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Nothofagus is restricted to the southern hemisphere. Its 42 or so species are found in southern South America, southeast Australia (including Tasmania), New Zealand, New Caledonia, New Guinea (including New Britain) and parts of south-eastern Indonesia (Govaerts et al. 2020; Nothofagus (2007–2008); Heenan & Smissen 2013). The genus has been separated from Fagaceae into its own family, Nothofagaceae, but both are included in the order Fagales together with Betulaceae, Casuarinaceae, Juglandaceae, Myricaceae and Ticodendraceae (APG 2003). The southern beeches are deciduous or evergreen trees or shrubs. The leaves are distichous, though appear decussate in bud, and are often plicate prior to expansion. They are entire or toothed, thin or firm in texture and covered in resinous glands. The veins are usually conspicuous, and their number can be a significant taxonomic character. Stipules are often large and peltate and may be persistent or caducous. Nothofagus is monoecious and bears separate staminate and pistillate flowers; all species are wind-pollinated. The staminate flowers are axillary, solitary or in groups of three, and sessile or with a short peduncle. The pistillate flowers are borne above the staminate flowers and are solitary or in groups of three (rarely seven); they are also axillary, subtended by a cupule with two to four valves. The cupule has foliose or glandular appendages. The fruit is a nut and there are most often three in each cupule; the central nut has two wings while the two lateral nuts have three wings. (van Steenis 1953; Hewson 1989).
Nothofagus is one of the most important southern hemisphere genera of trees for temperate gardens; only Eucalyptus greatly surpasses it in terms of the numbers of species which can be found in the bigger (and milder) collections, while only a few further genera, such as Cordyline and Pittosporum, provide more familiar sights in the smaller gardens of the UK and Ireland. A few Nothofagus even grow fast and reliably enough to have been used by progressively-minded foresters, and in southern England at least can now be encountered across the wider countryside. This said, no Nothofagus is particularly hardy - 20°C of frost might represent an absolute limit for the tougher species - and most have a limited tolerance of hot dry summers, so that their use has been very largely confined to the northern Atlantic fringe of Europe. The north-western seaboard of the United States and British Columbia may become more widely suitable in a warming climate; New Zealand also offers near-perfect conditions for cultivating at least half the genus, but the presence here of five endemic species has naturally deterred most of those islands' gardeners from experimenting with the Andean or Australian taxa. Certainly Nothofagus in general seem much more fully represented in gardens in the UK and Ireland than anywhere else in the temperate world, though this observation may in part reflect the better degree of record-keeping in these two countries when it comes to the performance of exotic trees. Much recently introduced Chilean material in Britain and Ireland owes its existence to the efforts of Martin Gardner of the Royal Botanic Garden Edinburgh and his colleagues through their longstanding work in Chile; we are indebted to him for his comments on the TSO text of Chilean taxa. There are currently three British and Irish National Plant Collections of Nothofagus: at Wakehurst Place in Sussex, at Mount Usher in Co. Wicklow, and at Crarae in Argyll.
Very nearly half of Nothofagus - those in Section Brassospora (or the genus Trisyngyne in Heenan and Smissen's reclassification) - are tropical trees which are unlikely to succeed anywhere in Europe and hence lie outside the scope of this treatment. Nothofagus pullei Steenis from mountains in New Guinea has been attempted by Tom Hudson at Tregrehan in Cornwall, but is ‘very tender and dies if it is a cloudy day’ (Grimshaw & Bayton 2009). A few of the temperate species are adapted to niche habitats, such as very wet, exposed mountainsides, and can also be difficult to grow. This has proved particularly true of N. gunnii, endemic to Tasmania.
The genus as a whole is normally assumed to be calcifuge; nearly all species are confined in the wild to variably acidic soils. Some of the more generally robust kinds have made worthwhile trees in gardens in the UK and Ireland which are situated over limestone or rich alluvium, but none of them are likely to survive in agressively alkaline, chalky soils. The ability of some species to cope with extreme maritime exposure in the wild should not be confused with a tolerance of cold or dehydrating winds in cultivation, and all species seem to prefer a degree of woodland shelter; most also show a quite high tendency to shatter or blow down in severe storms. Nor does a preference for high rainfall and humidity mean that any are particularly adapted to waterlogged conditions: like mountain-loving conifers they all enjoy a free-draining though well-watered mineral soil. All Nothofagus seem rather sensitive to drought during the growing season, though in the climate of the early 21st century this scarcely limits which ones can be grown in water-retentive soils even in south-eastern parts of England. A few species, such as Nothofagus nitida from the coldest and wettest parts of the southern Andes, are liable to fail when high temperates increase water-stress in summer. Others in contrast, such as N. moorei, N. glauca or N. macrocarpa whose natural ranges approach the Tropic of Capricorn, clearly prefer at least moderate warmth through the growing season.
