A tree to c. 30 m, intermediate in features between its parents; trunk often straight. Bark variable and potentially resembling either parent’s: grey or rufous, variably papery or scaly. Shoots slender (1 - 2 mm thick), with few or no short hairs and few or many long hairs; leaves 4 - 8 cm long, dark green or slightly glaucous, never plane, narrowly ovate, with a cuneate or rounded base which is sometimes oblique; variably roughened with some downy papillae; finely toothed and more or less lobulate at least near the base; petiole c. 4 mm long. Cupule c. 15 - 18 mm long (smaller than that of N. glauca and larger than that of N. obliqua) (Donoso & Landrum 1979).
Distribution Chile Valparaíso, Metropolitano, O'Higgins, Maule, Ñuble and Bío Bío Regions, where the parent species' ranges overlap.
Habitat Coastal forests, growing alongside its parents.
USDA Hardiness Zone 8
RHS Hardiness Rating H4
Conservation status Not evaluated (NE)
Taxonomic note Both parent species are placed by Heenan and Smissen within the genus Lophozonia in their revision of Nothofagus (Heenan & Smissen 2013). N. × leonii was however omitted from their species list, presumably due to an oversight, so that the name required by their nomenclatural system for this taxon (i.e. Lophozonia × leonii) had still by 2020 to be validly published. The variant spelling ‘leoni’ is occasionally found online.
Nothofagus × leonii was one of several Andean Nothofagus first introduced to Europe by the Forestry Commission in 1976-9, but by 2020 the Commission no longer seemed to hold records to indicate the location or survival of any of these plantings. However, several examples passed on to specialist collections have thrived, suggesting that the hybrid may grow more rapidly and reliably across the UK and Ireland than its parent N. glauca seems likely to do. The largest is a magnificent tree in the Brentry area of the Sir Harold Hillier Gardens, received from the Forestry Commission in 1982 and 24 m × 52 cm dbh in 2017 (Tree Register 2020), which has a columnar trunk supporting a dense canopy, and the same collection also has two young trees grown from seed collected by Bernardo Escobar (Tree Register 2020). A specimen grown by Martin Gardner (pers. comm. 2020) and Sabina Knees in Edinburgh, from a wild collection made by Paulina Hechenleitner Vega in 2002 is now 12 m tall with a dbh of 20 cm. [In New Trees (Grimshaw & Bayton 2009) it was reported that a specimen collected by David Rae and Peter Baxter’s collection (no. 22) in Chile in 1996 at Benmore, was this hybrid, but it has been verified as being N. dombeyi (M. Gardner pers.comm. 2020).]
Some variability can be expected, and it is possible that some trees in cultivation are second-generation seedlings from wild-origin primary hybrids, and therefore may show grandparental characteristics in different proportions. Trees with the papery orange bark and the bluish foliage of Nothofagus glauca are likely to be considered the most attractive. The largest group of cultivated trees, planted in 1997 in the National Collection at Wakehurst Place in West Sussex, is quite uniform except in terms of the bark, which can sometimes resemble the hard greyish scales of N. obliqua. (Tree Register 2020).