Malus is a genus of about 30–55 species of small deciduous apple trees or shrubs
in the family Rosaceae, including the domesticated orchard apple. The other
species are generally known as crabapples, crab apples, crabs, or wild
apples. The genus is native to the temperate
zone of the Northern Hemisphere. Description
Apple trees are typically 4–12 m tall at maturity, with a dense, twiggy crown.
The leaves are 3–10 cm 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. Apples require cross-pollination between
individuals by insects; all are self-sterile, and self-pollination is
impossible, making pollinating insects essential. 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 1–4 cm diameter in most of the wild species, to 6 cm in M. sylvestris
sieversii, 8 cm 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.
Cultivation For the Malus domestica cultivars, the
cultivated 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, of which 'Evereste' and 'Red Sentinel' have gained 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. Crabapples are small and sour tasting,
and visually resemble a small apple, particularly some apples known as the
"Lady Apple" AKA Pomme d'Api, Lady's Finger, Wax Apple and Christmas Apple.
Uses Crabapple fruit is not an important crop
in most areas, being extremely sour and woody, and is rarely eaten raw for this
reason. In some southeast Asian cultures they are valued as a sour condiment,
sometimes eaten with salt and chilli pepper, or shrimp paste.
Some crabapples 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. Because of the plentiful blossoms and
small fruit, crabapples are popular for use in bonsai culture.
Species Cultivars
Malus × moerlandsii Door. 'profusion' - Profusion crabapple
References Germplasm Resources Information Network:
Malus Flora of China: Malus
Virginia Cooperative Extension - Disease resistant crabapples Archived 8 February
2007 at the Wayback Machine The PRI disease resistant apple breeding
program: a cooperative among Purdue University, Rutgers University, and the
University of Illinois.