Bolboschoenus maritimus
sea clubrush
Overview
Bolboschoenus maritimus is a robust rhizomatous sedge of brackish marshes, reaching 30-150 cm (12-59 in) tall from a network of underground rhizomes that swell into hard, rounded tubers. The stems are sharply three-angled, smooth, and leafy near the base, topped by a cluster of red-brown egg-shaped spikelets 1-2 cm (0.4-0.8 in) long. One to several leaf-like bracts stand up beside the flower cluster, often overtopping it. The leaves are flat, keeled, 2-10 mm (0.08-0.4 in) wide, and grey-green. Tubers store starch and let the plant resprout after grazing, cutting, or flooding, while the spreading rhizomes drive vigorous colonies that can dominate the ground they occupy. It grows in standing or tidal water and tolerates salinity that excludes most marsh plants. The same vigour makes it hard to contain in small water gardens, where it overruns less robust species. Top growth dies back to the rhizome over winter.
Native Range
Bolboschoenus maritimus is native across Europe, Asia, Africa, and Australia, growing in salt and brackish marshes, tidal flats, ditches, and lake margins. It ranges inland along saline and alkaline wetlands as well as coastal sites.Suggested Uses
Used in wildlife ponds, reedbed filtration, and the restoration of brackish and saline wetlands where it binds mud and shelters wildlife. Its tubers and seeds feed waterfowl. The spreading habit makes it unsuited to small ornamental ponds without containment.How to Identify
Appearance
Size & Dimensions
Height1' - 4'11"
Width/Spread2' - 4'
Colors
Bloom Information
Wind-pollinated spikelets ripen from June to August (early to late summer). The clustered red-brown spikelets shed pollen and then set hard nutlets that float and spread on water. Flower clusters persist and brown through autumn.
Detailed Descriptions
Foliage Description
grey-greenGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Bolboschoenus maritimus grows in full sun in shallow standing water or permanently wet ground, including brackish and saline soils. It tolerates water depths to about 30 cm (12 in) over the crown and a wide pH from 6.0 to 8.5. The aggressive rhizomes and tubers spread fast, so it is grown in contained beds, baskets, or lined ponds where its reach is limited. It needs no feeding in fertile mud. It is propagated by dividing rhizomes or separating tubers in spring. Cutting below the waterline weakens stands over time.Pruning
Dead stems are cut back to the waterline or base in late winter before new shoots emerge. Cutting repeatedly through summer reduces the vigour of spreading stands. Tubers and rhizomes are dug out to control spread.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
winter
Container Growing
✓ Suitable for container growing
Minimum container size: 5 gallons