Damp or persistently waterlogged substrates can be quite tricky to work with in the garden. Wet zones have a unique set of ecological features. Some of these are favored by the root systems of moisture-loving plants. Unfortunately, if they promote anoxic conditions and pathogenic build-up, they may also quickly lead to plant rot. Typically found in rain gardens, along the base of slopes, and around water features, these substrates can be re-conditioned with the right sets of plants.
Grasses are some of the hardiest and most versatile ornamental and forage plants. These loosely include members of the Poaceae (true grasses), Cyperaceae (sedges), and Juncaceae (rushes) families. With thousands of widely distributed species, many of which occupy some of the most challenging environments for plants, it’s no surprise that many types of grasses can thrive in wet conditions.
In wetlands and coastal areas, grasses play important ecological roles. Their self-spreading and extensive root systems help keep shorelines intact by minimizing erosion rates. Their emergent shoots, stems, and leaves are a food source, habitat, and form of cover for all sorts of aquatic, semi-aquatic, and terrestrial animals. The species listed below are known for being productive in frequently flooded landscapes and water gardens.
1) Western wheatgrass (Pascopyrum smithii)
The sole member of its genus, P. smithii is a notably adaptable perennial. It is best known for its rough, bluish-green and prominently veined foliage. These are borne on shoots with distinctly reddish or purplish joints. Typically dominant wherever its large stands are found, this grass spreads via a network of tough rhizomes. These bear single or clustered stems that can grow as tall as 3 feet (91 cm) in optimal conditions.
Though western wheatgrass favors well-draining and heavy soils, it can easily tolerate substrates with poor drainage and low salinity levels. Moderate to high moisture levels, especially those facilitated by regular precipitation, encourages its rapid spread. Cold hardy and notably resistant to grazing, it is known for surviving through spring floods. Cattle are able to forage on its stands all throughout the year.
2) Beardless wildrye (Leymus triticoides)
Beardless wildrye, also commonly called alkali ryegrass and creeping wildrye, is often cultivated for soil stabilization purposes in riparian forests and wetlands. Its stands can survive prolonged floods, during which the stems may have a more horizontal orientation as they lay on the water’s surface. It tends to dominate meadows with poorly-drained and saline substrates. It favors zones with high alkalinity conditions and partial shade.
Colonies of beardless wildrye can survive for many years if their rhizome networks are well-established. Productive in fertile soils, this cool-season perennial produces blue-green leaf blades that progressively become more rolled within the first year of growth. These are borne on smooth stems with double spikelets along each node.
3) Reed canary grass (Phalaris arundinacea)
There is some contention as to whether or not reed canary grass is a North American native. It does have naturalized stands in the continent, though these appear to be composed of cultivars from introduced varieties. Regardless, this ornamental bunchgrass is now fairly widespread throughout wetland regions. It occasionally forms single-species stands along the shorelines of major freshwater systems in the US.
Reed canary grass can be difficult to accurately identify as its morphology is variable. In optimal environments, especially those with swampy soils, its stems may grow to a full height of about 6.6 feet (2 meters). These possess flat, hairless leaf blades, some of which may be variegated. Sod-forming, its extensive root systems are excellent for erosion control in wet areas.
4) Meadow fescue (Festuca pratensis)
In spite of its aggressive nature, meadow fescue has intentionally been planted in many parts of the US as a natural form of erosion control. Valuable as a forage grass and source of hay, it favors conditions in abandoned fields, disturbed meadows, riverbanks in urban areas, and polluted sidewalks. It can quickly invade moist lawns and outgrow less aggressive native grasses.
It can be challenging to identify this common grass because its many cultivars have subtly varied leaf widths, color patterns, and maximum heights. Meadow fescue is tuft-forming and has leaf blades that arise alternately along the length of its culms. Morphologically, it is quite similar to tall fescue (F. arundinacea), which is another Eurasian species that has become naturalized in North America.
5) Switchgrass (Panicum virgatum)
A warm-season perennial, P. virgatum is a type of bunchgrass that dominates tallgrass prairies. Often grown as a forage crop and ornamental grass, it has shown remarkable potential as a plant for soil bioremediation and carbon dioxide sequestration. In fact, it has been highlighted as an energy crop for the sustainable production of biofuel. Highly evolved, many of its ecotypes are remarkably productive.
