An unusual and attractive plant that doesn’t quite look like a fern is Sphenomeris chinensis. While few westerners have even heard of this fern, it is in fact a common plant in much of east Asia and Polynesia. Its 3-pinnate fronds and tiny wedge shaped pinnules give it a uniquely delicate look and has earned it the common name lace fern.
S. chinensis is a fairly small evergreen fern with a short creeping rhizome. Fronds are produced throughout the warm months and are 3 times pinnate giving them a very fine textured look. Frond length is variable depending on the exposure to the sun with long fronds growing in shadier locations. They can be anywhere from 10-100 cm long and 8-20 cm wide, but typically don’t grow more than 50 cm long. Although the pinnae grow in an alternating pattern, there often exists a basal pair of pinnae that are separate from the next pair further up the rachis by several centimeters.
These basal pinnae are the largest on the frond and the rest get progressively smaller as they approach the tip of the blade giving the frond a long triangular shape. The tiny pinnules are wedge shaped with the wide end at their terminus. At the end of the pinnules the small oval sori are born singly or in pairs. The reddish-brown stipe is completely scaleless and hairless, and accounts for nearly half of the frond length on large fronds. These ferns are commonly seen growing in loose colonies on nearly vertical slopes.
S. chinensis is found in the warmer areas of Japan including Honshu (Niigata, Yamagata, and Fukushima Prefectures and southward), Shikoku, Kyushu, the southern islands to Okinawa, as well as Korea, Taiwan, China, Indochina, the Philippines, Papua New Guinea, India, Nepal, and the South Pacific Islands (Hawaii, Cook Islands, Tonga, Marquesas Islands, and Samoa). It perhaps has been reported from Madagascar, but this may be a mistaken record. It is listed as a potential exotic weed in New Zealand.
This lovely little fern can be seen in any moist forest in moderate to light shade, however it is also found on sunny roadsides in thick growth of grasses, herbs, and small shrubs. It seems to like to colonize raw earth in cuts created by roads, paths, and landslides, and also on natural rock outcrops where moisture is abundant. Seen from near sea-level to 1000+ m, but most common in low to mid elevations, 50-600 m, on Kyushu.
At first glance with its 3-pinnate fronds it can seem to be a Selaginella, but a closer look shows that it is indeed a type of fern. The frond’s shape is unusual, especially with its numerous, tiny wedge shaped pinnules. The overall appearance of the fronds is very soft and pleasing. It is mostly found in bright locations, from sunny roadsides to bright woods along stream banks, and is a common species in the Fukuoka area. In the fall and winter the fronds can get purplish if in an exposed position, thus adding to its charm.
Happily, it is easy to grow. I’ve had one in the garden for several years now and have given it no attention except to make sure that surrounding plants don’t out-compete it. In fact the only problem I’ve had is that it grows too well, so it is necessary to prune back larger fronds from time to time. This is a fern that requires bright light to grow well, and also needs a well drained, yet continuously moist soil. In nature you never see it in a flat place, so drainage is sharp. It is not fussy, so any reasonable woods loam is fine for this one. One drawback is its lack of cold tolerance, perhaps only hardy to USDA cold hardiness zones 7-10. It is a lovely compact growing fern if grown in bright light, but more airy and large in darker conditions.
Its Japanese name is horashinobu, meaning “cave Davallia” from the words hora (“cave”) and shinobu, the name for the epiphytic fern Davallia mariesii, which it not only resembles, but is related to. Another typically obscure Japanese name! The genus name, Sphenomeris, is from the Greek words spheno meaning a wedge and meris meaning a part, probably referring to the wedge shaped pinnules.
I have only praise for this lovely fern. If you can get one, do so. They are lovely to look at, easy to accommodate, and compact in size – in short, a must have plant for the serious fern collector or warm climate gardener.