘Melting Fire’ the Fleuroselect Novelty Award.
As with most heuchera cultivars, it performs best when grown under partial shade. ‘Melting Fire’ is both cold and heat hardy in USDA Hardiness Zones 4 to 9 and AHS Heat Zones 8 to 1. Heuchera are commonly used as accent plants, border plants or components in mixed containers. The blooms attract both butterflies and hummingbirds to the garden, but they can also be used as cut flowers. Heuchera are also resistant to deer.
The heuchera Melting series is propagated from seed. The seeds are small and may be difficult to handle; sow multiple seeds per cell. Do not cover the seed with germination mix or vermiculite after sowing or, if a covering is preferred, ensure only a very, very thin layer is applied on top of the plug flats. Moisten the seed flats and move them into a warm environment, where the temperatures can be maintained at 65-70° F for germination. Germinate heuchera in a chamber where uniform moisture levels and temperatures can be maintained. Keep the media moist but not saturated during this stage to avoid the risk to decreasing germination rates.
Seedlings will emerge 14 to 21 days after sowing. Following germination, reduce the moisture levels and allow the growing medium to dry out slightly before watering to help promote rooting. Fertilizers can be applied once the true leaves are present using a balanced water soluble source; applying 100-ppm nitrogen every third irrigation or 50 ppm with every irrigation. Plugs will be ready for transplanting in nine to 11 weeks when grown at 65° F.
Growers often have difficulty germinating heuchera during the summer months. For the best results, avoid starting them during this time of year unless you can provide cool conditions. Temperature-controlled germination chambers are ideal for summer propagation.
Heuchera ‘Melting Fire’ is most suitable for production in small container sizes; quart- to gallon-sized containers are most common. Most commercially available peat- or bark-based growing mixes work well, provided there is adequate drainage and the pH can be maintained between 5.8 and 6.2. When planting, take care to not bury the crown of the plant too deeply. After potting, the original soil line of the plug should be even with the surface of the growing medium of the new container; planting them too deeply will lead to crop variability and losses.
They can be grown using light to moderate fertility levels. Growers using water-soluble fertilizers either apply 100 to 150 ppm of nitrogen as needed or feed with a constant liquid fertilization program using rates of 50- to 75-ppm nitrogen with every irrigation. Controlled-release fertilizers can be applied as a topdress to the media surface using the medium labeled rate or incorporated into the growing mix prior to planting at a rate equivalent to 1.0 to 1.25 pounds of elemental nitrogen per yard of growing medium.
Heuchera does not tolerate overly wet or dry conditions and should be grown under average irrigation regimes. When the root zones are waterlogged, they become prone to crown and root rot pathogens, which can quickly lead to crop losses. Overly dry growing conditions may cause injury to the root systems, which also leads to root rot problems. To prevent crown and root rots, avoid extreme wet-dry cycles. Under high light intensities, marginal leaf burn may occur if the plants become water stressed. When irrigation is necessary, water thoroughly then allow the soil to dry slightly between waterings.
Given its compact growing habit, it is seldom necessary to control plant height. However, reducing the height of the flowering stems is often beneficial for growers who ship plants in bloom. Applications of 30-ppm paclobutrazol (Bonzi, Paczol or Piccolo) or 5-ppm uniconazole (Concise or Sumagic) are both somewhat effective at controlling the height of the flower stems. Apply growth regulators when the flower stems are just beginning to elongate above the foliage. Two applications, applied seven days apart, will provide an adequate reduction of the flowering stalk without altering the overall appearance of the plant.
Insects and Diseases
Heuchera can generally be grown free of insects. Aphids, mealybugs, slugs, spider mites, thrips and whiteflies may appear occasionally but usually do not cause significant injury to the crop. None of these insect pests require preventive control strategies. Growers should have routine scouting programs to detect insect pests early and determine whether control strategies are necessary.
When the proper environmental and cultural factors are provided, heuchera can generally be produced without the occurrence of plant pathogens. There are several pathogens including Alternaria, Botrytis, Cercospora, Colletotrichum, Pestalotia, Septoria, Ramularia and rust (Puccinia heucherae) that cause foliar leaf spots on coral bells. The other potentially serious foliar problem is the occurrence of the bacteria Xanthomonas, which takes the appearance of small, brown, angular to circular spots with yellow halos. Crown rots caused by the pathogen Rhizoctonia and root rots from the pathogens Pythium, Phytopthora and Thielaviopsis may also become problematic.
To control these diseases, manage the environment with providing proper plant spacing, adequate air movement, humidity control and good watering practices. If desired, follow a preventive spray program using the appropriate crop protection products.
‘Melting Fire’ is easy to produce as a foliage plant. When transplanting from 72-cell plugs, coral bells grown in gallon-sized pots at 65° F typically take six to eight weeks from planting to finish, or nine to 11 weeks during the winter months. Heuchera can be forced into bloom by following the guidelines discussed below.
Heuchera propagated from seed have a juvenility phase and must reach a particular size or maturity before they are capable of producing flowers. Therefore, it is recommended to grow ‘Melting Fire’ at natural day lengths for at least six weeks in the late summer to allow them to reach a mature size (bulking) before vernalizing them. Heuchera has an obligate cold requirement for flowering. Vernalize small containers of coral bells that have been bulked up and considered mature for at least nine weeks at temperatures less than 44° F. Following the cold treatment, they can be produced at natural photoperiods; they are day-neutral plants that will bloom under short or long days. The time to bloom after vernalization is a function of temperature: ‘Melting Fire’ will bloom in about eight weeks at 65° F. Large vernalized plugs can be planted in the early spring and will flower similarly to plants that have been overwintered in the final containers.
Source: Greenhouse Product News October 2009 Volume: 9 Number: 10
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