Arrowgrass (Triglochin maritima) - How to Grow & Care Guide

Plant Snapshot

Common Name: Arrowgrass
Latin Name: Triglochin maritima
Hardiness Zones: Typically a cold tolerant coastal species in cool temperate climates. Local hardiness limits vary by region so confirm for your area.
Typical Height: 4–16 in (10–40 cm) tall
Typical Spread: 6–12 in (15–30 cm) across for typical clumps
Bloom Period: Summer months in temperate regions
Soil Preferences: Prefers wet to waterlogged soils and tolerates saline marsh conditions. Performs poorly in persistently dry, well drained soils.
Light Preferences: Full sun to part shade. Best performance and flowering in full sun in open marshy sites.
Toxicity: Reported toxic to livestock when consumed in quantity. Avoid grazing and feeding to livestock. Not a known common pet food but keep pets from ingesting plant material.
Propagation: By seed and by division of established clumps. Seed propagation may benefit from cold stratification and division is usually done in spring.

Key Facts

Perennial, grasslike marsh plant native to temperate and subarctic coasts of the Northern Hemisphere
Forms low clumps or mats of narrow, linear leaves
Flowers on upright spikes of small greenish to brownish flowers in summer
Prefers wet to waterlogged soils and tolerates saline conditions
Used in coastal and wetland restoration and naturalistic plantings
Propagates by seed and by division of clumps
Reported to be toxic to grazing livestock when ingested in quantity

Arrowgrass is a low perennial marsh plant with narrow linear leaves and summer flower spikes. It fits coastal and wetland plantings where soils stay wet or waterlogged and often tolerate salty conditions but performs poorly in dry garden soil.

Identification

Grasslike and perennial, Arrowgrass forms low clumps or mats of narrow leaves and reaches about 4 to 16 inches tall. In summer it produces upright spikes of small greenish to brownish flowers. The species is native to temperate and subarctic coasts across the Northern Hemisphere and presents a fine textured groundcover habit in marshy sites.

Where to Grow Arrowgrass

Plant Arrowgrass in wet to waterlogged soils where it tolerates saline marsh conditions and open exposure. It performs best in full sun to part shade and is commonly used in coastal restoration, salt marsh edges and naturalistic wetland plantings. Avoid placing it in persistently dry, well drained garden beds where plants will struggle to persist.

Planting and Spacing

Establish by planting clumps so the crown sits at the soil surface and space plants to reflect their typical spread of about 6 to 12 inches across. Division is usually done in spring to expand or renew stands. Seed propagation is possible and may benefit from cold treatment but verify recommended seed handling with a propagation source before sowing.

Watering and visible effects

Consistently wet or waterlogged soil encourages dense clump and mat formation and supports summer flowering. In drier, well drained soil plants show reduced vigor and poor flowering. In coastal sites saline tolerance lets Arrowgrass occupy habitats where many ornamentals fail, producing steady low cover when moisture is reliable.

After Flowering and Maintenance

Maintenance is minimal in naturalistic or restoration settings. Remove damaged or dead foliage and plan divisions in spring to rejuvenate crowded clumps. Because it is adapted to wet soils little supplemental irrigation is needed in its preferred habitat. Monitor stands for thinning needs if mats begin to smother nearby plants you wish to keep.

Controlling Spread and landscape use

Arrowgrass forms low mats with spread that varies by site moisture and management. Control is by periodic division, physical removal of runners and edge barriers in planted beds. It is used where a salt tolerant low groundcover is required, but avoid grazing livestock since some Triglochin species have caused poisoning when consumed in quantity.

Frequently asked questions

How fast does Arrowgrass grow?: Growth rate varies with moisture and climate. Clumps commonly reach about 6 to 12 inches across as they establish. Expect slower establishment in dry sites and more rapid matting in consistently wet, nutrient rich locations.
Is Arrowgrass toxic to animals?: Some Triglochin species contain compounds reported to cause livestock poisoning when grazed or conserved as hay. Avoid allowing livestock to graze dense stands and check veterinary sources for species specific advice.
Can Arrowgrass tolerate salt?: Yes. It tolerates saline marsh conditions and is suited to coastal wetland plantings where salt exposure is routine.
How is Arrowgrass propagated?: Propagate by division of established clumps, commonly done in spring. Seed propagation is also used and may benefit from cold stratification, so confirm treatments with propagation references before sowing.
Will Arrowgrass work as a garden groundcover?: It works well as a low groundcover in wet or waterlogged sites and in naturalistic wetland plantings. It performs poorly in dry, well drained garden soils so match site moisture before planting.