How to Plant & Grow Threeway Sedge (Dulichium arundinaceum)

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Threeway sedge's spikey stalks
Threeway sedges have spikes that are ½ – 1 inch long. Krzysztof Ziarnek, Kenraiz, CC BY-SA 4.0, via Wikimedia Commons

Dulichium arundinaceum is a herbaceous perennial found along streambanks, bogs, and marshes. The plant is commonly referred to as threeway sedge due to the formation of the leaves in three ranks along the stem when seen from above. It is classified under the Cyperaceae or sedge family, including over 5,500 known species commonly found in wetlands.

Dulichium is an aquatic or semi-aquatic plant native to most United States and Canada, excluding the Dakotas and Southwestern Deserts. Two main varieties are recognized with different distributions. D. arundinaceum var. arundinaceum is more commonly found, covering most of the species’ range in Northern America, especially east of the Mississippi River and Minnesota. D. arundinaceum var. boreale is more petite in appearance and is limited to Canada. 

Threeway sedge grows in erect clumps, often compared to bamboo shoots during their early phases due to their round and hollow stems. Light green, hairless, and flat leaves are arranged as spirals around the stem, with three leaves per cycle (3-ranked). The leaves are approximately 6 inches long and 1/3 inch wide and become progressively smaller towards the top of the stem. Inflorescences grow from the lateral buds as stalked spikes of ½ – 1 inch. During blooming periods at the end of summer, the slender spikelets are seen to spread apart before eventually disconnecting.

Facts, Benefits & Uses of Threeway Sedge

Field of threeway sedge plants
Threeway sedge stems are used by birds for shelter. Matt Lavin from Bozeman, Montana, USA, CC BY-SA 2.0, via Wikimedia Commons

Sedges are important species in many wetlands, supporting diverse food webs and a range of habitats. North American sedges, including the threeway sedge, have gained admiration. They are popular alternatives to the traditional lawn, promoting higher levels of biodiversity with lower maintenance and the ability to grow in shady areas. These humble plants act as natural filters, removing toxins from surrounding waters.

Because the threeway sedge’s fruits are achenes without apparent dispersal mechanisms, pollinators are crucial in their cultivation. Several small wild birds, including waterfowl, feast on the seeds and fruits of native sedges, acting as pollinators. Their leaves are grazed by various small mammals, including muskrats and rabbits.

Threeway sedges also act as valuable habitats. Birds use the stems of sedges as shelter and nesting sites. However, these incredible plants also support a diverse submerged ecosystem. By providing habitat to many micro- and macro-invertebrates, threeway sedges support a food web of larger vertebrates, including fish, amphibians, and reptiles. Also, following their decomposition, the sedges provide detritus for aquatic invertebrates. So, if you’re looking to begin an intricate and diverse ecosystem in your backyard, consider the threeway sedge.

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Threeway Sedge Fact Sheet:
Semi-aquatic herbaceous perennial
USDA 5 – 11
Full sun to partial shade
Brown, green
July to October
40 inches (1 m)
Transport the whole plant into moist soil
pH 4.6 – 7.5

Threeway Sedge Growth, Hardiness & Climate

Threeway sedge plants
Threeway sedges grow best in wetlands, such as bogs, marshes, and fens. Jill Lee / CC BY-SA 2.0

D. arundinaceum grows best in wetland conditions. This sedge is found along swamps and bottomland woodlands, shallow marshes, fens, bog, mucky sand flats, streams, sinkhole ponds, sloughs, and small lakes in the wild. Usually, their presence is indicative of a high-quality wetland.

Full to partial sun conditions and a cool, moist climate is ideal for this species. However, some ecotypes tolerate warmer temperatures, provided they receive adequate shading. Hardy to USDA zones 5 – 11, the species is highly well distributed and can survive in several conditions. Threeway sedges possess fibrous and slender-rhizomatous roots and should be cultivated in wet ground or shallow waters of 6-inch depths with substrate high in organic matter. Slightly acidic conditions are preferred; however, the plant can tolerate a pH of up to 7.5.

How to Plant Threeway Sedge

Threeway sedge is often purchased and planted as seeds. In nature, the seeds possess a built-in dormancy mechanism that prevents them from germinating during unpreferable conditions. These seeds germinate after a period of cold, moist stratification.

To naturally initiate the process, plant seeds outdoors during late fall (or early winter) and leave them to germinate over winter. Artificially inducing the seeds’ germination involves mixing seeds with equivalent (or higher) amounts of damp sand, vermiculite, or other stratification media. The media must be moist but not waterlogged. Place the seed mixture in a sterile, sealed plastic bag and store it in a refrigerator (33 – 40oF) for two months. In some cases, the seeds begin to sprout after just a month and should be planted immediately in a container with up to 4 inches of water.

Threeway sedges can also be propagated during late winter or early spring. To do this, transport whole plants into moist soil with adequate drainage.

How to Care for Threeway Sedge

In general, sedge care is minimal. To ensure the success of your threeway sedge, ensure that they’re kept in a high moisture environment. The best settings for this plant are bogs and water gardens. D. arundinaceum thrives in partial shade, so make sure you choose a spot that doesn’t get too much direct sunlight.

Threeway sedges rarely need fertilizer; however, should you feel they need it, feed the plant with a light nitrogen solution in early summer. Unlike lawns, these grasses don’t need regular mowing. Pruning is entirely optional, but if you wish to tidy up the appearance of your sedges, use a sharp blade to cut no more than 1/3 of the plants’ height. Managing threeway sedges is also easy – cut off the seed heads in early spring to stop new seeds from spreading.  

Is Threeway Sedge Invasive or Toxic?

Threeway sedges are native and non-invasive. This means they thrive when planted next to other native aquatic species.

There’s no evidence showing that this plant is toxic.  

Is Threeway Sedge Edible? Do Animals Eat it?

Information on the edibility and dietary properties of threeway sedges is limited. While the plant isn’t toxic, it’s not considered edible. However, some fauna feeds off the seeds, including Ametrodiplosis dulichii (Threeway sedge fruit midge) larvae, blue-winged teal, and dabbling ducks. Muskrats tend to feed off the lower stems of the plant.

This sedge shouldn’t be of concern to your pets.

Where to Buy Threeway Sedge & Seeds? (UK & US)

Dulichium arundinaceum can be purchased as seeds and plug plants from nurseries and garden centers across the US. Otherwise, they’re readily available as seeds on various online plant portals.

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