Malus


Malus is a genus of about 30–55 species of small deciduous trees or shrubs in the family Rosaceae, including the domesticated orchard apple – also known as the eating apple, cooking apple, or culinary apple. The other species are commonly known as crabapples, crab apples, crabtrees, or wild apples.
The genus is native to the temperate zone of the Northern Hemisphere.

Description

Apple trees are typically talI at maturity, with a dense, twiggy crown. The leaves are long, alternate, simple, with a serrated margin. The flowers are borne in corymbs, and have five petals, which may be white, pink or red, and are perfect, with usually red stamens that produce copious pollen, and a half-inferior ovary; flowering occurs in the spring after 50–80 growing degree days.
Many apples require cross-pollination between individuals by insects ; these are called self-sterile, and therefore self-pollination is impossible, making pollinating insects essential.
There are a number of cultivars which are self-pollinating, such as Granny Smith and Golden Delicious. There are considerably fewer of these, compared to their cross-pollination dependent counterparts.
Several Malus species, including domestic apples, hybridize freely. They are used as food plants by the larvae of a large number of Lepidoptera species; see list of Lepidoptera that feed on Malus.
The fruit is a globose pome, varying in size from diameter in most of the wild species, to in M. sylvestris sieversii, in M. domestica, and even larger in certain cultivated orchard apples. The centre of the fruit contains five carpels arranged star-like, each containing one or two seeds.

Subdivisions and species

There are about 42 to 55 species and natural hybrids with about 25 from China, of which 15 are endemic. The genus Malus is subdivided into eight sections.
SubgenusImageScientific nameCommon nameDistribution
Section Chloromeles Rehd.Malus angustifolia Michx.southern crabappleEastern and south-central United States from Florida west to eastern Texas and north to New Jersey, Pennsylvania, Illinois and Missouri
Section Chloromeles Rehd.Malus coronaria Mill.sweet crabappleGreat Lakes Region and in the Ohio Valley, United States
Section Chloromeles Rehd.Malus ioensis Brittonprairie crabappleupper Mississippi Valley,United States
Section Chloromeles Rehd.Malus brevipes Rehdershrub apple
Section Docyniopsis Schneid.Malus doumeri A.Chev. Taiwan crabappleChina, Taiwan, Laos, Vietnam
Section Docyniopsis Schneid.Malus leiocalyca S. Z. HuangChina
Section Docyniopsis Schneid.Malus tschonoskii C.K.Schneid.Chonosuki crabapple and pillar appleJapan.
Section Eriolobus SchneidMalus trilobata C.K.Schneid.Lebanese wild apple, erect crabapple, or three-lobed apple treeAsia includes West and South Anatolia, Syria, Lebanon and North Israel, Europe from east section of Greek Thrace and southeastern Bulgaria
Section Florentinae M.H.Cheng ex G.Z.QianMalus florentina C.K.Schneid.Florentine crabapple, hawthorn-leaf crabappleBalkan Peninsula and Italy
Section Gymnomeles KoehneMalus baccata Borkh. 1803Siberian crabappleRussia, Mongolia, China, Korea, Bhutan, India and Nepal
Section Gymnomeles KoehneMalus halliana Koehne 1890Hall crabappleJapan and China
Section Gymnomeles KoehneMalus hupehensis Rehder 1933tea crabappleChina
Section Gymnomeles KoehneMalus mandshurica Kom. ex SkvortsovManchurian crabappleChina, Japan, eastern Russia
Section Gymnomeles Koehne MakinoJapan
Section Malus LangenfeldsMalus asiatica NakaiChinese pearleaf crabappleChina and Korea.
Section Malus LangenfeldsMalus chitralensis Vassilcz.Chitral Crab AppleIndia, Pakistan
Section Malus LangenfeldsMalus crescimannoi Raimondonorth-eastern Sicily
Section Malus LangenfeldsMalus floribunda Siebold ex Van HoutteJapanese flowering crabappleJapan and East Asia
Section Malus LangenfeldsMalus muliensis T.C.KuChina
Section Malus LangenfeldsMalus orientalis Uglitzk.Armenia, Georgia, Turkey, and Russia
Section Malus LangenfeldsMalus prunifolia Borkh.plum-leaf crabapple, Chinese crabappleChina
Section Malus LangenfeldsMalus domestica Miller, 1768orchard apple, includes Malus niedzwetzkyana and M. pumilaCentral Asia
Section Malus LangenfeldsMalus sieversii M.Roem.Central Asia in southern Kazakhstan
Section Malus LangenfeldsMalus spectabilis Borkh.Asiatic apple, Chinese crabappleChina
Section Malus LangenfeldsMalus sylvestris Mill.European crabappleEurope
Section Malus LangenfeldsMalus zhaojiaoensis N.G.JiangZhaojiao crab appleChina
Section Sorbomalus ZabelMalus fusca C.K.Schneid.Oregon or Pacific crabapplewestern North America from Alaska, through British Columbia, to northwestern California.
Section Sorbomalus ZabelMalus kansuensis C. K. SchneiderCalva crabappleChina
Section Sorbomalus ZabelMalus komarovii RehderChina, Manchuria, and North Korea.
Section Sorbomalus ZabelMalus sargentii Rehder.Sargent crabappleJapan
Section Sorbomalus ZabelMalus toringo de Vriese Toringo crabapple or Siebold's crabappleeastern temperate Asia, in China, Japan, and Korea
Section Sorbomalus ZabelMalus toringoides Hughescut-leaf crabappleChina
Section Sorbomalus ZabelMalus transitoria C.K.Schneid.cut-leaf crabappleChina
Section Sorbomalus ZabelMalus zumi RehderJapan
Section Yunnanenses G.Z.QianMalus honanensis Rehder.Honan CrabappleChina
Section Yunnanenses G.Z.QianMalus ombrophila Handel-MazzettiChina
Section Yunnanenses G.Z.QianMalus prattii C.K.Schneid.Pratt's crabappleChina
Section Yunnanenses G.Z.QianMalus yunnanensis'' C.K.Schneid.Yunnan crabappleChina

