As a complex of variably hybrid origin, with M. sieversii and M. sylvestris its major progenitors, a thorough but useful description is hard to pin down. Bean (1981) identifies the following shared characters: young stems covered with woolly down; leaves dull green, elliptic-ovate, usually rounded at the base, densely woolly beneath, margins irregularly saw-toothed; pedicels, hypanthium, and outside of calyx woolly; fruits indented at the base and usually also at the apex; calyx persistent in fruit.
Habitat Naturalized almost wherever in the world it is grown, in woods, thickets, hedgerows, fencelines, roadsides, abandoned fields, riversides, and by shores.
USDA Hardiness Zone 3-9
RHS Hardiness Rating H6
Conservation status Not evaluated (NE)
Taxonomic note Miller intended Malus pumila (from the Latin pumilus – small) to denote the Paradise Apple, a weak, low-growing form of M. domestica used as a rootstock, which he took to be a distinct species (Bean 1981). Until very recently it has been widely used for all forms of orchard apple (otherwise known as M. domestica), and sometimes also for their primary wild progenitor (for example by Juniper & Mabberley 2006; Grimshaw & Bayton 2009). While M. pumila is the earlier name, M. domestica has been conserved (Qian et al. 2010, Applequist 2017).
A camp-follower of humanity, the Orchard Apple belongs here in all its forms – eaters, cookers, cider apples, all kinds of self-sown wildlings, even some ornamental crabs which were chance products of apple breeding programmes. This is a hugely significant plant in cultural, nutritional, and economic terms (Juniper & Mabberley 2019; Peil et al. 2011), but peripheral to our subject, ornamental and landscape trees. Some M. domestica can certainly be most attractive in flower, fruit, and form; a decrepit old apple tree draped in a vigorous clematis or rose can be highly picturesque; but few would plant one purely for ornament and this is no place for a detailed treatment of the cultivars. A familiar tree, its naming and studies of its origin have proved surprisingly troublesome.
The wild species allied to M. domestica, with their relatively large fruits and persistent calyces, are poorly differentiated and incompletely understood. This makes work on the origins of the Orchard Apple more difficult. Until recently many have suggested a hybrid origin, usually in an unspecific way. Tutin et al. (1968), from a European perspective, suggest that it is probably derived from M. sylvestris, M. dasyphylla, M. praecox and ‘some Asiatic species’. Bean (1981) mooted the same potential ancestors, but emphasized its close resemblance to M. sieversii. Conversely, Barrie Juniper and David Mabberley (Juniper & Mabberley 2006, Mabberley et al. 2001) argued that it represents domesticated forms of Central Asian M. sieversii and that ‘there is no evidence [from some early molecular studies] to support the view that hybridization with other Malus spp. took place during the westerly migration of the orchard apple’ (Mabberley et al. 2001); Juniper & Mabberley (2019) perpetuate this view with little change, however, more recent molecular studies have provided copious evidence of significant genetic inputs from other species, most importantly M. sylvestris (Cornille et al. 2014), and hybrid origin should now be accepted beyond reasonable doubt.
A balanced contemporary account of the origin of M. domestica certainly begins with wild M. sieversii in Central Asia, already with large fruits adapted for seed dispersal by large mammals (Spengler 2019), and very diverse in horticulturally significant ways (Juniper & Mabberley 2019). Its domestication has been quite unlike that of annual crops, where selection over countless seed generations has resulted in genetic bottlenecks and reduced genetic diversity; even today, planting an apple seed will result in a tree that may express any of a variety of characteristics (Spengler 2019). Initial domestication may have amounted to little more than the vegetative propagation of desirable wild clones through lifting of root suckers or grafting. These early cultivated apples were carried westward on the Silk Road, deliberately, accidentally or both (Juniper & Mabberley 2019). As their cultivated range increased they encountered other wild apples and hybridized with them on a rather large scale: M. sylvestris is particularly important (Cornille et al. 2012, 2014; Duan et al. 2017); some cultivars even have chloroplasts derived from M. sylvestris, suggesting that these were descended on the female line from M. sylvestris rather than M. sieversii (Nikiforova et al. 2013). M. orientalis seems also to have been involved in Iran (Cornille et al. 2014). M. sieversii appears to have hybridized independently with M. baccata as it moved east on the Silk Road, giving rise to East Asian cultivated apples, notably M. asiatica (Duan et al. 2017). However, M. baccata has made some recent input into M. domestica, in part through breeding for scab resistance. In short, Malus domestica is a genetically heterogeneous complex of variably hybrid origin, with much of the outward appearance of M. sieversii.
The name Malus domestica is predated by several others, most notably by M. pumila, a name which has often been used for the Orchard Apple but sometimes also for its wild relatives in Central Asia. Qian et al. (2010) summarize the complex nomenclatural issues clearly; the widely used name M. domestica has been conserved (Applequist 2017). Even this name is used in different ways; while we follow much of the horticultural and genetic literature in using it only for the Orchard Apple, some would lump M. sieversii and related wild taxa into it (Royal Botanic Gardens, Kew 2020).
Distinguishing M. domestica from its wild relatives – especially M. sieversii – is not always easy; given the prevalence of crop-to-wild gene flow into M. sylvestris, M. sieversii and M. orientalis (Cornille et al. 2014) it might not even be a meaningful question in some cases. The characters listed by Bean (1981) above generally hold good; and M. sylvestris is much less hairy overall.
Thousands of cultivars have been selected. Most are for fruit and so are they are beyond our scope: descriptive lists of cultivars range from recommendations (Dunn (2010) selects about 130 old and new varieties based on garden performance in the UK) to the encyclopaedic (Bussey 2016, Morgan & Richards 2002, from North American and British perspectives respectively). A few ornamental crabs have emerged from fruit breeding programmes; these are listed alongside other hybrid cultivars. A third group of cultivars has been selected as rootstocks (see Malus Rootstock Cultivars). Baker (1991) includes a trustworthy introduction to growing apples on a domestic scale. Peil et al. (2011) provide a route into the labyrinthine literature of apple breeding.