Around 15% of the state of Wisconsin consists of wetland environments. These are locally defined as areas where water “is at, near, or above the land surface long enough to be capable of supporting aquatic or hydrophytic vegetation”. Substrates in these special habitats are waterlogged, occasionally flooded, or consistently moist. They support the needs of many water-loving plants, animals, and microbes.
Wisconsin boasts an impressive diversity of wetland flora with various growth habits and unique adaptations. These play several roles wherever they naturally occur. Rooted aquatic and emergent plants provide vertical structure, around and on which many microbes, juvenile fish, waterfowl, amphibians, and more semi-aquatic organisms may feed and grow. They support a well-balanced ecology that hinges on the presence of what is arguably nature’s most precious resource – water.
Though many of Wisconsin’s wetlands look the same to the untrained eye, natural scientists find that they each perform a different set of functions as a result of their varied plant composition, chemical components, and location relative to other biomes. The plants in these habitats are some of the most crucial biotic components – regardless of whether they are dominant or extremely rare.
Wisconsin is home to more than 200 species of wetland plants! Those listed below are simply some of the most notable native and non-native species. They represent a greater variation of aquatic and semi-aquatic adaptations.
1) Softstem bulrush (Schoenoplectus tabernaemontani)
Softstem bulrush is commonly found throughout Wisconsin’s sedge meadows, marshes, low prairies, shrub carrs, and open bogs. As an obligate wetland plant, it only occupies areas with consistently moist or frequently flooded substrates. It occurs as an emergent grass in the shallow zones (up to 3 feet deep) of freshwater features, where its root system can aid in maintaining the integrity of shorelines. A hardy plant, it can quickly recolonize previously plowed basins of farmed wetlands.
2) Curly pondweed (Potamogeton crispus)
This non-native hydrophyte has become a noxious weed in some parts of the US. A major component of many shallow, open-water plant communities in Wisconsin, its colonies may be a nuisance to recreational swimmers, boaters, and fishers in lakes, ponds, and river systems. Curly pondweed possesses pliable stems, some of which may measure up to 31 inches (79 cm) long. These bear submersed leaves with distinctly wavy margins. Due to its tolerance for pollutants, it often grows where native pondweed populations may be in decline.
3) Cinnamon fern (Osmundastrum cinnamomeum)
The sole living member of its genus, Osmundastrum, the cinnamon fern is considered a facultative upland species in Wisconsin’s wetlands. Along with skunk cabbages and speckled alders, it may dominate vernal pools and zones that experience seasonal floods before drying out. Its roots, which are set apart by their ‘osmunda fibers’, favor boggy, slightly acidic, and moist-retentive soils. Its attractive fiddleheads unfurl into sterile fronds that can measure up to 4 feet (1.2 meters) long.
4) River birch (Betula nigra)
Named for its tendency to grow along riverbanks, the river birch is a dominant species in some of Wisconsin’s floodplain forests. It grows alongside other water-loving trees, such as the swamp white oak, black willow, and green ash. Able to live for up to 75 years, this deciduous species is distinguished by the ornamental, flood-tolerant trunk of its young trees. These are coated in a pinkish-brown bark with delicate layers of papery scales. The cover provided by its canopy is valuable to nesting waterfowl and to several endemic insects.
5) Clasping-leaf pondweed (Potamogeton perfoliatus)
The clasping-leaf pondweed is a major vertical component of some of Wisconsin’s standing and flowing freshwater features. This rooted, submerged perennial sends out stems that grow up to 10 feet (3 meters) long. In deeper waters, these remain upright. When the water level drops, these may look as though they are floating on the surface, oriented towards the direction of water flow. As suggested by this species’ common name, its lance-shaped, petiole-less leaves “clasp” the stems. Their point of attachment is the base of the leaf itself.
6) Beaked spikerush (Eleocharis rostellata)
The beaked spikerush is a calcium-tolerant member of the Cyperaceae or sedge family. It is a dominant component of Wisconsin’s calcareous fens. This wetland biome is one of the rarest in all of North America because its groundwater is especially rife with minerals. These are commonly associated with cold, spring waters sourced from active springs and streams. Now listed as a threatened species in some US states, this sedge is also an ecologically beneficial plant in acid peatlands and salt marshes.
7) Purple-fringed riccia (Ricciocarpos natans)
The purple-fringed riccia is the sole extant member of its genus, Ricciocarpos. This liverwort is characterized by two morphologically distinct forms – a terrestrial type and an aquatic, floating type. Its floating form has flat, heart-shaped shoots (each one is technically called a “thallus”) which may easily be mistaken for its leaves. The edges of these are noticeably scalloped or furrowed, much like those of lichen. Beneath the floating shoots are dangling, purplish rhizoids that help the plant remain adrift on the water’s surface.