Natural Hybrids

For the Malus pumila cultivars, the culinary, and eating apples, see Apple.
Crabapples are popular as compact ornamental trees, providing blossom in Spring and colourful fruit in Autumn. The fruits often persist throughout Winter. Numerous hybrid cultivars have been selected. The following have won the Royal Horticultural Society’s Award of Garden Merit:-
Other varieties are dealt with under their species names.
Some crabapples are used as rootstocks for domestic apples to add beneficial characteristics. For example, varieties of baccata, also called Siberian crab, rootstock is used to give additional cold hardiness to the combined plant for orchards in cold northern areas.
They are also used as pollinizers in apple orchards. Varieties of crabapple are selected to bloom contemporaneously with the apple variety in an orchard planting, and the crabs are planted every sixth or seventh tree, or limbs of a crab tree are grafted onto some of the apple trees. In emergencies, a bucket or drum bouquet of crabapple flowering branches are placed near the beehives as orchard pollenizers. See also Fruit tree pollination.
Because of the plentiful blossoms and small fruit, crabapples are popular for use in bonsai culture.

Uses

Crabapple fruit is not an important crop in most areas, being extremely sour due to malic acid, and in some species woody, and for this reason is rarely eaten raw. In some southeast Asian cultures they are valued as a sour condiment, sometimes eaten with salt and chili pepper, or shrimp paste.
Some crabapple varieties are an exception to the reputation of being sour, and can be very sweet, such as the 'Chestnut' cultivar.
Crabapples are an excellent source of pectin, and their juice can be made into a ruby-coloured preserve with a full, spicy flavour. A small percentage of crabapples in cider makes a more interesting flavour. As Old English Wergulu, the crab apple is one of the nine plants invoked in the pagan Anglo-Saxon Nine Herbs Charm, recorded in the 10th century.
Apple wood gives off a pleasant scent when burned, and smoke from an apple wood fire gives an excellent flavour to smoked foods. It is easier to cut when green; dry apple wood is exceedingly difficult to carve by hand. It is a good wood for cooking fires because it burns hot and slow, without producing much flame.
Crab apple has been listed as one of the 38 plants whose flowers are used to prepare the Bach flower remedies.

Cultivars