Evergreen or semi-evergreen tree to 20 m tall, intermediate between its parents E. glutinosa and E. lucida. Young shoots slightly grooved. Leaves occasionally simple, especially on flowering shoots, but usually trifoliate-compound with one large terminal leaflet and two much smaller laterals, borne opposite. Greyish-green beneath. Simple leaves and terminal leaflets to 6 cm long with a short petiole. Lateral leaflets smaller, to 3 cm long, more or less sessile. Margins of simple and compound leaves entire, shallowly wavy, sometimes shallowly toothed toward the apex, flowers borne singly or in pairs at branch apices, 2–3(– 4) cm across, petals pure white, widely obovate and overlapping. (Bausch 1938; Cullen et al. 2011).
USDA Hardiness Zone 8a-11
RHS Hardiness Rating H5
Hybrids between the deciduous Chilean E. glutinosa and the evergreen Australian E. lucida first arose in cultivation during the early 20th century (Bean 1981). John Rodgers, head gardener to Sir John Ross-of-Bladensburg at Rostrevor, County Down, Northern Ireland, spotted seedlings intermediate between the two parent species which were growing in close proximity (S. O’Brien pers. comm. 2018). It can safely be assumed that these and subsequent hybrid seedlings were removed and carefully tended before their inevitable distribution among Sir John’s friends, including to Lord Aberconway at Bodnant. It was Lord Aberconway who first exhibited this cross, under the name ‘Rostrevor’, at the RHS show at Vincent Square on 1st September 1936 where it receivd an Award of Merit (Bean 1981).
It stands to reason that this hybrid would have occurred in numerous gardens at different times, a result of both deliberate and spontaneous crosses, with the result that E. × intermedia is actually a far more variable entity than is generally appreciated. Furthermore, back crosses are known with both parents. Those plants that are back-crosses with E. lucida (see ‘Grayswood’ below) tend to be rather handsome, with leaves more glacuous beneath than in ‘true’ E. × intermedia, while back-crosses with E. glutinosa tend, unsurprisingly, to be semi-deciduous, which during the autumn and winter months seems to make them look rather sickly. An extraordinary degree of diversity is appreciable in an informal hedge of seed-raised E. × intermedia growing near the tennis courts at Glenstal Abbey in Ireland. These plants exhibit considerable variation in leaf size and shape, in flower size, and to some extent in the timing of flowering (pers. obs. 2019). It is apparent that for many years now commercial nurseries have sold multiple forms of E. × intermedia under the name ‘Rostrevor’, for commercially sourced plants also vary, yet the older trees of ‘Rostrevor’ are remarkably uniform (pers. obs.). Seamus O’Brien (pers. comm. 2018) reports that a dwarf form of E. × intermedia grows at Mount Usher, County Wicklow, Ireland, where it has reached a lofty height of 1.5 m in 40 years. It has never flowered, which is surely a testament to Irish patience.
This obscure cultivar was purportedly raised at the garden at Grayswood Hill, Surrey, England, where the original tree was 11 m tall in the late 1990s. Another at the Sir Harold Hillier Gardens had, by 2001, achieved nearly 6 m height in 21 years since planting. There is also a multi-stemmed tree of c. 7 m height at High Beeches garden in West Sussex, England, where the accession cards attest to this particular individual’s pedigree – it was a gift direct from Grayswood Hill in 1969. The High Beeches accession card also reveals that ‘Grayswood’, while undeniably similar to ‘Rostrevor’, is subtly different. The parentage is given as ‘(E. glutinosa × E. lucida) × E. lucida’, and this is backed up by a verification made by Christopher Brickell dated 1980 (pers. obs.).
In spite of this pedigree, it is not surprising that there is little in the gross morphology of ‘Grayswood’ to make an immediate and striking distinction from ‘Rostrevor’, except perhaps that the undersides of the leaves are somewhat more glacuous than in ‘Rostrevor’, and the occurrence of simple leaves is more frequent (pers. obs.). The same may be said of other, unnamed back-crosses with E. lucida. Sarah Bray (pers. comm. 2018) says that the High Beeches tree of ‘Grayswood’ ‘flowers magnificently’ each year, but even so it is likely to only be of interest to the most avid collectors of Eucryphia. In 2015, Plant Heritage listed it as ‘vulnerable in cultivation’ (Plant Heritage 2015) and it does not appear to be commercially available anywhere, nor in cultivation outside the south of England.
‘Rostrevor’ is the name for the original cross of E. lucida and E. glutinosa which was extensively propagated and distributed following its discovery and naming. Bean asserts that this is a ‘vigorous and fast-growing’ cultivar, and we may add to this that it is a most attractive plant, finer in foliage and somewhat smaller in flower than E. × nymansensis. (Bean 1981a). As discussed in the main E. × intermedia article above, however, further occurences of this cross, both spontaneous and deilberate, soon followed, and unfortunately the name ‘Rostrevor’ has probably been erroneously assigned to many of these later entities with the result that today plants labelled ‘Rostrevor’ can be very variable.
The genuine, original ‘Rostrevor’ quickly became established in the nursery trade first in the UK and Ireland, and then in North America by the end of the 1930s (Jacobson 1996). Generally the oldest trees are quite uniform, combining typically trifoliate-compound evergreen foliage with large, saucer-shaped flowers (pers. obs.). Its hardiness is generally considered to be on a par with E. × nymansensis and there are fine examples growing in relatively cold locations, for example an 11 m tree at Drummond Castle, Perthshire, and a 12 m tree at Keir House, Dunblane, both in Scotland. The milder west coast of Scotland in naturally home to larger examples, indeed the largest known grows at Glenarn, near Helensburgh on the Firth of Clyde and in 2012 was 20 m tall. There are many examples in excess of 10 m height throughout the UK and Ireland, concentrated in milder western regions and across the south of England (The Tree Register 2018).
It is reportedly grown on the west coast of North America, for example at Washington Park Arboretum (University of Washington Botanic Gardens 2018) and at Heronswood, Washington State, USA. Heronswood nursery supplied a plant to the JC Raulston Arboretum in North Carolina in 1996, but this is not recorded as having survived in 2018 (JC Raulston Arboretum 2018). It is cultivated in New Zealand, for example at the Eastwoodhill Arboretum (MacKay 1996) and probably in Australia, although there is very little information available from here. It is commercially available from numerous European nurseries, but as noted above it is not always the genuine article, though often still very attractive.