Fimbristylis cymosa
subsp. spathacea &
subsp. umbellato-capitata
Cyperaceae or Sedge family
Synonyms:
For subsp. spathacea: Fimbristylis atollensis, Fimbristylis spathacea
For subsp. umbellato-capitata: Fimbristylis cymosa var. pyncocephala, Fimbristylis cymosa var. umbellato-capitata, Fimbristylis pycnocephala, Fimbristylis umbellato-capitata
Mauʻu ʻakiʻaki
Button sedge, Tropical fimbry
Natural Range & Environment
Fimbristylis cymosa is native to coastal areas across the Pacific Basin, including Australia, western Malesia, many Pacific islands, and the Neotropics. It has since spread to many other regions, such as Texas and Florida, via human introductions [PictureThis]. In Hawai‘i, the two subspecies have overlapping ranges. Subspecies spathacea is found from sea level to 10 m (33 ft) on Midway Atoll (Pihemanu), Laysan (Kauō), French Frigate Shoals (Kānemilohaʻi), Ni‘ihau, Kaua‘i, O‘ahu, West Maui, and Hawai‘i Island. Subspecies umbellato-capitata is found from sea level to 60 m (197 ft) on Kure (Mokupāpapa), Midway Atoll, Laysan, and all the main Hawaiian Islands except Kaho‘olawe. Mauʻu ʻakiʻaki grows on sandy beaches and in shallow sand or soil on and among rocks and cracks in lava [Wagner et al. 1990].
Three examples of mauʻu ʻakiʻaki subsp. umbellato-capitata in the landscape. Wild mauʻu ʻakiʻaki subsp. umbellato-capitata near the ocean. (Photographs of wild and along-the-sidewalk mauʻu ʻakiʻaki courtesy of Forest & Kim Starr CC BY 2.0.) A cultivated mauʻu ʻakiʻaki subsp. spathacea; Note the more widely-spaced inflorescence.
Description
Fimbristylis cymosa is a compact sedge that varies in size (from a few inches to nearly a foot [30 cm] tall and wide) depending on its habitat, with a lifespan normally greater than five years. It spreads horizontally via rhizomes (i.e., horizontal subterranean plant stems). Mauʻu ʻakiʻaki has stiff thin pointed leaves. Multiple flowering spikes grow out above the main plant, ultimately producing a terminal cluster of fruits that are rusty to grayish brown when ripe. The achenes (single-seeded fruits) are extremely small (1 mm) and numerous. Blooming is year-round in cultivation.
There are two subspecies of mauʻu ʻakiʻaki, subspecies spathacea and subspecies umbellato-capitata. The main difference between the two is the flowers/fruit spikelet. The flower/fruit clusters of spathacea are spread out, whereas umbellato-capitata has more compact tighter clusters (see photographs above). However, plants with intermediate characteristics have also been recorded. A third subspecies, cymosa, is not native to the Hawaiian Archipelago.
Growth Requirements
General
Fimbristylis cymosa is a good replacement for mondo grass (Ophiopogon japonicus) as a groundcover in sunny sites, and, because it is a xeric plant, it will require less water; space the plants 4 to 6 inches apart. Mauʻu ʻakiʻaki is also attractive as a potted plant. Use a media mix with good drainage (e.g., 50% cinder or perlite) and allow the media to dry between waterings. Other attractive (and practical) places for mauʻu ʻakiʻaki include rock gardens or between the paving stones on lightly-used pathways. A rumor we’ve heard but never tested is that the spiky leaves of many mau‘u ‘aki‘aki planted as a continuous groundcover will keep cats out of your yard.
Mauʻu ʻakiʻaki does best in a site with full sunlight for all or most of the day and will be shorter than a plant grown in partial shade. When first planted, keep the soil moist for the first two or three weeks. Then, slowly reduce the watering to allow the soil to dry between waterings. Underwatered plants tend to turn brown and die, while the leaves of overwatered plants tend to turn yellow. Mauʻu ʻakiʻaki is tolerant of extreme heat, drought, strong winds, and salt spray. It will grow in just about any type of soil, including sand, coralline, lava/cinder, and organic-dominant, provided there is good drainage.
Use a small amount of a balanced slow-release fertilizer with minor elements every six months or foliar feed monthly with an organic or inorganic water-soluble fertilizer at ⅓ to ½ the recommended strength to keep your plant(s) attractive and healthy. Avoid too much fertilizer since this will encourage unnaturally long leaves and pests. The flower/fruit spikes are one of the attractive features of this sedge. However, periodically trimming off these spikes seems to prolong the life of the plant. If you do trim, avoid using a string-trimmer because the trimmer cannot make clean cuts, resulting in an unattractive planting. Instead, trim or remove dead material by hand.
Pests and Diseases
Fimbristylis cymosa is infrequently attacked by sap-sucking insects such as aphids, mealybugs, scale insects, and thrips that are often protected by ants. Plants in pots stressed from prolonged drying are subject to root mealybugs or fungal infections. Refer to the Pests & Diseases page for ways to deal with each of these pests and diseases.
Uses
Ancient Hawaiian
We could not find any recorded Hawaiian uses or mo‘olelo (stories) associated with this plant.
Modern
Special Features and Information
General
The Sedge family (Cyperaceae) consists of approximately 5,500 species in about 90 genera [WikipediA;Cyperaceae]. Of the 200 to 300 species of Fimbristylis worldwide [WikipediA;Fimbristylis], three are native to Hawai‘i, with one endemic and two indigenous species.
Mauʻu ʻakiʻaki does not have the characteristic sharp-edged leaves like many other sedges. Instead, the leaves are short, stiff, and pointed, likely adaptations to reduce water loss and withstand strong coastal winds and salt spray.
Hawaiian Name
Mauʻu is a nonspecific name Hawaiians used for grasses, sedges, rushes, and some herbaceous plants. ʻAkiʻaki is the Hawaiian name for the native seashore dropseed (Sporobolus virginicus), a grass that grows on sandy beaches. It is also the Hawaiian name for a course red seaweed or limu (Ahnfeltia concinna) [Pukui & Elbert 1986].
Etymology
Fimbristylis comes from the Latin word, fimbria, meaning "thread or fringe," and the Greek word, stylos, meaning "pillar or column," likely a reference to the flower's style being bordered by long, slender processes (i.e., being fimbriate) in some members of the genus [Wagner et al. 1990]. The species name, cymosa, is Latin for "full of young sprouts" [Latin-dictionary.net]. The subspecies name, spathacea, is from the Latin word spatha, meaning "blade," and refers to the wide or open anthela (seed head or inflorescence) [Wiktionary], while umbello-capitata comes from the Latin words, umbella, meaning "parasol" [Latin-dictionary.net] and capitatus, meaning "having or forming a head" [Latin-dictionary.net], referring to the umbrella-like or knobby flower/fruit head of this subspecies.
BPK