Prunus incisa aka Fuji Cherry

Prunus incisa is moderately easy to grow in appropriate conditions. It thrives in most garden soils with good drainage and tolerates chalk, clay, loam, and sand. The main challenges are its susceptibility to several diseases including silver leaf, bacterial canker, blossom wilt, and honey fungus. Proper placement in full sun with shelter from strong winds helps ensure healthy growth, and summer pruning rather than winter pruning reduces silver leaf infection risk.

Prunus incisa is a slow-growing deciduous tree or large shrub reaching 4-8 metres in both height and spread over 10-20 years. It has a spreading, rounded habit with an elegant form. Young specimens are often shrubby, developing into a small tree with age. The compact cultivar 'Kojo-no-mai' reaches only 1.5-2.5 metres, making it suitable for smaller gardens or container growing.

Prunus incisa is exceptionally cold-hardy, tolerating temperatures down to -20°C (RHS hardiness rating H6). It is suitable for all UK regions and northern Europe, and thrives in USDA zones 5-7. While extremely cold-hardy, it benefits from a sheltered position protected from strong winds and late spring frosts that could damage early flowers.

Prunus incisa can be propagated by seed or vegetative methods. Seeds require 2-3 months cold stratification and should be sown outdoors in autumn or stored cold for spring sowing; germination may take up to 18 months. Softwood cuttings can be taken in spring to early summer with bottom heat, or semi-ripe cuttings with a heel in July-August. Commercial propagation often uses budding in late summer or grafting in late winter.

Prunus incisa produces abundant saucer-shaped flowers in early spring (March-April), before the leaves emerge. The delicate blooms are white to pale pink, approximately 2cm across, appearing in clusters of 2-4 on short stalks. The petals are notched at the tips, and the wine-red calyx provides an attractive contrast. Flowers are sometimes followed by small purple-black cherry-like fruit approximately 8mm in diameter.

Prunus incisa has hermaphroditic flowers (containing both male and female parts) and is pollinated by insects. It is recognized as an RHS Plant for Pollinators, providing valuable early-season nectar and pollen for bees and other pollinating insects at a time when few other flowers are available. The early spring bloom makes it particularly important for emerging pollinators.

Several Prunus incisa cultivars have gained the RHS Award of Garden Merit. 'Kojo-no-mai' is a compact variety (1.5-2.5m) with distinctive zigzag branches and excellent autumn colour. 'The Bride' is noted for profuse white flowers. 'Praecox' flowers in winter. 'Oshidori' and forma yamadei are also notable. The species has been crossed with Prunus speciosa to create 'Umineko', and with other species to produce the popular hybrid 'Okame' with carmine-pink flowers.

Prunus incisa is exclusively an outdoor plant, thriving in USDA zones 5-7 and all UK hardiness zones. It requires the winter cold period for proper dormancy and flowering. Plant in full sun to partial shade in a sheltered position protected from strong winds. It tolerates various soil types provided drainage is good. In Japan, it grows wild in mountain woodland habitats around Mount Fuji and Hakone.

Prunus incisa requires minimal pruning (RHS Pruning Group 1). When young, remove crossing or badly placed branches to establish a good framework. Mature trees need little pruning beyond removing dead, damaged, or diseased wood. Crucially, prune in summer rather than winter to reduce the risk of silver leaf disease infection. Avoid heavy pruning as cherries do not respond well to hard cutting back.

In spring, enjoy the early blossom display and protect flowers from late frosts if possible. Summer is the time for any necessary pruning to avoid silver leaf infection. Autumn brings attractive orange-red foliage colour before leaf drop. Winter requires no special care for established trees as they are extremely cold-hardy to -20°C. Apply mulch around the base to retain moisture and suppress weeds, but keep it away from the trunk.

Prunus incisa is susceptible to several pests and diseases. Common pests include aphids, caterpillars, and bullfinches which may damage flower buds. Diseases to watch for include silver leaf (prune in summer to reduce risk), bacterial canker, peach leaf curl, blossom wilt, and honey fungus. The cultivar 'Kojo-no-mai' may also develop witches' broom caused by Taphrina wiesneri. The species is listed as a high-risk host for Xylella fastidiosa.

The small purple-black fruits of Prunus incisa are edible raw or cooked, though they measure only about 8mm with a single large seed, leaving little flesh. Seeds can also be eaten but should be avoided if they taste bitter, as bitterness indicates higher levels of cyanogenic compounds. Like all Prunus species, leaves and seeds contain hydrogen cyanide, so excessive consumption should be avoided.

Beyond its primary ornamental value, Prunus incisa has limited other uses. The leaves produce a green dye, and the fruit yields a dark grey-to-green dye. In Japan, it has traditionally been cultivated as a dwarf potted specimen (similar to bonsai). While the wood has no industrial value, the tree is excellent for hedging and makes a beautiful specimen plant in gardens.