More info on Spiranthes sinensis

Japan has one truly weedy orchid species, Spiranthes sinensis.  This is a remarkable plant for many reasons, not the least of which is its startling purple-pink color.  It is one of the few orchid species that has actually benefited from human activity, in particular the clearing of forests and creation of grassy areas where it thrives.  Let’s take a closer look at this fascinating plant.

Spiranthes sinensis is a short-lived perennial plant, growing singly or in small clumps, and capable of forming colonies of thousands of individuals.  In mid-fall a small rosette of bright green leaves form around a central growing point. They are held close to the ground and are 3-6 cm long and 1-1.5 cm wide.  In the cold winter months they stop growing but remain green.  Starting in late March they begin to grow again and by May or June have elongated up to 12 cm and increased in number.

Sometime in late June the unbranched flower spike begins to grow from the central growing point and by mid-July is standing 15-40 cm tall and sporting anywhere from a handful of flowers to several dozen.  The flowers are arranged in a helix around the spike, and flower sequentially.  The flowers are small, no more than 6 mm across.  The sepals and petals are long and point forward with the dorsal sepal and two petals forming a little hood over the lip.  They range from pale pink to deep lavandar in color.  The lip is relatively broad and tongue-like in shape and recurves downward.  It is frilled and pure white.  The overall look of the tiny flowers is crystalline.  Albino forms exist, but why would you want to have just another white Spiranthes?

Seed formation is rapid, probably taking just a few weeks.  By the time of flowering the leaves are all but spent, and after flowering they disappear completely only to regrow a few months later.

These lovely plants range over all of Japan, the Korean Peninsula, part of Russia, and also China.  They favor open, sunny, grassy areas such as roadsides, fields, the berms of rice patties, and lawns, but also grow in bright shade just within the eves of a forest.  It is a common volunteer plant in garden beds and flower pots as long as these are sunny and moist.

In cultivation the plants will show new growth in late summer after flowering.  In habitat they tend to go semi-dormant until mid-fall when they’ll send up a few new leaves, forming a compact rosette.  These will persist all winter until the warm weather comes at which point they grow fast culminating in flowering by mid July.

Because of this growth cycle, I keep mine in bright conditions year round, but only fertilize them when in active growth. They will grow in any well draining compost, but I’ve even seen a few come up in my bog gardens.  They seem to prefer good drainage, but constant moisture as well.

Given the range of this species, it seems indifferent to temperature, though I’m sure that local variants exist, so not all plants will have equal cold hardiness.  In nature they are found from USDA cold hardiness zones 3-11, the equivalent of south Florida to Labrador!  So, sourcing the right plants for your conditions is probably important.

A dainty little plant and worth growing. This is one weed you won’t mind growing in your garden.