Though well-established stands of switchgrass are able to tolerate droughts, this species grows best in deep soils with access to an abundance of rainfall and supplemented irrigation. If water is scarce, it may fail to produce favorable yields throughout its growth season. Long-lived in areas with ample moisture, it boasts highly textural and crowded shoots measuring up to 5 feet (1.5 meters) tall. Its roots readily elongate and produce vigorous rhizomes.
6) Red top (Agrostis gigantea)
Also called carpet bentgrass and black bent, “red top” is often grown for revegetation purposes, as a form of erosion control, as forage that remains green all through summer, and as a source of hay. If it is well-maintained, it is also promising as a winter lawn grass in golf courses and manicured landscapes. When left to grow to its full size, this sod-forming grass is set apart by stems that measure up to 4 feet (1.2 meters) tall. These produce narrow leaf blades.
As suggested by its common name, red top produces reddish, branching inflorescences from June to August. Its dense, naturalized stands can be found in wet meadows and along stream banks. It also favors riparian environments, where it thrives alongside other water-loving grasses and trees. Cool and moist conditions, particularly in areas with clay to loamy substrates, encourage its quick establishment.
7) Creeping foxtail (Alopecurus arundinaceus)
As creeping foxtail can rapidly spread via its aggressive rhizomes and seeds (both waterborne and windborne), it is often used to revegetate damaged landscapes. Unfortunately, its tendency to become invasive can lead to management difficulties – especially in moist areas and waterways. Its root system favors wetlands and damp grasslands, including those with markedly high nitrogen concentrations. For this reason, it shows promise as a filter crop for sewage treatment.
This member of the Poaceae family is named for the appearance of its cylindrical inflorescences. These spikes, which may measure up to 4 inches (10 cm) long, look uncannily like the tails of fox pups. These rise high above flat, cauline leaves, which are suitable for pasturelands because they last through the warmest months.
8) Palm sedge (Carex muskingumensis)
Unlike many of the aggressive, water-loving grasses listed above, the palm sedge is more partial to environments with healthy, native vegetation and fairly pristine conditions. Though it is capable of spreading via rhizomes, it does so at a slow and easily manageable pace. If you’re in search of a perennial sedge for the edges of a water garden or wildlife pond, this may be a more suitable option as it is less likely to compete with other emergent plants.
Though the palm sedge can grow away from the edges of a water feature, its soil must not be allowed to dry out. In flood plains with partial to full sun exposure, its upright stems can grow up to 3 feet (91 cm) tall. The highly textural leaves radiate outward from the stems, so they may be likened to miniature palms. If temperatures are cool enough in fall, these turn into a pretty shade of copper brown.
9) Feather reed grass (Calamagrostis x acutiflora)
‘Karl Foerster’ is an immensely popular cultivar of this naturally occurring hybrid between C. arundinacea and C. epigejos. A recipient of the RHS Award of Garden Merit, it is often grown as an ornamental plant because its feathery inflorescences can dramatically change the color of the landscape. Low-maintenance and versatile, its bright green leaf blades may last through the year in mild climates. In northern temperate zones, these turn brown prior to dying back.
In zones that are away from water features, feather reed grass will require supplementary irrigation at least 1 – 2 times per week. Its mature stands can persist through brief droughts, but do note that prolonged soil dryness can cause stunted growth. Even moisture is key to enhancing the robustness and visual appeal of this versatile grass.
10) Prairie cordgrass (Sporobolus michauxianus)
Prairie cordgrass is typically found in low-lying landscapes with persistently moist conditions. Its dense stands naturally occur close to creeks and ponds. An important border grass for water features with unstable shorelines or significantly fluctuating depths, its sod-forming root system aids in keeping the substrate intact. As it provides cover to wildlife and can serve as a source of nutrients for foragers, it is often used to restore damaged wetlands.
