August 2002

Heuchera ‘Fireworks’ Coral Bells By Paul Pilon

The Native American perennial heuchera has become one of the hottest, most must-have perennial plants for today’s gardens. Heucheras belong to the family Saxifragaceae, which includes many other popular perennials such as astilbe, berginia, heucherella, rodgersia, saxifraga and tiarella, to name a few. In recent years there has been an explosion of breeding conducted to improve flower color and provide better foliage characteristics.

Heuchera “Fireworks”, which has come out of Terra Nova Nurseries, Tigard, Ore., is a result of such breeding work. Fireworks is best recognized by its “explosive” display of light, coral-bell-shaped flowers on wiry stems held over the lightly ruffled bronze foliage. It is a prolific and long-lasting bloomer that continues flowering from May-August and attracts both butterflies and hummingbirds. It has good re-blooming characteristics and can be used as a cut flower.

Fireworks is suitable for production in Zones 4-9. It grows best in full sun to partial shade. When grown under shady conditions, it still blooms well, and the foliage will become veiled (a light silver coloration between the veins). As with most heucheras, it thrives in rich, moist, well-drained soils.

Propagation

Like many of the new varieties of heucheras, Fireworks is vegetatively produced by means of tissue culture. Tissue culture has allowed this and many other new varieties to reach the market in a relatively short period of time. This is a patented variety and is available as plugs from licensed producers throughout the country.

Production

Heucheras perform best in a well-drained media with a pH between 5.8 and 6.2. They are light to moderate feeders requiring nitrate levels of 50-100 ppm under a constant liquid fertilizer program, or a controlled-release fertilizer at a rate equivalent to one pound of nitrogen incorporated per yard of growing medium. Heucheras require an average amount of irrigation as they do not tolerate really wet or overly dry conditions. Under high light intensities, marginal leaf burn may occur if the plants become water-stressed. When transplanting from a 72-cell plug, Fireworks grown at 65¡ F typically takes eight weeks to finish in a 1-gallon pot in the summer and 11 weeks during the winter months.

Fireworks, like most heucheras, do not have many pests. Occasionally aphids, whitefly, mealybugs, snails, Japanese beetles or foliar nematodes may appear, causing only a minimal amount of crop injury. In outdoor production sites or landscape situations, the black vine weevil or the strawberry root weevil could infest and cause significant damage to the stems and crowns.

The primary disease to watch for is Rhizoctonia crown rot. Fireworks is most susceptible to Rhizoctonia when grown under cool conditions, such as going into or coming out of winter dormancy. Botrytis is another disease that could become problematic. Botrytis, like Rhizoctonia, often occurs around the over-wintering process but is also likely to occur under dense plant canopies. Other observed diseases include Pythium, Phytopthora, powdery mildew, rust and leaf spots. Pseudomonas and Xanthomonas have been observed on some heuchera varieties but are not a major concern at this time. Pseudomonas will appear as reddish-brown spots that may cause the leaf to distort, and Xanthomonas takes the appearance of small, brown, angular to circular spots with yellow halos. With good watering practices and adequate air circulation, the occurrence of most diseases can almost be negated.

Height control is seldom necessary to control the growth of the leaves; however, reducing the height of the flowering stems or panicles is often beneficial for growers who ship plants in bloom. Apply Sumagic at five ppm (this is a northern rate, adjust your rates accordingly) when the panicles begin 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. When grown under high plant densities, plant height can be controlled by applying Sumagic at five ppm to the foliage as the plant canopy begins to enclose.

Forcing

Research has shown that cultivars of heucheras must reach a particular size or maturity before they are capable of producing flowers. Therefore, it is recommended to grow Fireworks at natural daylengths for a minimum of 10 weeks to allow them to reach a mature size before placing them through the cooling period. To achieve complete flowering, the required cold period is a minimum of 12 weeks at 41¡F or below. After the cold requirement is achieved, produce Fireworks at any daylength, as they are day-neutral plants. At an average temperature of 68¡ F, they will reach full bloom in approximately 5-7 weeks. Producing at a cooler temperature will increase the time to flower but will improve the overall quality.