Sweet Cherry

What is a sweet cherry?

The sweet cherry is the fruit tree of early summer: smooth, reddish-brown bark with horizontal bands, white blossom in spring before or with the leaves, and fruit that is among the first tree fruits of the year. It belongs to the rose family. In Europe its wild form grows along woodland edges, and birds have spread it for so long that its botanical name, avium, simply means "of the birds".

Origin and growth

Prunus avium is native to Europe, western Asia and parts of North Africa. In the forest the wild cherry grows into a tall tree; the Woodland Trust and Forestry England give up to 30 metres. Cultivated trees are much smaller, depending on rootstock and pruning. The sour cherry, Prunus cerasus, is a separate species.

Requirements

Winter chill. This is the cherry's main question in the south. Without enough cold the tree flowers late, unevenly and sparsely. In Morocco ten cultivars needed 662 to 929 chill hours. In Apulia the requirements ranged from 58 chill portions for 'Burlat' to 84 for 'Ferrovia', all of them still met at the study site.

Cold. The wood is winter-hardy; the weak point is the blossom. 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. Steady moisture while the fruit develops. Rain shortly before harvest makes ripe cherries crack. Waterlogged soil is not tolerated.

Soil and light. Deep, well-drained soil and full sun.

Fruit, use and harvest

Cherries ripen from late spring to early summer, some weeks after flowering. They are eaten fresh, preserved, dried or made into jam and liqueur, and they keep only a short time once picked. Birds harvest along with people.

Most sweet cherry varieties are self-incompatible and need a suitable partner variety flowering nearby.

Caution. The kernels inside the stones contain amygdalin, which releases hydrogen cyanide when crushed. Swallowed whole, a stone passes through; crushed kernels should not be eaten.

In the food forest

In a food forest a cherry on a vigorous rootstock is a canopy tree, tall and light-crowned, under which shade-tolerant shrubs and herbs can grow. On weaker rootstocks it belongs to the low tree layer. Its early blossom feeds bees at a time when little else flowers. In syntropic agriculture it would be one of the longer-lived trees, planted together with faster pioneers that shelter it and are later cut back as mulch.

In the Mediterranean climate

Around the Mediterranean, sweet cherries are mostly grown where winters are reliably cold: in mountains and hills. Sardinia has its own cherry villages. Burcei, in the hills north-east of Cagliari, has held its cherry festival since 1954; according to L'Unione Sarda, orchards there cover about 75 hectares with 21,000 trees. In Bonarcado the first orchards were planted below the village more than seventy years ago, and later ones on hills at 600 to 700 metres. The University of Sassari lists local cherry varieties threatened by genetic erosion, among them Addosa, Bianca (also Bianca di Aritzo), Carrufale di Bonnanaro, Corittu, Furistera and Nera di Villacidro.

Warming winters are already noticeable. In the Ebro Valley near Zaragoza, chill has fallen by six to eight chill portions since 1980, and the winter of 2023 to 2024 brought the lowest chill in fifty years, with delayed flowering in all 22 cultivars studied. Low-chill varieties from California are one answer; in a trial near Adana in southern Turkey, with around 540 to 650 chill hours, some of them bloomed in early March and were harvested in late April.

The sweet cherry is native to Europe and not on the EU list of invasive alien species.

Propagation and care

Varieties are grafted onto seedling cherry or on weaker rootstocks. Seedlings from stones grow vigorously but bear unpredictable fruit. Pruning is best done in summer after harvest, when wounds heal quickly. A mulched root zone keeps the soil evenly moist in the first summers.

How Terra Humana understands it

At Sa Medada the cherry is an experiment with the edge of its range. A tree that depends on cold winters is planted where winters are mild, and whether it flowers reliably will show how much chill this place gives. If it succeeds, it could become a light-crowned tree in the food forest that flowers early for the bees. The old Sardinian varieties, adapted over generations to the island, are a reminder that such adaptation has happened before.