Dwarf spikerush [Eleocharis coloradoensis (Britt.) Gilly], a perennial aquatic plant, is composed of many individual rosettes connected by rhizomes. Each rosette has needlelike culms attached to a stalk, a crown with an apical meristem, and many fibrous roots. It reproduces by achenes, subterranean tubers, and crown tubers. Dwarf spikerush achenes were harvested three times in 1 yr after the water level had been manipulated to promote flowering. The annual yield of achenes following this treatment was 79 kg per ha. Subterranean tubers began to form in September and formation was maximum in October. Individual plants grown for 1 yr developed an average of 351 tubers. Maximum density of tubers formed in hydrosoil was 7 per cm2. Longevity studies showed that the percentage germination of achenes and tubers decreased, respectively, from 48 to 32% and from 100 to 46% when stored wet at 4 C for 4 yr. Plants grown for 6 months from a single subterranean tuber, rosette, or achene spanned 150, 127, and 99 cm, respectively. The species thrived in a wide range of water qualities and on soft hydrosoils largely made up of silt, clay, and organic matter. On plants immersed in 0 to 100% sea water for 1 month, culms were injured in 30% sea water and killed in 40% sea water. Surviving plants showed some new growth after transfer to fresh water. Some tubers were incubated in diluted sea water. They germinated in solutions up to 80% sea water. Plants grown in water under different light intensities grew best at the maximum of 3,900 lux. More rosettes, culms, and inflorescences were produced with a 14-h photoperiod than 11- or 17-h photoperiod. Dwarf spikerush displaced other species by invading them when growth of the other plants was suppressed. The erect crowded culms of dwarf spikerush mechanically resisted incursion of other aquatic plants.