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John Grimshaw & Tom Christian (2021)
Grimshaw, J. & Christian, T. (2021), 'Fagus' from the website Trees and Shrubs Online (treesandshrubsonline.
Ten to eleven species and one nothospecies of Fagus are found across the northern hemisphere (Govaerts et al. 2020; Huang et al. 1999). All are described here, except the Chinese F. chienii W.C.Cheng which we do not believe to be in cultivation, and to which the Flora of China does not afford treatment on account of its uncertain status (Huang et al. 1999).
The Beeches are deciduous trees with smooth bark and acute, elongated winter buds. The leaves are alternate, distichous and plicate in bud; the lamina is thin and the lateral veins are parallel, terminating with an acute or obscure marginal tooth. Stipules are prominent in young growth, but soon fall. Fagus is monoecious and the inflorescences are unisexual. Staminate inflorescences are produced in axils at the base of branchlets; they are capitate and contain numerous insignificant flowers. Pistillate inflorescences are short, stiff and axillary and bear two flowers. These are subtended by a single cupule, three- or four-valved; the cupule is dehiscent, with short, stout spines. The fruit is a nut and there are two per cupule; they are distinctly three-angled and may have a small wing (Nixon 1997; Huang et al. 1999).
There are few deciduous trees more noble than the European Beech Fagus sylvatica: it is no wonder that Elwes & Henry (1906) began their epic work with its account, and that this ran to 22 pages of text. It remains a mainstay of the grand landscape and an important woodland and ornamental tree across northern Europe, and is the benchmark against which to compare other species. Excellent new cultivars continue to be selected, adding to the many already known, and often incorporating several forms of variation in one tree. Other beeches are also handsome and useful trees, but seldom have all the same qualities, and few cultivars have been selected from them. In the hot and humid parts of East Coast North America, from about Washington DC southwards, F. sylvatica fails to thrive and is better replaced by the suckering native F. grandifolia, or perhaps by some of the East Asian species.
None of the east Asian species can be described as common in cultivation. Most of them are represented only by a scattering of specimens in botanical collections, and although some have been intermittently offered for sale by European and North American nurseries, they remain rare. The taxonomy of east Asian Fagus remains controversial: the Flora of China (Huang, Zhang & Bartholomew 1999) consider some populations in Hubei, Hunan, Shaanxi, Sichuan and Zhejiang referable to F. hayatae (treated here as a Taiwanese endemic), while the World Checklist of Fagaceae (Govaerts et al. 2020) refers only populations in Sichuan and Zhejiang to F. hayatae, presumably following authorities such as Lu & Pan (1998) in referring the others to a broad-concept F. lucida. Further research is clearly needed to resolve some of the underlying issues, and when met in collections an open-minded attitude to identification is recommended. The species from central and western China are often abundant in an important warm-temperate forest type, intermediate between the broadleaved-evergreen forest of lower altitudes and latitudes, and the conifer-dominated cool-temperate forests of higher ones. Few of the associated species, which include many evergreens, are fully hardy in our area except in the mildest localities (Hukusima et al. 2013).
All species of beech prefer light soils with good drainage, but their shallow rootplate makes them vulnerable to drought and windthrow. The very dry summers of 1976 and 2018 (pers. obs.) affected many F. sylvatica growing on thin soil above chalk in southern England. Both the European and American Beeches are considered to be at great risk from climate change in many parts of their natural ranges (Sternberg 2004; Hemery & Simblet 2014).
Fagus is best raised from seed, either sown when fresh in autumn or kept cool and dry until spring. Cultivars are reproduced by grafting, and to the horticulture student Fagus is a forgiving genus on which to hone this skill. Elwes & Henry (1906–1913) recommended delaying sowing seed until after frost, as seedlings are easily killed by freezing. Predation by animals is also a significant risk to both seed and seedlings. All beech fruit irregularly, having mast years in which large quantities of viable seed are produced, providing a feast for numerous birds and mammals and enabling mass regeneration, followed by several to many years in which almost no viable seed is produced. In Britain and Ireland, at least, the greatest threat to all Fagus species is the Grey Squirrel Sciurus carolinensis, which strips the bark, especially in the canopy, frequently girdling and killing branches or the main trunk, leading to poor shape and the risk of dead tops blowing out. This has led to commercial planting of F. sylvatica being deemed unviable by many foresters, unless squirrel control is exceptionally good (Hemery & Simblet 2014).
Beeches are generally unaffected by pathogens, but Beech Bark Disease is significant in both North America and Europe. It is the outcome of an insect-fungus complex, which results when the Beech Scale insect (Cryptococcus fagisuga) feeds on beech bark producing lesions that become infected by the fungus Neonectria faginata. It eventually kills trees as the stem becomes girdled by multiple bark lesions (Sternberg 2004, FOREST INVASIVES CANADA). A new disease of unknown cause is becoming a concern in the United States: Beech Leaf Disease was discovered in Fagus grandifolia in Ohio in 2012 and is spreading rapidly. Symptoms are dark patches between the veins, followed by leaf distortyion and necrotic lesions. It soon causes canopy-thinning and ultimately tree death (FOREST INVASIVES CANADA ). It is clear that great care needs to be taken to prevent this disease spreading. F. sylvatica has been known to be susceptible to several species of Phytopthora across its extensive range since at least 1938, and in more recent times has been affected by the infamous species P. ramorum and P. kernoviae. Symptoms of these and other Phytopthora species on Beech include root and collar rots, and bleeding aerial lesions (Brasier & Jung 2006).