Crabapples

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, 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 (which like the genus derives from the Latin name mālum), 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.
en.wikipedia.org

https://en.wikipedia.org/wiki/Malus