When visiting the garden this year, you’ve no doubt noticed the gorgeous, intergeneric hybrid called ×Digiplexis ILLUMINATION® ‘Flame’ that we planted in pots flanking the front door of the Main House. The curious name will make sense just as soon as I explain its heritage, and wipe away any thought of ’70s disco dancers you may be entertaining at the moment.
Intergeneric hybrids are crosses between closely related genera. A well-known example in the orchid world is ×Laeliocattleya, which is a cross between a Laelia and a Cattleya. In the case of ×Digiplexis, it is a cross between a foxglove (Digitalis) and Isoplexis, which is a shrub-like, short-lived perennial (zone 9 – 11) from the Canary Islands and Madeira.
Isoplexis typically grows up to 4 feet tall and 3 feet wide. It has foot-long upright flower spikes that are densely covered with tubular flowers, each a blend of vermillion, rust, and gold. Its common name, cresta de gallo, alludes to the fact that it is reminiscent of a cockscomb. The plant was originally thought to have been pollinated by sunbirds, having since been replaced by Canary Island Chiffchaffs and other warblers.
Scientists have done research on this genus and found that while it is pollinated by birds, the pollination is infrequent. Isoplexis has an answer for this: the flowers stay open and ready for pollination for several months at a time. This tender perennial will be in bloom throughout the summer in your home garden (June to September or October).
Hybridize Isoplexis with foxgloves (×Digitalis) and you have a long-blooming annual that reaches about 3 feet tall. The long duration of the hybrid’s bloom isn’t due to low pollination frequency, as the hybrid is sterile and doesn’t waste its energy producing seeds.
The vermillion in the blooms is infused with violet from the marriage of the two genera, and the tubular flowers still resemble cockscombs or, if you have a good imagination, a laughing mouth. Combine Isoplexis with the hardier foxglove and you get a short-lived perennial that is hardy to zone 8. The foliage on the hybrid resembles that of the foxglove, and this showstopper is ideal for a container.