As members of an order which provides northern gardeners with such familiar tree groups as oaks, beeches, birches and alders, many Nothofagus look less obtrusively - or enticingly - exotic when planted in Atlantic Europe or the north-western United States than do most of their fellow-habitants of the southern hemisphere; this is particularly true of the deciduous Andean species such as N. alpina (N. procera) and N. obliqua, which flush and shed their leaves in synchrony with most northern broadleaves, but in common with remarkably few other denizens of the forests of the former Gondwanaland. This has helped encourage the use of these two species in particular as landscape or framework plantings in gardens in the UK and Ireland, where fast-growing and generally disease-resistant specimens are expected to blend into their backgrounds quite unobtrusively.
To propagate threatened Chilean species, Gardner et al. (Gardner et al. 2006) recommend cuttings made from the tips of basal suckers and placed in a mist unit, with or without bottom heat. Soaking the seed for 24 hours in a 250 ppm solution of gibberellic acid enhances germination (Gardner et al. 2006). Seed from arboretum-grown specimens, on the limited evidence so far, can be quite likely to give hybrid offspring. We are very grateful to Martin Gardner of the Royal Botanic Garden Edinburgh for his comments on the draft entries for the Chilean species described here,
The name Nothofagus means 'false beech' or 'resembling the beech'; but 'Notofagus', meaning 'southern beech', would have been more appropriate, and it has been suggested that Blume, who first published the name Nothofagus in 1851, added the 'h' in error (Bean 1976). More recently, DNA sequencing and microscopic analysis of key features such as the shape of pollen grains have shown the genus to comprise four evolutionarily distinct clades, which in this account are defined as the subgenera Brassospora, Fuscospora, Lophozonia and Nothofagus, after R.S. Hill and J. Read (Hill & Read 1991). The 20 or so tropical species form the subgenus Brassospora, while Nothofagus as a subgenus is confined to the southern Andes, but otherwise these divisions cut across the intuitive distinctions which human observers are likely to make between the large- and small-leaved species, and the evergreen and deciduous ones. Peter Heenan and Rob Smissen (Heenan & Smissen 2013) have proposed that Nothofagus should be split into four genera under these four names (but with the subgenus Brassospora appearing as genus Trisyngyne, a name first published by Baillon in 1874). This would appropriately reflect the degree of apparent evolutionary remoteness between these sections, but such a revision of a group which already includes several nomenclaturally unstable entities has yet to gain favour, let alone popularity, outside New Zealand.
A long-standing website devoted to Nothofagus (in French) is comprehensive and well illustrated, and remains the most recommendable monograph on the genus (Nothofagus 2007–2008). The Red List of Nothofagus (Baldwin, Barstow & Rivers 2018) provides an up-to-date assesment of the conservation status of the species and much useful information about the genus, including the tropical species that are usually forgotten by gardeners in temperate countries. It records that 11 species are threatened with extinction, and highlights the need for more of these to be preserved in ex situ collections. We adopt these conservation assessments here.
A number of naturally occurring hybrids have been described or surmised between taxa within Nothofagus which are generally interpreted as good species; at least two others have arisen in cultivation between species from different parts of the world. A checklist of these crosses, ordered by which parent comes first alphabetically, is:
Nothofagus alessandrii × fusca: found at Woodbank Gardens (the Tasmanian Arboretum), Eugenana, Tasmania, and described by Ken Gillanders in 2008 as N. × eugenananus. (Since Nothofagus is understood to be a feminine noun, the correct spelling of the name should be N. × eugenanana, an emendation first made by John Grimshaw in New Trees in 2009.) This hybrid, whose leaves can turn crimson as they drop in winter or spring, is now cultivated in Australia (Teese 2019), but does not yet seem to have been grown in the northern hemisphere.
N. alpina × obliqua: first noted in cultivation in England, but also assumed to occur within the wild populations; treated on this site under N. × dodecaphleps.
