Sapium japonicum

Sapium japonicum (synonym Neoshirakia japonica) is a relatively unknown bush that deserves to be planted more often for its fantastic autumn colours. Its green leaves turn crimson red during the first cold weather, making Sapium one of the best ornamental plants for autumn. Its summer flowering and its fruits are nondescript, but its autumn splendour is worthwhile. More hardy than frequently stated, this bush seems to resist, according to certain sources, down to approximately -12 °C, or even more, which is adequate for many regions. Humus-rich, acidic or neutral soil that remains slightly moist will suit it perfectly.

Sapium japonicum, sometimes nicknamed Japanese Tallow Tree,  is a member of the very large Euphorbiaceae family. This family includes more than 6000 species distributed in all areas of the globe, except the Arctic and Antarctica. Euphorbiaceae produce latex that can be irritating or even toxic.

Originally from the Far East, Sapium comes to us from the humid forests of China, Korea, and Japan: it is a species of moist undergrowth. In its original habitat, it forms a small tree about 7 or 8 m (23 or 26ft) tall, with fairly slow growth, growing in low-altitude mountainous areas, from 100 to 400 m (328 to 1312ft). In our gardens, it is a bush that reaches a height of 3 m (10ft) with a spread of 2 m. Its leaves measure from 7 to 16 cm (3 to 6in) long, 4 to 8 cm (2 to 3in) wide, and are elliptical or ovate in shape. The upper surface is glossy green, the lower surface is paler. A short petiole (2-3 cm (1in)) connects them to the grey-brown, smooth, and slender branches. Between May and July, it produces inflorescences from 5 to 11 cm (2 to 4in) long, in the form of spikes consisting of numerous small male flowers at the top and a few female flowers at the base. These yellow-green inflorescences are graceful but quite insignificant. They develop into yellow fruits speckled with brown, small 3-lobed capsules measuring 10 to 15 mm (1in) in diameter, which ripen in September and then open to project their seeds a fair distance. When autumn and its cool nights arrive, the foliage turns crimson red, before falling. Caution, this plant contains toxic parts. It is generally free from any disease or insect attack.

This species appreciates moist soil and grows in acidic to neutral conditions, in humus-rich soil. These soil requirements are ultimately more limiting than its hardiness, which is better than often stated. This plant has been successfully tested in cold regions such as Burgundy or Pennsylvania in the United States, as well as in Belgium (Arboretum Wespelaar).

In the garden, Sapium japonicum enchants in autumn with its fiery colours. In a sufficiently large garden, it can be planted in the foreground of a Cercidiphyllum japonicum, the caramel tree, whose lovely heart-shaped leaves will associate with the explosion of colours from Sapium in autumn. In a smaller area, the Fothergilla major can be chosen, which shares the same cultural requirements as Sapium and turns red, orange, and yellow at the end of the season. Essential for yellow tones, the Ginkgo will perfectly complement the red of Sapium, especially with the dwarf variety Mariken, well-suited to small spaces.