There are two types of inter-specific hybrids that occur in horticulture:
- Those that are natural hybrids where their cytology (chromosome numbers) is compatible but where in nature the parent species are separated geographically or by flowering period, but where cross-pollination can be carried out in cultivation, sometimes by saving pollen.
- Those that can be obtained only in the laboratory due to incompatible cytology.
Natural inter-specific hybrids
x atkinsii – purportedly C. coum x persicum
A legendary but unlikely cross dating from 1853. It is unlikely because the chromosome values are not compatible as C. coum is 2n=30 and C. persicum is 2n=48. The flowers were apparently like C. coum in shape, but larger. with very pale pink to white corolla lobes and a magenta nose.
x drydeniae – C. coum subsp. coum x alpinum
Two species that in nature are separated geographically. Both species have chromosome counts of 2n=30. The hybrid is hardy but is usually grown in a pot in a cold glasshouse.
x hildebrandii – C. africanum x hederifolium
An inter-specific hybrid that is controversial insofar as some growers believe that the purity of C. africanum may be contaminated by unplanned cross pollination and others who doubt the benefits. Both species can be diploid (2n=34) or tetraploid (2n=68). The hybrid is safest grown in a pot in a frost-free glasshouse.
x marxii – C. purpurascens x purpurascens subsp. immaculatum
This hybrid was named at a time when some botanists considered C. purpurascens subsp. immaculatum to be the separate species C. fatrense. Since both taxa are now subspecies of the same cyclamen species, this is an invalid hybrid.
x meiklei – C. creticum x repandum
A very attractive hybrid that combines the leaf patterns of C. creticum with the more elegant pink flowers of C. repandum. Both species are 2n=20, but C. creticum has a rare variant that is 2n=22. The hybrid is best grown in a pot in a frost-free glasshouse.
x saundersiae – C. balearicum x rhodium subsp. peloponnesiacum
Another attractive hybrid with aims similar to C. x meiklei. Both taxa are 2n=20. The hybrid is best grown in a pot in a frost-free glasshouse.
x schwarzii – C. libanoticum x pseudibericum
An attractive but controversial hybrid. It combines the flower shape of C. pseudibericum with the flower colour of C. libanoticum and some confused it with C. pseudibericum f. roseum. In fact this is where the controversy lies. There are growers who say that many of the very pale variants of forma roseum are actually the hybrid. It sometimes causes great consternation among the judges at shows. Both parents are 2n=30. The hybrid should be grown in a pot under frost-free glass.
x wellensiekii – C. libanoticum x cyprium
A well-tried and much-loved hybrid that can tend either more towards one parent or the other, and this can be seen most readily in the leaf patterns. Both parents are 2n=30. The hybrid should be grown in a pot under frost-free glass.
x whiteiae – C. maritimum x hederifolium
A deliberate cross that resulted in several plants with thick rather bright leaves and stubby flowers, which had the overall appearance of C. hederifolium. The cross is however unlikely due to incompatible cytology. Cyclamen maritimum is 2n=84 and C. hederifolium is 2n=34.
Laboratory inter-specific hybrids
These are hybrids of species that cannot be produced naturally due to incompatibility in either the cytology or the pollen. They are therefore made in the laboratory using embryo rescue and are then made fertile by doubling their chromosomes using colchicine.
Experiments carried out in the early to mid 1990s by Dr Hiroshi Ishizaka at the Saitama Horticultural Experiment Station in Japan, established a protocol that successfully made the following crosses:
C. persicum x hederifolium, C. persicum x repandum, C. persicum x libanoticum, C. persicum x purpurascens, C. persicum x graecum and C. persicum x rohlfsianum.
Using colchicine to double the chromosomes, fertile plants were obtained of:
C. persicum x hederifolium, C. persicum x purpurascens, C. persicum x graecum, C. persicum x rohlfsianum.
The cross of C. persicum x hederifolium was reported in detail by Dr Ishizaka in the Cyclamen Society Journal (Vol 19, Dec 1995) and was repeated by Sahin in the Netherlands around 2000, the progeny surviving a northern European winter in the garden and it was said to flower almost continuously.
The cross C. persicum x purpurascens was completed using two different C. persicum florists’ cultivars, ‘Strauss’(scarlet) and ‘Pure White’ (white). From these crosses, three initial cultivars were produced: ‘Uruwashi-no-kaori’ (pale pink flower with magenta nose), ‘Kaori-no-mai’ (deep pink flower with dark magenta nose) and ‘Kokou-no-kaori’ (mid pink flower with magenta nose). Other cultivars have been registered since. The cross was repeated in Germany by Dr Aloma Ewald at the Institute for Vegetable and Ornamental Plant Production in Erfurt, between 1997 and 2001. This gave rise to the hardy scented cultivar Cyclamen x perpuris ‘Odorella’ which was briefly available commercially in 2005, in two flower colours: lilac-pink and white.
Dr Ishizaka’s fertile cross of C. persicum x rohlfsianum has persisted and comes readily from seed. It produces attractive plants with pale or dark green or pewter patterned leaves with rose-pink to deep pink flowers with a magenta blotch at the base of each corolla lobe. The flowers have characteristics of both parents including the exerted stamens and style of C. rohlfsianum. Given its parentage, this hybrid is not hardy and should be grown in a pot in a frost-free glasshouse.