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Sofora of Japan

Generality

The Japanese Sofora (Sophora japonica) is a tree of high ornamental value that belongs to the Fabaceae family (legumes) which reaches 200 years of life. It is originally from China and Korea. On average on 10-15 meters, it can exceed 20 meters in height, with an initially faster growth that slows down later. The erect stem tends to become more twisted and wrinkled with time, the shape of the crown is rounded and expanded and reaches a width of 4-8 meters, with greenish gray branches that have the tendency to grow downwards and darken with the years go by. The bark is wrinkled with prominent cracks, gray-brown in color. The deciduous and pinnate leaves are up to 25 cm long, with 7-17 ovate leaflets, initially whitish, then glossy dark green on the top and blue-green and hairy on the bottom. They turn golden yellow in autumn, before falling off. The papilionaceous flowers, which contain an active ingredient called rutin (from which the troxerutin used in the therapy of capillary fragility is obtained), are hermaphroditic, yellowish-white and fragrant, gathered in racemes in turn grouped to form panicles that hang from the end of the branches. Flowering, which begins when the plant has already reached maturity, so no earlier than 10 years of life, begins in the summer between June and July and lasts until the beginning of autumn. The fruits are fleshy lomenti, first translucent green then brown when ripe (December), with different bottlenecks between one seed and another that make them similar to necklaces. Despite being a plant from desert regions, it has a fibrous but deep root system. It has recently been discovered that the extract of the flowers and buds of the plant has a curative effect in case of cerebral infarction, thanks to its anti-haemorrhagic and anti-haemostatic action. Its pollen is not allergenic.

Climate and terrain

In Italy its distribution range reaches 500 m above sea level. It gives its best on fertile and well-drained soils, in full sun, but it can tolerate well even exposures of partial shade and less generous soils. It fears prolonged stagnation and too compact soils. It easily bears very cold temperatures, down to -20 ° C, and can tolerate a certain degree of salinity without problems.

Plant

The propagation of the plant can take place from seed, but this involves a long wait before being able to see the flowering, in some cases up to 30 years depending on the climate. The seeds must be treated at high temperatures or with acids before they can be used, although some manage to obtain a reasonable percentage of germination by planting the seeds immediately after they have been harvested. For seeds that have been harvested for a long time, however, it is usually sufficient to pour boiling water over them and leave them to soak for a day. Sowing takes place in March, in a heated greenhouse. The transplant or implantation can take place both in autumn and in spring, using stakes in the case of plants with particularly thin stems. Some varieties and cultivars such as the pendula cannot be propagated from seed,

Cultivation techniques

The sofora is a fascinating tree all year round, suitable as an isolated specimen in large parks or large gardens, but is also used in the urban context as a road tree given its optimal resistance to pollution. In medium-small gardens it is used by exploiting the slowness of its growth, but it must be borne in mind that the more the tree grows, the denser the shadow it casts becomes. At maturity the shadow cast by a Sophora is very dark. Furthermore, the plant drops flowers, leaves, pods from July to December, and by attracting the birds that eat its fruits, even the excrements are to be considered. It does not need pruning, except that necessary to eliminate dead or damaged branches. If necessary, a slow release granular fertilizer can be administered over the entire