N. antarctica × dombeyi: assumed to occur naturally but not yet assessed for its possible presence among cultivated trees; mentioned on this site under N. antarctica.
N. antarctica × pumilio: assumed to occur naturally and also suspected to have arisen spontaneously in Denmark; mentioned on this site under N. antarctica.
N. cliffortioides × fusca: naturally occurring and also recorded as planted trees in Scotland; treated on this site under N. × blairii.
N. cliffortioides × solandri: naturally occurring as part of a cline; mentioned on this site under N. solandri.
N. cliffortioides × truncata: naturally occurring with the parents; mentioned on this site under N. × blairii. Genetic research (Smissen et al. 2014) has suggested that wild populations of N. cliffortioides, N. fusca, N. solandri and N. truncata in New Zealand can also show evidence of mixed ancestry in all other possible combinations.
N. fusca × solandri: naturally occurring with the parents in New Zealand as part of a complex hybrid swarm; mentioned on this site under N. × blairii: N. × dubia Kirk.
N. fusca × truncata: naturally occurring with the parents in New Zealand and recently introduced to Britain; mentioned on this site under N. truncata.
N. glauca × obliqua: naturally occurring and also planted in the UK; treated on this site under N. × leonii.
N. menziesii × obliqua: first noted at Weston Park, England, in 1975, and now moderately widespread in cultivation in the UK; treated on this site under N. menziesii × obliqua.
N. solandri × truncata: naturally occurring with the parents in New Zealand; mentioned on this site under N. × blairii: N. × apiculata Colenso.
Leaves untoothed, or with fewer than 8 small, irregular teeth
Leaves with more than 8 regular teeth, or serrated
Leaves usually less than 15 mm long, never toothed
Leaves usually more than 15 mm long
Leaf oval, plane
Leaf rather triangular, the tip curled up and the sides curled down
Leaf sometimes with a few small step-like teeth
Nothofagus × blairii
Leaf entire or with teeth only near the tip
Nothofagus × apiculata, N. × dubia (mentioned on this site under N. × blairii)
Leaf usually with 7 or more pairs of lateral veins and (much) more than 5 cm long
Leaf usually with fewer than 8 pairs of lateral veins (or veins very obscure) and (much) less than 6 cm long
Leaf-stalk 6 - 11 mm long
Leaf-stalk usually (much) less than 8 mm long
Leaf rather lanceolate, regularly serrate, evergreen
Leaf rather oblong, irregularly or doubly-toothed, deciduous or semi-evergreen
Leaves mostly shed in spring
Nothofagus × eugenanana (see introduction above)
Leaves fully deciduous, shed in autumn
Lateral veins in 7 - 11 pairs
Lateral veins in 10 - 14 pairs
Nothofagus × dodecaphleps
Lateral veins in 14 - 18 pairs
Leaf very glaucous beneath; bark peeling in rufous, papery flakes; fruit a cupule more than 15 mm long
Leaf somewhat glaucous beneath; mature bark either papery or scaly; cupule size intermediate
Nothofagus × leonii
Leaf pale green beneath; mature bark with hard scales; fruit a cupule less than 16 mm long.
Cupule with undivided scales
Cupule with fringed, moss-like scales
Leaves with 1 to 3 regular or large teeth for each lateral vein
Leaves finely serrated, or with doubly-toothed lobules
Teeth very sharply triangular
Teeth rounded or rather round-tipped
Leaves fully deciduous, teeth very regular and rounded
Leaves more or less evergreen
Leaves about 20 mm long; 1 tooth per lateral vein
Leaves about 40 mm long; 2 (- 3) teeth per lateral vein
Leaves about 30 mm long
Leaves about 12 mm long
Leaf rather orbicular, with domatia (hairy pits) under the leaf-base
Leaf rather triangular; domatia absent
Leaf less than 15 mm long
Leaf 12 - 60 mm long
Leaves fully deciduous, lobulate, 2 - 4 cm long
Leaves semi-evergreen, shed through winter, lobulate, 3 - 6 cm long
Nothofagus menziesii × obliqua
Leaves fully evergreen, glossy, serrated, never lobulate
Leaves oval, teeth slightly irregular, very finely round-tipped; male flowers carried singly
Leaves elongated-triangular, with very sharp, very irregular teeth; male flowers in 3s, with 8 - 13 stamens
Leaves narrowly rhomboidal, with sharp, slightly irregular teeth; male flowers in 3s, with 5 - 8 stamens