Eleocharis acicularis Seeds | Needle Spikerush

Categories：Grass, Grain & Ornamental Grass Seeds

Needle spikerush forming a dense carpet of thread-like green stems in shallow water — Needle Spikerush (*Eleocharis acicularis*): Cyperaceae, shallow water and wet mud worldwide.

LATIN NAME: Eleocharis acicularis

COMMON NAME: Needle Spikerush

Plant Profile

Needle spikerush is a mat-forming aquatic sedge found in shallow water and wet mud on every continent except Antarctica, growing five to twenty centimetres tall from a creeping rhizome. Its stems are thread-thin, bright green and leafless, so a patch looks like a square metre of grass that has been cropped by a very tidy mower. The flowers are tiny and borne in a single spikelet at the tip of each stem, and they are easy to miss entirely. In ponds and aquariums it spreads into a dense carpet that traps sediment and shelters small invertebrates, and it is one of the few plants that will grow in cold water and low light. It is also a useful indicator of seasonal wetlands, since it colonises mud that dries in summer.

Science & Biotechnology

Eleocharis acicularis is a cosmopolitan species complex rather than a single uniform plant, and chromosome counts from different continents range from diploid to hexaploid, with several cryptic species hidden under the name. It is a clonal plant that spreads mainly by rhizomes, and sexual reproduction matters less in established populations than in colonising new mud. The species is a cadmium and zinc accumulator, and it has been tested for phytoremediation of mine drainage and contaminated sediment, where it takes up metals into its roots and shoots. It also oxygenates the sediment through its aerenchyma, which affects the chemistry around its roots and the availability of nutrients to neighbouring plants. In aquarium literature it is sold as a foreground carpet plant, and it is one of the few that survives without added carbon dioxide.

Uses & Benefits

The plant is used in aquariums and garden ponds as a carpeting species, in wildlife ponds as cover for fry and invertebrates, and in constructed wetlands for nutrient and metal uptake. It is also planted around the margins of water gardens, where its fine texture contrasts with broader leaves. In the wild it is grazed by waterfowl, and its seed is eaten by ducks and small birds. It has no culinary or medicinal use. Because it spreads by rhizome, it can be invasive in a small pond, and it should be contained in a basket or a defined area. It tolerates being out of water for weeks at a time, which is why it survives in seasonal pools and why it is difficult to eradicate once established in a gravel filter bed.

Growing from Seed

Sow the seed on wet mud, not in water, pressing it into the surface and keeping the mud just flooded to a depth of a centimetre. Light and warmth are needed: keep at twenty to twenty-five degrees in full sun. Germination takes two to four weeks. Once the seedlings are a few centimetres tall, they can be moved into shallow water, and the water level can rise as the plants grow. Plant out into a pond basket with loam and a layer of gravel, and place it at ten to twenty centimetres depth. Divide the mats every two years to keep them vigorous. In an aquarium, provide moderate light and no additional carbon dioxide.

Our Take

A cosmopolitan aquatic sedge that carpets shallow water and cleans contaminated sediment. Small, tough, and hard to remove once planted.

Grass, Grain & Ornamental Grass Seeds