Giant spikerush is perhaps the largest spikerush in Florida. It grows in the water of lake and pond margins. It is found primarily in the southern part of the state.
The erect stems of giant spikerush grow up to 4 feet tall, from thick rhizomes. The stem grows to about a half-inch in diameter. Obvious light-green lines on the stem of giant spikerush show that it is segmented. In cross-section, the segment walls may be seen. Giant spikerush has no leaves, but it does have long sheaths at the stem base. The sheaths are often tinged dark-red. The inflorescence of giant spikerush is a single, long, cylindrical spikelet at the tip of the stem. The spikelet is covered with brown, broadly rounded scales. The spikelet has up to 140 small flowers. The fruits are small, shiny nutlets. Giant spikerush grows from stout rhizomes. It may be the largest spikerush in Florida, with 4-foot stems, up to one-half inch in diameter. The stem has obvious light-green lines that show where the segment walls are. The plant has long, reddish sheaths on the stem. The single, large, cylindrical spikelet has up to 140 flowers.