Malus


Malus 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 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 ; 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. The genus Malus is subdivided into eight sections. The oldest fossils of the genus date to the Eocene, which are leaves belonging to the species Malus collardii and Malus kingiensis from western North America and the Russian Far East, respectively.

Species

36 species and four natural hybrids are accepted:Malus angustifolia – southern crabappleMalus asiatica – Chinese pearleaf crabappleMalus baccata – Siberian crabappleMalus brevipes – shrub appleMalus coronaria – sweet crabappleMalus crescimannoi Malus daochengensis Malus delavayi Malus domestica – domestic or orchard appleMalus doumeri – Taiwan crabappleMalus florentina – Florentine crabapple, hawthorn-leaf crabappleMalus fusca – Oregon or Pacific crabappleMalus halliana – Hall crabappleMalus honanensis Malus hupehensis – tea crabappleMalus indica Malus ioensis – prairie crabappleMalus jinxianensis Malus kansuensis – Calva crabappleMalus komarovii – Sargent crabapple, Toringo crabapple, or Siebold's crabappleMalus toringoides – cut-leaf crabappleMalus transitoria – cut-leaf crabappleMalus trilobata – Lebanese wild apple, erect crabapple, or three-lobed apple treeMalus turkmenorum – wild ancestor of cultivated species Malus domesticaMalus yunnanensis – Yunnan crabappleMalus zhaojiaoensis
;HybridsMalus × floribunda – Japanese flowering crabappleMalus × kaido – midget crabappleMalus × soulardii

Formerly placed here

Macromeles tschonoskii – Chonosuki crabapple and pillar apple

Selected artificial hybrids

Malus × sublobata – yellow autumn crabapple

Fossil species

AfterMalus collardii Axelrod, North America, EoceneMalus kingiensis Budants, Kamchatka Peninsula, Russia, EoceneMalus florissantensis MacGinitie Green River Formation, North America EoceneMalus pseudocredneria MacGinitie Green River Formation, North America EoceneMalus idahoensis R.W.Br. North America, MioceneMalus parahupehensis J.Hsu and R.W.Chaney Shanwang, Shandong, China, MioceneMalus antiqua Doweld Romania, PlioceneMalus pseudoangustifolia E.W.Berry North America, Pleistocene

Cultivation

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.
Some crabapples are used as rootstocks for domestic apples to add beneficial characteristics. 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

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. 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.
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. It is a good wood for cooking fires because it burns hot and slow, without producing much flame. Applewood is used to make handles of hand saws; in the early 1900s, 2,000,000 board feet of applewood were used annually for this purpose.