Apple

What is an apple?

The apple is one of the most widely grown fruit trees of the temperate world, and in most people's minds a tree of cool, green landscapes. Yet its origins lie in the dry mountains of Central Asia, and some of its varieties are at home in places with hardly any winter. That range is what makes it interesting for a Mediterranean slope.

Origin and growth

The cultivated apple descends mainly from Malus sieversii, the wild apple of the Tian Shan, where it still forms whole forests. On its way west along the old trade routes it crossed repeatedly with the European crab apple, Malus sylvestris. A study by Cornille and colleagues showed that this secondary contribution was so large that today's apple is genetically closer to the crab apple than to its Central Asian ancestor.

The Royal Horticultural Society gives 4 to 8 metres for most cultivated varieties. Rootstock decides much of the final size, from a small bush to a full standard tree.

Requirements

Winter chill. Most apples need a considerable amount of winter cold; UF/IFAS gives 200 to 1,000 chill hours. Without it, buds open late and unevenly and fruit set is poor. Low-chill varieties such as 'Anna' (about 200 hours), 'Dorsett Golden' and 'Ein Shemer' (about 100 hours each, according to the University of Arizona) shift that limit.

Cold. The wood is very winter-hardy. The blossom is sensitive: at full bloom about ten percent of flowers are lost at around -2.2 °C and ninety percent at around -3.9 °C, according to Washington State University.

Water. Apples need regular water while the fruit grows. In a dry summer a mulched root zone and a site that collects water make the difference.

Soil and light. Deep, humus-rich, well-drained soil; full sun for good fruit.

Fruit, use and harvest

Depending on the variety, apples ripen from early summer to late autumn; low-chill varieties such as 'Anna' are among the early ones. They are eaten fresh, cooked, dried, pressed for juice or fermented into cider. Late varieties keep for months in a cool store.

Most varieties need pollen from another variety flowering at the same time. 'Anna' can set some fruit on its own, but bears better with 'Dorsett Golden' or 'Ein Shemer' as partners.

Caution. Apple seeds contain amygdalin; a study of fifteen varieties found 1 to 4 milligrams per gram. Seeds swallowed whole usually pass through, crushed seeds in quantity should not be eaten.

In the food forest

In a food forest the apple usually belongs to the low tree layer, on medium rootstocks beneath taller canopy trees. Around it, a plant guild of nitrogen-fixing shrubs, flowering herbs and ground cover can feed the soil and attract pollinators. Fallen leaves and prunings stay on the ground as mulch. An apple orchard with grass, herbs and grazing animals beneath it is a traditional form of polyculture in Europe.

In the Mediterranean climate

Where the Mediterranean meets mild winters, the apple runs into its chill requirement. Israel answered with breeding: at Kibbutz Ein Shemer, Abba Stein bred 'Anna' to grow an apple like Golden Delicious in an almost subtropical climate. Together with 'Dorsett Golden' and 'Ein Shemer' it is now recommended for warm-winter regions such as the low desert of Arizona.

Sardinia once had a wealth of its own apples. The University of Sassari estimates that genetic erosion has reduced the island's local apple varieties by about 57 percent. Among those listed as threatened are Appio, Limoncella, Miali, Rosa, Santu Giuanni, Sonadore and Trempa orrubia. They were selected over generations under island conditions.

The apple is not on the EU list of invasive alien species.

Propagation and care

Apples do not come true from seed, so varieties are grafted onto rootstocks; seedlings are useful as vigorous rootstocks or for hedgerows. Winter pruning shapes the crown, summer pruning calms strong growth. In the first summers young trees need water and a mulched root zone.

How Terra Humana understands it

At Sa Medada the apple is a test of how far a tree of cool landscapes can be carried into a mild climate. Low-chill varieties make such a test possible, and the old Sardinian apples show that the island once had its own answers. In the food forest it is meant to take the place of a modest, long-lived fruit tree in the low tree layer, surrounded by plants that feed the soil it stands in.