Wetland Vegetation

Wetland Environments
J.S. Aber and T.A. Eddy

Table of Contents
Introduction Shoreline plants
Emergent plants Floating plants
Submerged plants Vegetation zones
More plants I More plants II

Introduction

The wetland vegetation described here is grouped into four general ecological categories, depending mainly on growth position in relation to water level (Whitley et al. 1999). Of course, water levels tend to vary in wetlands on seasonal and interannual time periods according to climatic conditions and human management. While some wetland plants can tolerate substantial variations in soil moisture and water level, others have strict water requirements for survival. Thus, the following groups represent only a rough guide to typical wetland plant habitats.

  1. Shoreline: plants that grow in wet soil on raised hummocks or along the shorelines of streams, ponds, bogs, marshes, and lakes. These plants grow at or above the level of standing water; some may be rooted in shallow water.

  2. Emergent: plants that are rooted in soil that is underwater most of the time. These plants grow up through the water, so that stems, leaves and flowers emerge in air above water level.

  3. Floating: plants whose leaves mainly float on the water surface. Much of the plant body is underwater and may or may not be rooted in the substrate. Only small portions, namely flowers, rise above water level.

  4. Submerged: plants that are largely underwater with few floating or emergent leaves. Flowers may emerge (briefly) in some cases for pollination.

The following plant descriptions are based on Whitley et al. (1999), as well as other sources as noted. Ink-sketch illustrations of many typical wetland plants by Haefner (in Whitley et al. 1999) are provided in a separate handout package. All photographs below © by J.S. Aber.

Shoreline plants

Horsetails (Equistem)

Erect, segmented tubes without true leaves, up to 1.2 meters tall. Stems contain silica crystals that feel rough, like sandpaper. Used for centuries for scouring and sanding; common name "pewterwort" derived from use for scrubbing pots and pans. Common varieties in the midwest include Common Horsetail (E. arvense) and Winter Scouring Rush (E. hyemale). Growing here (dark shoots) among Western Coneflowers beside a small stream, Sangre de Cristo Mountains, southern Colorado.

Western Coneflower (Rudbeckia occidentalis Nutt.) is found in mountains of the western United States at elevations 5000 to 9000 feet. It is common in wet soils of streambanks and woodlands, particularly in aspen groves.

Buttonbush (Cephalanthus occidentalis)

Deciduous bush or small tree, that may exceed 3 meters in height, growing immediately beside lakes and streams, sinkholes and swamps. Most distinctive are the showy, white flower clusters, which are shaped like spherical pincushions. The fragrant flowers draw numerous butterflies, bees, and other insects. The seeds are eaten by waterfowl and other birds; shrub provides good cover for nesting. Buttonbush is a member of the Quinine family, and its inner bark was once used as a quinine substitute. Lake Kahola, east-central Kansas.

Purple Loosestrife (Lythrum salicaria L.)

Erect stalks growing in shrubby clusters, up to 3 meters tall. Spikes are covered with showy, purple flowers, for which it is often used as a garden ornamental. Purple loosestrife was introduced into North America from Europe in the ballast of early ships and has become an aggressive wetland weed, particularly in the northeastern United States and southeastern Canada (Freeman and Schofield 1991). It is a serious threat to native plants and is among the worst plant pests in American wetlands. Purple loosestrife has almost no value for wildlife food or shelter in the United States. Seen here with yellow flowers of the compass plant (Silphium laciniatum L.); intermittent spring, Flint Hills upland, east-central Kansas.

Mangroves

Mangroves comprise a diverse group of salt-tolerant trees that live in tropical and subtropical coastal marine environments worldwide. Their habitats depend primarily on water salinity and depth. Three species of mangroves are common in the Florida Everglades and Keys region (Stevenson 1969).

Red Mangrove (Rhizophora mangle): Lives in shallow marine water of bays and estuaries. The tree is supported by curving stilt (or prop) roots. Trees may form dense thickets that protect the coastline from storm erosion and provide cover for wildlife. The seed pod (radicle) floats to become rooted elsewhere. Tidewater, Florida Keys.

Peat Moss (Sphagnum )

Sphagnum moss includes many species that inhabit bogs and accumulate peat. For example, about 40 species are found in bogs of Finland (Laine and Vasander 1996). Through its biochemistry, Sphagnum creates highly acidic conditions that exclude most other plants, and moss is not eaten by animals. These factors allow Sphagnum to expand and accumulate peaty soil in bogs, which are particularly common in mid- to high-latitudes in North America and northern Eurasia. Moss is reddish-brown carpet in this picture from Valgasoo, southeastern Estonia. Field of view ~2 feet across.

Pine (Pinus )

Pines can live in almost any kind of habitat, including wetlands. Pine is the only tree that can survive in the acidic, nutrient-poor Sphagnum peat of raised bogs. The lack of nutrients leads to stunted, dwarf trees that grow quite slowly. These trees are 2-3 meters tall; Meenikunno Bog, southeastern Estonia.

