Japanese persimmon

Identification and origin

Diospyros kaki belongs to the Ebenaceae, the ebony family. Its native range stretches from Assam to central and southern China, Vietnam, Hainan and Taiwan. It has been cultivated for so long that it has become naturalized elsewhere, notably in Japan and Korea, where it has become a symbol of perseverance and good fortune.

It is a dense deciduous tree, upright at first and then rounded and spreading, with a moderate growth rate. In cultivation it usually reaches 19.5–29.5 ft tall and 15–24.5 ft wide; in good conditions it can climb as high as 26–39.5 ft over twenty to fifty years. Semi-dwarf varieties stay much shorter, around 6–8 ft.

The alternate leaves, oval to obovate, measure 3–6 in and sometimes up to 8 in. They emerge yellowish green in spring, turn dark green and glossy in summer, and then shift to yellow, orange, red and sometimes purple in fall. The gray-brown bark cracks deeply into rectangular or square plates that look very striking in winter.

The small, bell-shaped, cream to pale yellow, fragrant flowers appear in spring or early summer, after the leaves come out. The species is most often dioecious: female flowers are solitary, while male flowers are grouped in threes and tinged with pink. Some trees, however, carry male, female and sometimes perfect flowers on the same plant, and most cultivated varieties set fruit on their own, even without pollination, producing seedless fruit.

The fruit is a berry with a four-lobed calyx, round, oval or flattened like a tomato, 2–4 in across. It ripens from late summer into fall and can stay on the tree into winter. There are astringent varieties, such as ‘Hachiya’, which should only be eaten when very soft, and non-astringent varieties, such as ‘Fuyu’, which can be eaten while still firm. A young tree starts bearing at around four to six years old.

Light

The Japanese persimmon needs full sun, at least six hours of direct light a day. A south- or west-facing spot, sheltered from cold winds, helps both fruit set and ripening. In shade, flowering and the harvest drop off noticeably.

Watering

Once well established, the Japanese persimmon tolerates short dry spells, but it produces better with regular watering. During the first year, and after that whenever the weather is dry, check the soil moisture at the base of the tree before watering: soil that dries on the surface but stays moist deeper down is ideal. Its needs are greatest during spring growth and in summer, while the fruit is sizing up. A thick layer of mulch helps keep moisture even. Avoid standing water at all costs: the tree hates waterlogged soil.

Potting mix

It prefers deep, fertile soil that is moist but well drained, ideally a slightly acidic to neutral loam with a pH of around 6 to 6.5. It does tolerate clay, sand and more alkaline soils, though, as long as water drains away. Heavy, wet soils encourage root rot, to which the Japanese persimmon is very susceptible. Avoid overfeeding at all costs: too much fertilizer makes the fruit drop.

Temperature

The Japanese persimmon grows in USDA zones 7a to 10b. It withstands temperatures down to about 10 °F, but it can be damaged or killed below that, especially if the cold arrives after a mild spell in winter. Shelter it from cold winds. Late spring frosts damage the flowers, and an early fall freeze spoils fruit that is still unripe. Some varieties, such as ‘Great Wall’, ‘Korean’ or ‘Sheng’, are known to be more cold hardy; ‘Fuyu’, on the other hand, is sensitive to cold. This is not an indoor tree.

Repotting

The Japanese persimmon is mostly planted in the ground. Semi-dwarf varieties, which stay under 8 ft, are better suited to small gardens and large containers. Plant in well-drained soil, in full sun, leaving enough room for the mature spread. Regularly remove the suckers that sprout from the base, especially on a grafted tree. The species can also be grown as an espalier, a hedge or a screen, and it is a classic subject for the art of bonsai.

Pruning

No yearly pruning is essential. For a fruit tree, training it on a central leader carrying three to five scaffold branches spaced about 12 in apart, the first one around 3 ft above the ground, gives it a sturdy structure. After that, prune in winter, while the tree is dormant: remove dead or damaged wood, crossing branches and narrow crotches. Fruit forms on the current season’s shoots.

Propagation

Fruiting varieties are propagated by grafting or budding, because seedlings do not faithfully reproduce their traits. The most widely used rootstock is the American persimmon (Diospyros virginiana), well adapted to warm regions; Diospyros lotus is also used. The choice of rootstock matters: it can influence fruit retention and ripening time, and some Diospyros species are incompatible. Growing from seed, sown as soon as it is ripe, is mainly used to produce rootstocks or ornamental trees.

Common problems

• Fruit drop: some drop a few weeks after flowering is a natural thinning. Heavier drop, common with seedless fruit, is triggered by stress: too much fertilizer, heat, cold, overwatering or drought. Mulch and regular watering reduce it without stopping it entirely.
• Alternate bearing: a large crop is often followed by a leaner year.
• Early leaf drop: fungal leaf spots can make the leaves fall ahead of time, which delays or halts ripening.
• Diseases: anthracnose, powdery mildew, twig dieback, crown gall and, more rarely, armillaria root rot; root rot threatens poorly drained soils.
• Pests: scale insects, mealybugs, persimmon psyllid, leafrolling or defoliating caterpillars, thrips, mites and wood borers. Birds, deer and small mammals love the ripe fruit.

The same symptom, such as leaf or fruit drop, can have several causes: look at the soil moisture, any recent fertilizing and the weather over the past few weeks before taking action.

Toxicity

No toxicity has been reported for dogs, cats or horses. The fruit is edible, provided you wait for astringent varieties to become fully ripe. Eaten in very large quantities, however, persimmons can form a compact mass of fiber and tannins in the stomach that can cause an intestinal blockage, especially in older adults, people with diabetes or people who have already had stomach surgery.