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There are seven species of Eucryphia, three in mainland Australia, two in Tasmania and two in Chile and Argentina (Forster & Hyland 1997). This classic Gondwanan distribution is indicitive of the evolutionary origins of the genus and of the family to which it belongs, the Cunoniaceae. Eucryphia form columnar trees or shrubs with glabrous or pubescent branchlets and sticky, resinous terminal buds. The leaves are evergreen (except in E. glutinosa which is always deciduous, and some hybrids of which E. glutinosa is a parent may be semi-evergreen), opposite and simple or pinnate. Stipules are always present, though they are caducous. The flowers are produced singly or, less often, in small clusters. They are hermaphrodite and 4-merous, with an open bowl of white petals. The calyx lobes are imbricate and united at their apices; they detach at floral maturity by abscising at the base, forming a four-lobed calyptra. The fruit is a woody capsule with distinctive persistent styles (Bausch 1938; Dress 1956; Wright 1983; Harden 2000a).
Eucryphia are justifiably popular in milder areas for their white flowers borne in late summer and, in all but one case, their evergreen foliage. The larger species are among the most attractive of flowering evergreen trees hardy in our area. Most have been well known for some time but two were discovered relatively recently in Queensland, Australia. Eucryphia wilkiei was first found in 1970 and has been introduced to the nursery trade (see description), but the 1994 discovery E. jinksii is not known to be in cultivation except in Australian botanical gardens and from a single plant kept in a conservatory in Northern Ireland (Paterson 2018). In its native range it is a tree to 25 m, with white, fragrant flowers 5 cm across.
The earliest recorded introduction to cultivation is that of E. lucida from Tasmania, which according to Hillier & Coombes (2002) was introduced to Britain in 1820 and like so many Antipodean exotics it was initially treated as a tender plant for the conservatory. The Chilean species E. cordifolia and E. glutinosa followed in 1851 and 1859 respectively and by the early 20th century these three species were well established in European horticulture and some of the early hybrids were arising in cultivation.
Both E. cordifolia and E. lucida received RHS Awards of Garden Merit in 1936, following the introduction to Britain of two further species in 1915 (E. moorei) and 1929 (E. milliganii). There is a record of the two Chilean species being introduced directly to the USA in early 1920 (USDA 1923) though it is not known whether this introduction properly established either species in north American cultivation. Jacobson (1996) suggests E. glutinosa, E. × intermedia ‘Rostrevor’, and E. × nymansensis ‘Nymansay’ were all imported into North America, presumably from Europe, in c. 1937 and commercialised there shortly afterward.
All the various species performed well in the mild oceanic gardens of the western seaboard of Europe following their introductions, but perhaps nowhere more so than in the gardens of Cornwall and Devon and across the island of Ireland: a useful description of Eucryphia growing in gardens in Northern Ireland, seen on an IDS Study Period in 2017 is given by Paterson (2018). Sheltered inland gardens also proved suitable, such as at Nymans in Sussex, which was to become inextricably associated with the genus, and there is a record of E. lucida thriving on Isola Madre in Lake Maggiore, Italy in 1936 (Cocker 1936). E. glutinosa is the hardiest species and thrives even in gardens with cold, harsh winters, and was well established in collections throughout Western Europe by the 1930s.
This hardiness was to prove invaluable in expanding the cultivated range of the genus when E. glutinosa was a parent to two hybrids – E. × nymansensis raised c. 1915, and E. × intermedia raised before 1936. The various selections of these crosses, but especially their respective cultivars ‘Nymansay’ and ‘Rostrevor’ proved extremely adaptable and helped to popularise the genus through the rest of the 20th century.
The first years of the 21st century, though, have seen an undeniable boom in the genus’s popularity at least within the UK and Ireland, as species and cultivars are profiled in the popular gardening press and advocated for their usefulness in small gardens, especially as the severity of our winters diminish, and they are an increasingly common sight in suburban gardens. This has no doubt been helped by the relatively recent introduction of two beautiful pink-flowered forms of E. lucida. Their profile is also improving in other areas where they will thrive – western parts of Europe where the winters are not so severe, appropriate climatic zones in North America, especially the western seaboard, New Zealand, and increasingly in Australia as the greater use of natives is advocated.
In cultivation, they require moist but free drained, acid soil, although E. cordifolia and to a greater extent E. × nymansensis are tolerant of chalk soils. They all perform best when the upper part of the plant is in full sun for at least part of the day, but equally they need their roots to be shaded and cool in order to really thrive, and so benefit from appropriate companion planting to achieve this. Strong, cold winds can cause sometimes severe leaf scorching, so shelter from the worst winter winds is advisable, most especially for the Australian species and those hybrids lacking the hardier genes of E. glutinosa. Propagation by seed is straightforward, but Eucryphia have a track-record of hybridising freely in cultivation. Layering, and striking semi-ripe cuttings placed over a gentle bottom heat, are also reliable means of propagation.
The hybrids that have arisen in cultivation, and the selections of various cultivars from these, have caused some confusion over the years as to the correct lineage of the various named forms. In addition to the seven recognised species, E. cordifolia, E. glutinosa, E. jinksii (not discussed here), E. lucida, E. milliganii, E. moorei, and E. wilkei, the following hybrids are known to occur:
E. × hilleri (lucida × moorei) usually seen growing as cv. ‘Winton’;
E. × hybrida (lucida × milliganii) this hybrid occurs naturally in the wild in Tasmania;
E. × intermedia (glutinosa × lucida) usually seen growing as cv. ‘Rostrevor’;
E. ‘Madron’ exhibited in 1954, of uncertain parentage, not discussed here;
E. ‘Penwith’ (cordifolia × lucida), mistakenly assumed for some time to belong to E. x hilleri;
E. × nymansensis (cordifolia × glutinosa) probably the most widely cultivated entity within the genus.