8) Canada blue-joint grass (Calamagrostis canadensis)
Apart from Canada blue-joint grass, this species goes by a wealth of common names and has several varieties with overlapping distributions. Also called marsh pinegrass, Canadian reedgrass, and Macoun’s reedgrass, it is found in Wisconsin’s wet prairies, sedge mats, and fresh meadows. This perennial grass forms creeping rhizomes which help stabilize loose and disturbed soils. Its branching stems, which grow up to 5 feet (1.5 meters) tall, produce coarse, arching leaves. These are highly palatable to wild grazers and livestock.
9) Lake sedge (Carex lacustris)
The lake sedge is a dominant component of Wisconsin’s shallow marshes. This grass-like sedge favors the shorelines of shallow freshwater bodies, where the base of its shoots can remain submerged in depths of up to 20 inches (51 cm). Its roots become well-established in a wide range of moist substrates, including silt, muck, and sedge peat. As these are capable of self-spreading via rhizome networks, they can colonize considerably large areas alongside other sedges and true grasses.
10) American water plantain (Alisma subcordatum)
The American water plantain thrives in wetland regions with still and slow-moving waters. Its root system favors muddy or waterlogged substrates. Though its well-established stands are able to tolerate brief periods of flooding, its leaves are actually prone to rotting when they are formed in the water column. As a result, its mature specimens may be wholly devoid of leaves if they are found on the margins of water features. In habitats that can keep the leaves exposed, you’ll find that they are broad and arranged in a rosette formation.
11) Coontail (Ceratophyllum demersum)
Also known as hornwort, coontail is one of the most commercially popular wetland plants. Often grown in aquariums and ornamental ponds, it has a knack for thriving in a wide range of freshwater environments. This hydrophyte may be rooted, with its shoots maintaining an upright form, or free-floating. Once its floating fragments come into contact with suitable substrates, they can set down their own roots. Its highly textural stems, which can outcompete many aquatic plants, are covered in whorls of needle-like leaves.
12) Common water milfoil (Myriophyllum sibircum)
The common water milfoil naturally occurs in many of Wisconsin’s shallow, open-water communities, especially those receiving lacustrine deposits and riverine sediments. To the untrained eye, this aquatic herb may look quite similar to coontail because it also produces whorls of feathery leaves. A closer inspection of the leaves reveals that they are further subdivided into fans of narrow leaflets. These are borne on slender, green stems that grow to more than 3 feet (0.9 meters) long in adequately deep waters.
13) American white waterlily (Nymphaea odorata)
The visually stunning American white waterlily is a dominant floating plant in some of Wisconsin’s slow-moving streams, calm ponds, lakes, marshes, and backwaters. Also called the sweet-scented water lily, its diurnal, long-lived blooms are remarkably fragrant. These heavily-petaled, floating flowers attract a wide range of pollinators. They elegantly complement the appearance of this species’ smooth, water-repellent leaves, which have an unmistakable semi-circular and notched morphology.
14) Flat-stem pondweed (Potamogeton compressus)
The flat-stem pondweed, also called the grass-wrack pondweed, is one of the most common Potamogeton species in Wisconsin’s wetlands. Distinguished by its noticeably flattened and branching stems, it favors nutrient-rich and slow-moving waters. Turbid and fully exposed waters are seldom tolerated. Moreover, the root system of this threatened hydrophyte struggles to become well-established whenever it is exposed to disturbances.
15) Lesser duckweed (Lemna minor)
Lesser duckweed is one of the smallest aquatic plants in wetland systems. This free-floating hydrophyte forms extensive, highly productive mats of its bright-green leaves. A single plant, which typically measures just a few millimeters wide, has up to just 4 leaves. Below each leaf is a suspended root that hangs into the water column and absorbs the necessary nutrients for plant growth. Due to this species’ rapid spread and capacity to bioaccumulate pollutants, it can be used as a wetland bioremediator, food substitute for livestock, and source of biofuels.
16) White water crowfoot (Ranunculus aquatilis)
The white water crowfoot favors Wisconsin’s calm streams and quiet lakes. This native perennial has two types of delicate leaves. Its submersed leaves are threadlike as they are heavily dissected into fine segments. In contrast, its floating leaves are small, flat, and have toothed margins. These are generally absent in faster-moving waters. In early summer, throes of white-petaled blooms arise on the crowfoot’s emergent floral stems.
17) Common bladderwort (Utricularia macrorhiza)
Though the common bladderwort is often dismissed as a typical aquatic plant, it is worthy of keen interest due to its unique way of acquiring nutrients. Instead of simply relying on the adaptations of its roots and leaves, it has evolved to produce bladder traps. These take up small microbes and aquatic invertebrates, fueling this species’ rapid growth and spread as a suspended, carnivorous plant! In summer, it is distinguished from other types of bladderworts by the presence of large, yellow blooms on emergent stems.
