Crop Culture Report: Digiplexis 'Illumination Flame'

December 16, 2013 - 12:22

Check out the stunning intergeneric foxglove hybrid that everyone is talking about.

With hundreds of new varieties being introduced to the marketplace every year at California Spring Trials, trade shows and the like, it’s easy to become jaded about new plants in general. But every now and then, a new plant hits the market that immediately catches everyone’s attention. Such is the case with digiplexis ‘Illumination Flame’, a new intergeneric foxglove.

Bred by Charles Valin at the UK breeding company Thompson & Morgan, ‘Illumination Flame’ resulted from a cross between the common foxglove and isoplexis, a Mediterranean shrub with unusual orange flowers. The resulting hybrid is truly intermediate in habit, with bushy basal branching, eventually forming a woody trunk and spikes of elegant, rosy-orange flowers. The real breakthrough, however, is the fact that this variety will not just flower for a few weeks, as most foxgloves would; ‘Illumination Flame’ flowers non-stop from late spring through hard frost in the autumn.

Propagation

‘Illumination Flame’ is most efficiently propagated from tissue culture, resulting in a very uniform, healthy and fully vegetative liner. There are currently a limited number of propagation nurseries licensed to wean the tissue culture plantlets and sell the hardened liners to growers. These offer both non-vernalized and vernalized liners. Check with your supplier to know what you will be receiving.

Planting and Bulking

The best crop quality comes from the planting of non-vernalized liners in autumn or winter, using a well-drained perennial mix with moderate fertility and a pH of 5.5 to 6.0. Larger pot sizes are recommended — the plant is too vigorous for pots smaller than 1 gallon. Larger color bowls or 2-gallon containers have produced premium crops with a strong retail appeal. During the bulking phase, it is important to maintain night temperatures above 65° F for the first few weeks. Lowering the temperature below 60° F for any length of time may result in premature budding.

Vernalized liners can be planted any time from February to April with one liner per gallon or 2-gallon container. Growing at lower temperatures (45 to 60° F, or outdoors in frost-free climates), since this produces a better finished quality.

Pinching

In contrast to standard foxglove, which produce a single terminal spike from a flat basal rosette, ‘Illumination Flame’ benefits from a single pinch, which promotes bushiness and the development of several flower spikes simultaneously. Remove the growing tip two weeks after planting if you receive unpinched liners. Keep the plants at night and day temperatures between 65° and 75° F for three to four weeks after pinching, until the lateral shoots are well developed.

Chill Period: the key to strong and early flowering

If you are starting with non-vernalized liners in autumn or winter, you will need to subject the crop to a chill period to induce flower initiation. ‘Illumination Flame’ requires a moderate chill in order to set flower buds, but without a chill period, the plants will generally not flower at all. Hence, once the plants have bulked sufficiently (i.e. when the lateral shoots are 2 to 3 inches long), chill the plants for at least four to six weeks at temperatures of 38 to  45° F. Longer chill periods are possible and can aid in the staging of flowering as well as maintaining plant quality.

Finishing: producing a high-value plant

After the chill period, the plants should be grown at high light levels (no shade) and moderately warm temperatures between 45 and 60°F. The finished product quality can be compromised by the soft growth that warmer temperatures promote thus avoiding overly warm greenhouse conditions will improve crop quality. Generally six to eight weeks are needed to finish after the chill period is complete, depending on pot size, temperatures and light levels. No PGRs have been applied with this crop to date, since the finished quality is very good if the plants are grown cool at high light levels. Constant liquid feed with a well-balanced fertilizer at 250- to 300-ppm nitrogen is recommended during the finishing phase.

Consumer Care Tips
‘Illumination Flame’ can be a stunning specimen plant for larger containers or when used in mass plantings. Flowering non-stop from May to hard frost, it grows best in full sun but tolerates partial shade locations as well. New flower spikes are produced in the leaf axils, guaranteeing a continuous display all summer long. Since the plants are self-cleaning and sterile, the individual spikes continue to grow and flower, often flopping over as they age, but these can easily be removed allowing the lateral spikes to develop their full potential and to keep the plants neat and tidy. ‘Illumination Flame’ has proven to be a bee and hummingbird magnet and is otherwise care-free. Watch for spider mite damage during hot, dry spells or after stress. Care should be taken to ensure that the plants are watered and fertilized regularly; ‘Illumination Flame’ can be a thirsty plant during hot and sunny weather. As for winter hardiness, ‘Illumination Flame’ tolerates light frosts without problems, but has shown to be Zone 8 hardy.

For additional product information, visit www.digiplexis.com or go to www.facebook.com/DigiplexisIllumination.

Availability

The following young plant companies will be offering digiplexis ‘Illumination Flame’ this coming season: James Greenhouses, Pacific Plug & Liner, Peace Tree Farm, Plug Connection and Skagit Gardens.

About The Author

Garry Grueber is managing partner of Cultivaris North America LLC. He can be reached at garry@cultivaris.com.

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