Populations of hybrid seedlings are likely to be particularly variable, and such populations will need to be grown in the field in order to assess their potential as ornamentals. Candidate seedlings will also need to be propagated as rooted cuttings, to allow variety trialling
The ability to root cuttings from selected individuals is important, because otherwise it will be difficult to produce plants commercially, and impossible to register the new varieties. Prima Bio's breeding and selection therefore places considerable emphasis on selecting some parents for good rooting ability, in addition to ornamental attributes and cold hardiness. From work in eucalyptus species and selections important in forestry, it is known that certain ones will root very readily and confer this ability to hybrid progenies, while others cannot be rooted at all. But rooting of less vigorous ornamental species has hardly been studied. Therefore, an important part of Prima Bio's programme is to examine rooting of candidate parental species, and to use individuals identified as having good rooting as parents. See Rooting of selections for more details.
Prima Bio's first hybrids were made in 2004. The mother trees were some E.gunnii trees selected for particularly attractive bark and foliage, and some E.pulverulenta 'Baby Blue'. The latter is a dwarf variety of a shrubby species grown commercially for its striking cut foliage, though its growth habit is untidy. Pollen for other crosses has come from a wider variety of species and locations, and includes some of the spectacular red-flowered species. Many other sources of pollen have been collected and are stored for future use.
An outdoor breeding arboretum was established in North Kent in 2004. Further shrubby species have been established in a protected polytunnel at East Malling Research station. This location is used for mainly for tender species, including some from Western Australia, that are unlikely to survive cold wet winters outdoors. It is also used for species that flower in winter in the UK, to facilitiate hybridisation.
Some of the species planted have been bought as containerised stock from nurseries in the UK. However, many of the species are not available commercially in the UK, or are not available from seed provenances of greatest interest. These species have been grown by Prima Bio from seed, or were raised in nurseries in Spain and Portugal in winter and imported as young seedlings. The experience of growing and over-wintering seedlings of diverse species has been invaluable as a means of learning about likely cultural requirements of different hybrid types. Certain species have been exceptionally free of pests and diseases. Many supposedly tender species were apparently undamaged by the 2004/05 winter despite their foliage being white with frost and their pots at least partly frozen on many mornings. Some have also been covered with snow on several mornings! Temperature loggers have been installed to allow cold tolerances to be quantified.
Prima Bio intends to work with other companies to bring its varieties with significant commercial potential through the evaluation and registration phases, and obtain royalties. Companies interested in such partnerships are welcome to discuss possibilities, at any stage.
One of the Eucalyptus caesia ssp magna that has flowered prolifically in the polytunnel used for breeding at East Malling. The polytunnel is frost-free in winter, and solar gain keeps it approximately 5° above ambient daytime temperatures in summer. Many eucalypts from Western Australia grow well and have initiated flower buds in the tunnel, but E. caesia has been the most easily-grown and free-flowering species.