Calanthe sieboldii - Garden orchid

Calanthe sieboldii is a beautiful terrestrial orchid that comes from Japan, which is a bit tricky to grow. It is a perennial, flowering and vigorous plant that produces a floral stem carrying large, pale yellow to lemon yellow, long-lasting, flowers in late spring sometimes speckled with brown on the labellum and more or less fragrant depending on the plants. It is best grown in mild and humid climates, in thick and well-drained humus, remaining moist from spring to the end of summer,  but dry in winter, and in partial shade. Growing in pots allows for easier control of the composition and humidity of the growing medium. In dry soil, protected by mulch, it can withstand temperatures down to around -10 °C.

Originally from Japan and very close to Calanthe discolor, the Calanthe sieboldii has the largest flowers among this group of Japanese orchids. Its flowering period is particularly long for a perennial orchid. This species grows in humid forests, along mountain streams and wet slopes, in high mountain meadows and among the thickets of the warm and humid regions of western Japan.

The deciduous vegetation emerges from the ground in spring and dries up in autumn. The plant forms a tuft of foliage about 35 cm (14in) in all directions. This orchid develops a pseudobulb, from which large light green leaves, measuring 15 to 40 cm (6 to 16in) long and 8 to 15 cm (3 to 6in) wide, emerge in early spring. They are pleated and broadly ovate, with strongly impressed parallel veins. The foliage resembles that of veratrum. In late spring, around May-June, the plant produces beautiful inflorescences reaching a height of 45 cm (18in), bearing 5 to 25 pale yellow to bright lemon yellow flowers, measuring 3 to 5 cm (1 to 2in) in diameter and fragrant. They are widely open, composed of elongated, slightly pointed sepals and petals and a trilobed labellum (lip). The central lobe is deeply veined and has a variable number of linear protrusions. Some plants have reddish-brown marks on the underside of the column and the projections of the lip. The root system is weakly suckering. The plant goes dormant in winter when its foliage has completely turned yellow.

In favourable climates, plant Calanthe sieboldii in partial shade, sheltered from the wind, in light, humus-rich soils, tending towards neutral or slightly acidic. Plant it in the shade in a cool rockery between rocks, or at the edge of a cool understory alongside Arisaema, Cypripedium, Paris, Bletilla and ferns. Given its poor hardiness, it will be necessary to protect the root system from harsh winter conditions and excess moisture. This plant grows well in large pots, which can be overwintered in a cold greenhouse.

When receiving your orchids, handle them with care: these plants produce few roots and are delicate!