Cyclosorus interruptus
Thelypteridaceae or Marsh fern family
Synonyms: Aspidium gongylodes, Aspidium resiniferum, Aspidium unitum, Christella interruptus, Cyclosorus gongylodes, Dryopteris gongylodes, Dryopteris interrupta, Nephrodium resiniferum, Polystichum gongylodes, Pteris interrupta, Thelypteris gongylodes, Thelypteris interrupta
Neke
Hottentot fern, Swamp cyclosorus, Swamp shield-fern, Willdenow's maiden fern
Natural Range & Environment
Cyclosorus interruptus has a wide distribution throughout the Indo-Pacific and is found in Sri Lanka, southern India, Burma to Indochina, Malaysia to the Philippines, Australia, New Zealand (near hot springs on the North Island), and many Pacific islands, as well as the New World tropics and subtropics. In Hawai‘i, it is indigenous to all the main islands except Ni‘ihau and Kaho‘olawe [Flora of the Hawaiian Islands]. Neke grows in freshwater marshes, fens, bogs, mucky wetlands, and abandoned kalo (taro) patches from near sea level to 1,070 m (3,510 ft) [Palmer 2003].
Mature Cyclosorus interruptus frond, upper surface. Close-up of the lower surface of a neke frond showing the V-shaped pattern of ripe sori. Mature cultivated neke.
Description
Cyclosorus interruptus is a creeping fern about two feet (61 cm) tall with olive-green fronds and a lifespan greater than five years. Its rhizomes (underground stems) spread through the mud or soil, periodically putting up leathery 1-pinnate (divided into leaflets on either side of a central stalk) fronds with deeply lobed pinnae (leaflets). The fronds have tiny white hairs and are normally 1½ to 2 feet (46 to 61 cm) long and about half as wide. The lobes of the leaflets are nearly triangular. Round (brown when mature) sori are arranged in a repeated V-shaped pattern along the margins on the underside of the frond. According to Kay Lynch, a local native Hawaiian fern expert [per. comm.], neke, when brushed against, crushed, or cut, has a pleasant scent reminiscent of newly-cut hay.
Growth Requirements
General
Cyclosorus interruptus is in the Marsh fern family with common names outside of Hawai‘i like the swamp shield-fern and swamp cyclosorus. Consider these names when planting, placing, and growing neke. Plant it on the margins of a pond or inside a water feature (see Marsilea villosa for the best way to do this), in a large container you can regularly flood, at the low point in your yard that always puddles when it rains, at the bottom of your home's gutter downspouts, or near the outside discharge port of your washing machine. Get the idea? However, consider too that while neke loves soggy soil or media, you really only have to keep the soil or media wet to keep it alive and growing. Therefore, other uses of neke include using it as a ground cover or for erosion control (e.g., stream restoration).
Cyclosorus interruptus is one of a few native Hawaiian ferns that grows well, maybe even best, in a site with full sunlight for all or most of the day (provided you always keep its roots wet). However, it will also survive in shaded sites like most other ferns. It doesn't seem to be picky about soil or media type as long as it remains wet; we have grown it in lava/cinder, clay, and organic-dominant soils and media.
Neke generally does not need to be fertilized except when kept in a container. There, provide it with a light foliar feeding of an organic or inorganic fertilizer every one to two months. Do not fertilize neke planted in or near ponds or streams, or inside a water feature since this can pollute the water and cause problems such as an algal bloom.
Under optimum conditions, neke can grow and spread fast, so be prepared to prune it back, dig it up, or otherwise contain it if it gets out of control. Otherwise, you need only remove any dead fronds to keep it looking nice. Propagating neke from spores is a serious challenge; therefore, it's much simpler to divide your existing plant if you want to create new neke for another site.
Pests and Diseases
We have only occasionally seen caterpillars chew on the fronds of neke; otherwise, this fern seems to be pest-free.
Uses
Ancient Hawaiian
In the past as well as today, the stiff fronds of neke were/are used to make lei [McDonald & Weissich 2003], maybe, in part, because of its hay-like fragrance.
Modern
See above.
Special Features and Information
General
Thelypteridaceae or the Marsh Fern family is one of the largest fern families with about 1,000 species worldwide [Palmer 2003]. Currently (2025), there are nine Thelypteridaceae species in six genera native (five endemic and one indigenous) to Hawai‘i [Flora of the Hawaiian Islands].
There is some question as to whether neke is actually indigenous to Hawai‘i or was inadvertently introduced by early Polynesians since it is commonly seen in abandoned kalo loʻi. St. John [1978] notes that these early explorers packed mud around kalo (taro) corms for oceanic transport, and the mud may have contained neke spores. St. John uses the synonym Thelypteris interrupta for neke in this 1978 article.
Hawaiian Name
Neke may be a variation of the word nakeke, which means "rustling," perhaps a reference to the stiff fronds rubbing together [Valier 1995]. According to Kay Lynch, a local expert on native Hawaiian ferns [per. comm.], Waineke Swamp in Kōkeʻe State Park on Kauaʻi was named for this fern.
Etymology
Cyclosorus comes from the Greek words kyklos, meaning "circle," and soros, meaning "heap," referring to the round sori on the undersurface of the plant's fronds [Palmer 2003]. The species name, interruptus, is Latin for "interrupted, not continued;" however, it's not clear how this meaning applies to this species [Palmer 2003].
BPK