Malus ( or ) is a genus of about 32–57 species of small deciduous trees or shrubs in the family Rosaceae, including the domesticated orchard apple, crab apples, and wild apples.

The genus is native to the temperate zone of the Northern Hemisphere.

Description

Apple trees are typically tall 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 they 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, varying greatly according to subspecies and cultivar.

Many apples require cross-pollination between individuals by insects (typically bees, which freely visit the flowers for both nectar and pollen); these are called self-sterile, so self-pollination is impossible, making pollinating insects essential.

A number of cultivars are self-pollinating, such as "Granny Smith" and "Golden Delicious", but there are fewer self-pollinating varieties than cross-pollinating ones. Several Malus species, including domestic apples, hybridize freely.

The fruit is a globose pome, varying in size from in 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.

Subdivision

36 species and 4 hybrids are accepted.

Species

36 species and four natural hybrids are accepted:

  • Malus domestica – domestic or orchard apple
  • Malus doumeri – Taiwan crabapple
  • Malus florentina – Florentine crabapple, hawthorn-leaf crabapple
  • Malus fusca – Oregon or Pacific crabapple
  • Malus halliana – Hall crabapple
  • Malus honanensis
  • Malus hupehensis – tea crabapple
  • Malus indica
  • Malus ioensis – prairie crabapple
  • Malus jinxianensis
  • Malus kansuensis – Calva crabapple
  • Malus komarovii (
  • Malus leiocalyca
  • Malus longiunguis
  • Malus mandshurica
  • Malus muliensis
  • Malus niedzwetzkyana – Niedzwetzky's Apple
  • Malus ombrophila
  • Malus orientalis
  • Malus prattii – Pratt's crabapple
  • Malus prunifolia – plum-leaf crabapple, Chinese crabapple
  • Malus rockii – native to China and Bhutan
  • Malus sikkimensis – Sikkim crabapple
  • Malus spectabilis – Asiatic apple, Chinese crabapple
  • Malus spontanea - nokaidō
  • Malus sylvestris – European crabapple
  • Malus toringo (syns. Malus sargentii, Malus sieboldii) – Sargent crabapple, Toringo crabapple, or Siebold's crabapple
  • Malus toringoides – cut-leaf crabapple
  • Malus transitoria – cut-leaf crabapple
  • Malus trilobata – Lebanese wild apple, erect crabapple, or three-lobed apple tree
  • Malus turkmenorum (syn. Malus sieversii) – wild ancestor of cultivated species Malus domestica
  • Malus yunnanensis – Yunnan crabapple
  • Malus zhaojiaoensis

;Hybrids

  • Malus × floribunda – Japanese flowering crabapple
  • Malus × kaido (syn. Malus × micromalus) – midget crabapple
  • Malus × soulardii
  • Malus × zumi

Formerly placed here

  • Macromeles tschonoskii (as Malus tschonoskii ) – Chonosuki crabapple and pillar apple

Selected artificial hybrids

  • Malus × sublobata – yellow autumn crabapple (M. asiatica × M. toringo)

Fossil species

After For example, the rootstocks of Malus baccata varieties are used to give additional cold hardiness to the combined plants for orchards in cold northern areas.

They are also used as pollinizers in apples 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 is placed near the beehives as orchard pollenizers.

Because of the plentiful blossoms and small fruit, crabapples are popular for use in bonsai culture.

Cultivars

These cultivars have won the Royal Horticultural Society's Award of Garden Merit:

  • 'Adirondack'
  • 'Butterball'
  • 'Comtesse de Paris'
  • 'Evereste'
  • 'Jelly King'='Mattfru'
  • 'Laura'
  • Malus × robusta 'Red Sentinel'
  • 'Sun Rival'

Other varieties are dealt with under their species names.

Toxicity

The seeds contain cyanide compounds.

Uses

thumb|upright=1.2|Ripe apples ([[Malus domestica|M. domestica)]]

thumb|upright=1.2|Baskets of crab apples for sale in Connecticut in 1939

Crabapple fruit is not an important crop in most areas. The fruit is rarely eaten raw due to the sour taste resulting from high levels of malic acid. Some species have a woody texture. In some Southeast Asian cultures, they are valued as a sour condiment, sometimes eaten with salt and chilli or shrimp paste.

Some varieties of crabapple, such as the 'Chestnut' cultivar, are sweet.

Crabapples are an excellent source of pectin. Using sugar and spices such as ginger, nutmeg, cinnamon, and allspice, their juice can be made into ruby-coloured crab apple jelly with a full, spicy flavour. A small percentage of crabapples in cider makes a more interesting flavour.

Applewood gives off a pleasant scent when burned, and smoke from an applewood fire gives an excellent flavour to smoked foods. It is easier to cut when green; dry applewood is exceedingly difficult to carve by hand.

References

  • Germplasm Resources Information Network: Malus
  • Flora of China: Malus
  • Virginia Cooperative Extension - Disease resistant crabapples
  • The PRI disease resistant apple breeding program: a cooperative among Purdue University, Rutgers University, and the University of Illinois.