Cyperus alternifolius aka Umbrella Sedge

Cyperus alternifolius is a perennial sedge in the Cyperaceae family. Gardeners call it umbrella plant, umbrella palm, or umbrella sedge. It comes from sub-Saharan Africa and the Arabian Peninsula. It grows in swamps, wet grasslands, and beside streams. It has also spread beyond gardens in several world regions. Useful Tropical Plants reports its 2013 IUCN status as Least Concern.

This fast-growing plant forms clumps of upright green stems. Garden plants reach about 1.5–4 feet [0.46–1.22 metres] tall. They spread about 2–3 feet [0.61–0.91 metres] wide. Warm, wet outdoor sites can produce plants 6 feet [1.83 metres] tall. Botanical records include stems reaching 6.6 feet [2 metres]. Indoor plants stay smaller. Smooth, crowded stems rise from a strong system of roots and rhizomes. Long stems may bend over, take root, and need support.

The umbrella shape comes from narrow bracts around each stem tip. These dark green bracts look like leaves. The true leaves clasp the stems and are hard to see. Leaf blades are absent or reduced to a short upper blade. The bracts take on the leaves' role. Small flowers appear in summer and fall. They form compound umbels of spikelets above the bracts. Flower colours include green and white, while the spikelets turn brown. The flowers draw little notice beside the bold stem tops. Small brown fruits look like tiny nuts.

Grow this sedge in sun or light shade. Shield its bracts from harsh sun and strong winds. It prefers fertile soil and accepts loam or sand. Acidic to neutral soil suits it. Its roots must stay wet, including in shallow standing water. Dry roots can lead to brown leaf tips. Indoors, a pot can stand on a tray of water. Outdoors, it suits pond edges and water gardens. NC State lists USDA zones 8–11 and describes it as frost tender. Divide clumps or use stem cuttings to raise more plants.

Its upright form works as an accent in containers. Cut stems also suit fresh or dried arrangements. Stems and leaves supply material for mats, baskets, fans, and brushes. The plant can draw copper and manganese from soil. Rhizomes and self-sown seedlings can make it invasive in suitable places. NC State reports no serious pest or disease problems. Useful Tropical Plants lists no known hazards, but gives no species-specific support for eating raw stems. It records plant ash in vegetable cooking and rhizomes as a potash source. It also records traditional medicinal uses, without establishing their safety or effectiveness.