|Malus 'Purple Prince'|
Malus (// or //), apple, is a genus of about 30–55 species of small deciduous trees or shrubs in the family Rosaceae, including the domesticated orchard apple (M. domestica). The other species are generally known as crabapples, crab apples, crabs, or wild apples.
Apple trees are typically 4–12 m (13–39 ft) tall at maturity, with a dense, twiggy crown. The leaves are 3–10 cm (1.2–3.9 in) 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).
Apples require cross-pollination between individuals by insects (typically bees, which freely visit the flowers for both nectar and pollen); all are self-sterile, and (with the exception of a few specially developed cultivars) 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 (0.39–1.6 in) diameter in most of the wild species, to 6 cm (2.4 in) in M. sylvestris sieversii, 8 cm (3.1 in) in M. domestica, and even larger in certain cultivated orchard apples; among the largest-fruited cultivars (all of which originate in North America) are 'Wolf River' and 'Stark Jumbo'. The centre of the fruit contains five carpels arranged star-like, each containing one to two (rarely three) seeds.
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. Because of the plentiful blossoms and small fruit, crabapples are popular for use in bonsai culture.
Crabapple fruit is not an important crop in most areas, being extremely sour and (in some species) 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.
Crabapple has been listed as one of the 38 plants that are used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".
- Malus × moerlandsii Door. 'profusion' - Profusion crabapple
- Cirrus Digital Purple Prince Crabapple
- Potter, D., et al. (2007). Phylogeny and classification of Rosaceae. Plant Systematics and Evolution. 266(1–2): 5–43. [Referring to the subfamily by the name "Spiraeoideae"]
- Sunset Western Garden Book, 1995:606–607
- Phipps, J.B. et aL. (1990). "A checklist of the subfamily Maloideae (Rosaceae)". Can. J. Bot. 68 (10): 2209. doi:10.1139/b90-288.
- Ken Wilson and D.C. Elfving. "Crabapple Pollenizers for Apples". Ontario Ministry of Agriculture and Food. Retrieved 12 Sept 2013.
- "Macro video of a Malus Evereste apple on a tree in winter". YouTube.
- "RHS Plant Selector - Malus 'Evereste'". Retrieved 20 July 2013.
- "RHS Plant Selector - Malus 'Red Sentinel'". Retrieved 20 July 2013.
- Apple Tree Rootstocks Ecogardening Factsheet #21, Summer 1999
- Alaska Department of Natural Resources
- "The Growing Guide". Stark Bro's Nurseries & Orchards Co.
- Rombauer, I.; Becker, M. R., & Becker, E. (2002) . All About Canning & Preserving (The Joy of Cooking series). New York: Scribner. p. 72. ISBN 0-7432-1502-8.
- "The Science of Cidermaking". Andrew Lea. Retrieved November 2013.
- Fraser, Anna (22 August 2005, 17 July 2008). "Properties of different trees as firewood".
- D. S. Vohra (1 June 2004). Bach Flower Remedies: A Comprehensive Study. B. Jain Publishers. p. 3. ISBN 978-81-7021-271-3. Retrieved 2 September 2013.
- "Flower remedies". Cancer Research UK. Retrieved September 2013.
- 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.
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