18) Watermeal (Wolffia columbiana)
This remarkably tiny, globular plant is arguably one of the smallest flowering perennials in Wisconsin. Widely distributed as a floating hydrophyte in calm lakes, ponds, marshes, and seasonal water features, it is capable of spreading quickly to produce dense mats on the water’s surface. It is often associated with other tiny floating plants, such as duckweed. Comparable to a photosynthetic speck, this plant is largely devoid of any definite leaf or root structures.
19) Elodea (Elodea canadensis)
Also known as American waterweed, elodea is a dominant submerged macrophyte in Wisconsin’s shallow to moderately deep waters. Its upright stems may form a significant amount of the productive biomass in ponds that are up to 25 feet (7.6 meters) deep. Now invasive in many parts of the world, it may spread vigorously via fragmentation. It seems to grow almost indefinitely, with some plants boasting stem lengths of 10 feet (3 meters) or more in optimal conditions.
20) Water shield (Brasenia schreberi)
Water shield is a perennial floating plant with features that resemble those of water lilies. Its peltate leaves dominate the surface of some of Wisconsin’s permanently inundated open waters. This hydrophyte’s leaves are distinguished from water lilies by the lack of a deep notch and by petioles that are connected to the center of their purplish undersides. The green leaves rarely grow to more than a few inches wide.
21) Wild celery (Vallisneria americana)
Wild celery is also commonly referred to as tapegrass or eelgrass. This ecologically important wetland plant is a food source and habitat for a wealth of aquatic and semi-aquatic animals. Though it forms colonial beds via runners, it is not known for being particularly troublesome outside of its native range. Its mats help filter nutrients from rapidly flowing waters. Their root systems stabilize the shorelines and bottom sediments of active freshwater bodies, engineering the development of a stable community structure.
22) Vasey’s pondweed (Potamogeton vaseyi)
Increasingly difficult to spot, Vasey’s pondweed is now considered an endangered species in several US states. In Wisconsin, it is a “species of special concern”. Like many other multi-habit aquatic plants, it has two types of leaves. Its submersed leaves are quite transparent, narrow, and long. Its floating leaves, which tend to be rare even on well-established colonies, are more oval-shaped and flat. As this species typically occurs in open water systems, disturbances like erosion and alterations to water quality can affect its survival.
23) Eurasian watermilfoil (Myriophyllum spicatum)
The Eurasian watermilfoil is one of the most troublesome non-native aquatic plants in the US. Its aggressive colonies are known for choking out entire freshwater systems, competing with native plants, and creating mats that compromise recreational activities. When its vertical stems are packed tightly, the feeding habits of important apex predators may be stifled. This can cause dramatic shifts in the food web structure. Biological and physical control measures have had to be implemented to minimize its spread.
24) Slender naiad (Najas flexilis)
The slender naiad or wavy water nymph is found in both shallow and deep water systems. This wetland herb possesses delicate shoots and leaves that typically remain submerged. As they struggle to thrive in the presence of pollutants and unstable conditions, these are often associated with pristine waters throughout their native range. In fact, this species is protected in parts of the world where its aquatic stands were once widespread.
Slender naiad is commonly found in patches along the lower depths of macrophyte growth in lakes and ponds. This distribution may be due to wave action, poor competition with other plants, and sedimentation.
25) Beck’s water marigold (Bidens beckii)
Beck’s water marigold is an emergent perennial herb with variable leaves. It isn’t remotely related to terrestrial marigolds (Tagetes spp.), but it does produce blooms that look quite similar to theirs. In late summer, its well-established stands are made more eye-catching by their solitary, terminal flower heads. These have golden-yellow petals and disc florets. Once they are pollinated, they develop into nutlets.
26) Yellow water lily (Nuphar variegata)
The yellow water lily is always a joy to behold in the wild. This eye-catching plant has leathery, bright-green, floating or emergent leaves that are borne on lengthy petioles. Much like its close relatives, the water lilies of the Nymphaea genus, its rhizomatous root system firmly anchors the leaves to bottom substrates.
From June to September, mature colonies of N. variegata send out emerging stems with solitary yellow blooms. Their distinctly small and scale-like petals give the flowers a cupped shape. In areas with considerably large muskrat populations, you’ll find that the scrumptious blooms may disappear in no time!
27) American lotus (Nelumbo lutea)
An emergent aquatic perennial, the American lotus is best distinguished by its large leaves and its fleshy seed pods. Generally found in the backwaters of the Mississippi River, this hardy plant is capable of forming extensive colonies. Its circular, bluish-green leaves may dominate the surface of large bodies of shallow water. Though these are naturally water-repellent, they tend to emerge out through the water’s surface instead of maintaining a floating habit.
28) Star duckweed (Lemna trisulca)
The star duckweed stands out among other taxa within the Lemna genus because its fronds typically remain submerged; they only rise to the surface once they enter their flowering or fruiting stage. Additionally, unlike other duckweeds, its paddle-shaped leaves tend to form clusters and can remain attached to one another for some time. For this reason, they may look like densely tangled or forked networks of stars – a testament to the world of wonder in Wisconsin’s waters.
