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Nothofagus is restricted to the southern hemisphere. Its 34 species are found in southern South America, southeast Australia and Tasmania, New Zealand, New Caledonia and New Guinea (including New Britain) (Govaerts & Frodin 1998). 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. 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, and are subtended by a cupule with two to four valves. The cupule has foliose or glandular appendages. The fruit is a nut and there are three in each cupule; the central nut has two wings while the two lateral nuts have three wings (van Steenis 1953, Hewson 1989).
A key to the species in cultivation in the British Isles is given by Clarke (1971), though this does not incorporate all the species described below, and Grant & Clement (2004) present a key to the deciduous species. There is also a website devoted to Nothofagus (in French) which is comprehensive, well illustrated and highly recommendable (Nothofagus 2007–2008).
After Eucalyptus, Nothofagus is the most important southern hemisphere genus of trees for temperate gardens, with some species such as the robust Chilean N. obliqua quickly forming handsome trees in a range of different conditions. Many others, however, are less successful. As in Eucalyptus, there are many species that are not fully hardy in northern Europe and thrive only in the mildest parts. Some have very narrow ecological requirements, that can make them apparently almost ungrowable. The New Guinean and New Caledonian species, which make up the largest part of the genus, are almost entirely unknown in cultivation and are probably extremely tender. Of these, Nothofagus pullei Steenis has been attempted by Tom Hudson (pers. comm. 2007), but he reports that it is ‘very tender and dies if it is a cloudy day’.
Good drainage, a mild but not too warm site, high humidity and shelter from strong winds all seem to be important factors for growing the less frequently seen species. All require acidic or neutral soil. These requirements do limit the area in which Notho fagus can be grown, and they are found only in gardens on the western fringes of Europe and North America; their relative frequency in British gardens is deceptive. There are good representatives in many British and Irish arboreta, and no less than three National Plant Collections of Nothofagus: at Wakehurst Place, Mount Usher and Crarae Garden, Argyll. To propagate endangered Chilean species, 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 is quite likely to give hybrid offspring. This is exemplified by the recently described N. ×eugenanana K. Gillanders, the progeny of N. alessandrii and N. fusca, which arose at the Tasmanian Arboretum at Eugenana, Tasmania (Gillanders 2008).
In recent years there has been an important change to the nomenclature of the well-known species called Raulí in Chile, which may bring some order to a state of confusion. Bean (1976b: B16) and Krüssmann (1985a: K327) both used the name N. procera (Poepp. & Endl.) Oerst., with N. nervosa (Phil.) Krasser as a synonym. Poeppig and Endlicher (1838) originally named two species, one from high-altitude areas (N. alpina), the other from lower altitudes (N. procera), but both of these are forms of Raulí. The name N. procera Poepp. & Endl. was illegitimate (it duplicates an earlier name) and was later changed to N. nervosa (Lennon et al. 1987). Van Steenis (1953) first suggested that N. alpina was a hybrid, and Lennon et al. (1987) identified the parents as N. nervosa and N. obliqua (Mirb.) Blume. However, after examination of type material, Grant & Clement (2004) have determined that the correct name for Raulí is Nothofagus alpina, with N. nervosa and N. procera as synonyms. Nothofagus alpina does form a hybrid with N. obliqua, and this has been named N. ×dodecaphleps (see below).
The northern beeches, of which Fagus sylvatica is the type, form a very homogeneous group of invariably deciduous trees with broad leaves; they are confined to the temperate latitudes of the northern hemisphere. The beeches of the southern hemisphere are mainly evergreen and are a larger, more varied group, with almost forty species (against ten in Fagus). Of these nine are natives of temperate S. America (Chile and bordering parts of Argentina); three occur in Tasmania and Australia; five in New Zealand. It has quite recently been discovered that southern beeches dominate in some of the remote mountain forests of New Guinea, and sixteen species were described from this region in 1952-3. There are also five species in New Caledonia, two of which were described by Baillon in 1874, but in a new genus – Trisyngyne – which he believed to belong to the Euphorbiaceae.
As remarked above, the southern beeches are mainly evergreen. But seven are deciduous, all of them from Chile and Argentina except the Tasmanian N. gunnii. It is interesting that these deciduous species resemble the northern beeches in having the leaves plicately folded in the bud, i.e., concertina-wise; in the evergreen species they are folded along the midrib. The leading characters of Nothofagus are: male flowers solitary or in pairs or threes, sessile or shortly stalked (in Fagus they are borne in globose, many-flowered, stalked inflorescences); female flowers usually three in each involucre (two in Fagus), normally each flower producing a nutlet, of which the two outer ones are three-winged or three-angled and the middle one flattened; styles short, not elongated as in Fagus. The valves of the involucre are essentially the same as in Fagus but are often obviously composed of several scales (lamellae) and the processes are more varied in form. Sometimes, too, they are much narrower than the nutlets and do not fully enclose them.
The name Nothofagus means 'false beech' or 'resembling the beech'; but Notofagus, meaning 'southern beech', would have been more appropriate, and it has even been suggested that Blume, who first published the name Nothofagus, inserted the letter 'h' inadvertently.
There is no monograph on the genus Nothofagus, but a valuable key, which includes the S. American and Australasian species, was published by C. G. G. J. Van Steenis as part of a study mainly devoted to the species recently discovered in New Guinea (Journ. Arn. Arb., Vol. 34 (1953), pp. 328-38).
All the southern beeches so far introduced are hardy or nearly so in the woodland gardens of mid-Sussex, with the exception of N. moorei, which thrives only in the mildest parts. The deciduous species now in cultivation should grow satisfactorily over most of the British Isles (though N. procera is tender in some forms). The hardiest evergreen species is N. betuloides. Unlike the common beech, the southern beeches are not suitable for calcareous soils. They are poor wind-resisters in this country, possibly because they grow too fast and make top-growth out of proportion to their root-system.