Fibre optic grass (Isolepis cernua) is not really a grass. It is part of the sedge or cyperaceae family, also called tufted clubrush or low bulrush. Fibre optic grass is bright green with long, thin stems that grow from the centre of the plant. The end of each stem contains a terminal flower bud. The yellowish flower bud gives the plant a "fibre optic lamp" appearance. Native in the U.S. to the western states, the plant is hardy as a perennial only in USDA hardiness zones 8 to 11. Other zones may bring fibre optic grass indoors, or use it as an annual.
Plant or place a potted fibre optic grass plant in a location that receives a full day of sun.
Place indoor potted fibre optic plants in a shallow dish of water. Fibre optic grass needs to be moist at all times. The water at the bottom of the pot will help keep the roots moist. Water indoor and outdoor plants every day. Do not allow the soil to dry up in either location.
Divide the fibre optic plant if it grows too large for its pot or planting area. Use a sharp knife to cut the roots in half. Replant both halves in a pot of potting soil, or in the ground.
Trim the long stems of the fibre optic plant with a pair of sharp scissors, when the plant begins to look too thin. Cut straight across the green stems. The plant will grow back within a couple of weeks after a cutting.
You can acclimate a fibre optic plant to live submerged in a pond. Place it in a very shallow area of the pond. Gradually increase the water depth each day, until the water is 2 inches above the soil. Fibre optic plants do not require fertilisation. If fertilising other plants in the same container, use a all-purpose liquid fertiliser.