Also called sloughgrass, marsh grass, and rip gut, this perennial produces flowering stems that may grow up to 7 feet (2.1 meters) tall. A close inspection of its leaf blades reveals that their margins are finely toothed. The leaves maintain a width of just ¼ to ½ an inch. Though these are flat in abundantly irrigated areas, they may roll inward during the driest months of the year.
11) Indian grass (Sorghastrum nutans)
This perennial tall grass, which forms thickets that may measure up to 7 feet (2.1 meters) tall, is a prominent feature of prairies throughout south-central and southeastern states. Its lengthy leaves, which may grow to about 3 feet (91 cm) long, are bluish-green and broad. At their site of attachment to stems, their sheaths are distinguished by a ligule or outgrowth called a “rifle-sight”. From summer to fall, the leaf blades are complemented by throes of golden-brown panicles.
This showy perennial is well-adapted to deep, moisture-retentive soils. Its vigorous root system can gradually expand to densely occupy wildflower meadows. As it is a warm-season grass, it grows rapidly through the hottest periods of the year. Highlighted as an important species for habitat renewal, it tends to regrow quickly after controlled fires (i.e. for the maintenance of prairie ecosystems).
12) Big bluestem (Andropogon gerardii)
This perennial bunchgrass is named for its attractive, blue-green leaf blades and its capacity to grow big – up to 10 feet (3 meters) tall, in fact! Dense tufts of individual specimens may look like miniature hills in extensive landscapes. Amazingly, the length of their roots can rival that of their aerial parts. Determined to access more nutrients and moisture, the roots can work their way through deep layers of substrate.
Big bluestem is often used as a form of forage in pastures and agricultural zones. Its tall clumps make for excellent wildlife habitats as they are able to provide cover for many nesting prairie birds, reptiles, and herbivorous mammals. Its tough rhizomes form sods which greatly minimize erosion rates. In occasionally flooded areas, the roots can tolerate submersion for up to two weeks at a time.
13) Soft-stem bulrush (Schoenoplectus tabernaemontani)
The soft-stem bulrush takes the cake for being one of the most water-loving types of grasses. It thrives best as an emergent aquatic plant and is able to produce dense colonies in marshes, ponds, streams, and along the shorelines of larger water features. Its natural stands are partial to wetlands with poor drainage and slightly saline conditions. Once their root systems are well-established, they can survive through periodic floods.
This notable member of the sedge family (Cyperaceae) can grow to an impressive height of about 10 feet (3 meters). Its leaves are present as sheaths that wrap tightly around the base of its triangular stems. Able to bloom all throughout the year in mild to warm climates, its inflorescences are terminal, golden-brown spikelets.
14) Frank’s sedge (Carex frankii)
Frank’s sedge is typically found around rivers and ponds, in floodplains, roadside ditches, throughout sedge meadows, and in prairies. This sedge is able to thrive in both pristine and disturbed environments with ample moisture. It is especially abundant in shade, where substrates tend to remain moist for longer. Well-established specimens can survive harsh floods.
Perfect for rain gardens, Frank’s sedge grows to an easily manageable height of just 1 – 2 feet (30 – 61 cm). Though its root system can spread and self-propagate via short rhizomes, it is not known for being particularly aggressive or competitive with other native wetland plants. For this reason, it is an ideal choice for attracting wildlife and for naturalizing water gardens.
15) Orchard grass (Dactylis glomerata)
Though orchard grass is not native to North America, it has been cultivated in the continent’s high-rainfall regions for centuries. Economically important as a source of hay and as a pasture grass, its production generates millions of dollars in annual revenue. This cool-season perennial requires abundant moisture to thrive. Though it sports an extensive fibrous root system, it does not possess rhizome networks. Instead, it increases its spread by forming tillers along the base of mature stems.
Orchard grass is best distinguished by its inflorescences, which are composed of tiny spikelets of florets. Each of these spikelets may resemble the appearance of a rabbit’s foot. The leaf blades, which gradually become more flat and coarse, are V-shaped along the base. These are borne on stems that grow up to about 3.5 feet (1.1 meters) tall. Livestock and deer especially love consuming this grass. Fortunately, its shoots can withstand heavy grazing.