Salt cedar (Tamarix)

Large bush or small tree, up to 4 meters tall, with attractive pink flowers. Salt cedar originated in Eurasia and was brought to North America as an ornamental shrub. During the 1930s, it was planted widely in the Great Plains and American West in windbreaks to control soil erosion. Since then, salt cedar has become an invasive plant that grows in dense thickets along streams, rivers and wetlands. It has displaced native vegetation, changed wildlife habitat, and increased fire risk. Worst of all, it consumes great quantities of ground water--a precious resource in the western U.S. Seen here near Fallon, Nevada.
Salt cedar is extremely hardy; it is quite difficult to control through conventional mechanical or chemical means. In this example, new salt cedar grows up from cut stumps at Stillwater National Wildlife Refuge, Nevada. Some biological (beetle) controls are being tested now for potential public use. For more information, see Tamarisk Coalition.

Brook Cress (Cardamine cordifolia)

Small four-petaled flowers cluster on the ends of leafy stems, up to 2 feet (60 cm) tall, in bushy clumps beside spring-fed streams and in wet meadows in montane and subalpine habitats (Dahms 1999). Also known as Bitter Cress, this plant is a member of the mustard family (Cruciferae); its flavor is stronger than watercress. Spring at head of Trinchero Creek, Culebra Range, southern Colorado.

Emergent plants

Arrowheads (Sagittaria )

Several common species, most of which are characterized by large, arrow-shaped or "sagittate" leaves, standing up to ¾ meter above water. Leaves grow in dense clusters, and some species grow large, starchy tubers at the ends of roots. These bulbs are commonly known as "duck potatoes" and are prized by both wildlife and humans. Nearly all parts of the plant are valuable as food for waterfowl, songbirds, muskrats, porcupine and beaver. Arrowheads have been introduced in wildlife refuges to improve food resources, and they are cultivated in China and Japan for human food. Squaw Creek National Wildlife Refuge, Missouri River bottomland, northwestern Missouri.

Spike Rushes (Eleocharis )

Grasslike plants that grow in clumps from 10 cm to 1½ m tall, depending on species. Characterized by leafless stems, each of which has a small fruiting spike at the top. Spike rushes are quite common in and diagnostic of wetland environments in temperate regions around the world. They provide shelter for fish, amphibians and insects, and are a food resource for many wetland birds and mammals. Pictured here is the Blunt Spike Rush (Eleocharis obtusa) growing in a shallow stream channel, southern Oklahoma.

Water Willow (Justicia americana)

Erect stems with opposed, willow-shaped leaves, for which the plant is named. Small, orchidlike, white flowers bloom on long-stemmed spikes. Roots are usually submerged in shallow water along stream or pond margins. Greatest value of water willow is for stablizing streambeds and shorelines. Lake Kahola, east-central Kansas.

Pink Smartweed (Polygonum bicorne Raf.)

Erect, climbing plant, up to 2 meters tall, with clusters of small pink flowers on a slender spike. Member of the Buckwheat Family (Polygonaceae) along with Knotweed and Buckwheat. Seen here growing in shallow water with water willow; Lake Kahola, east-central Kansas. Based on Freeman and Schofield (1991) and Zim and Martin (1950).

Prairie Cordgrass (Spartina pectinata)

Prairie cordgrass (or sloughgrass) forms a thick sod in low, wet soils. It grows up to 2 meters tall and can be cut for hay several times during the summer (Van Bruggen 1992). Prairie cordgrass tolerates high salinity levels and, so, is common in salty wetland habitats. Early spring growth in a salt marsh at Quivira National Wildlife Refuge, south-central Kansas.

Bulrushes (Scirpus )

Bulrushes, among the most beneficial emergent wetland plants, are actually members of the sedge family. They are found in all types of fresh and alkali wetland settings--marshes, river banks, and lake shorelines. They may form dense thickets along the margins of water bodies. The seeds are particularly valuable for ducks; bulrush provides nesting habitat, and it binds wet soils quite effectively. Also known as tule or club rush.

Left: Great Bulrush (Scirpus validus). Right: Alkali Bulrush (Scirpus maritimus). Stillwater National Wildlife Refuge, northwestern Nevada.

Cattails (Typha )

Among the most common wetland plants worldwide. Long, bladelike leaves and stiff flower stalks. The mature seed head looks like a brown sausage. Two varieties are common in the United States: Common Cattail (Typha latifolia), up to 2½ meters tall, and Narrow-leafed Cattail (Typha angustfolia), up to 1½ meters tall. Normally found in shallow water of pond margins and marshes, but may thrive in almost any saturated soils from roadside ditches to sinkholes.

Cattails are utilized as food (Cossack asparagus) and for weaving, candles (Candle-wick), chaulking barrels (Cooper's Reed), insulation, and many other applications. Cattails provide wildlife habitat for nesting, and the starchy root is eaten by geese and muskrats. Narrow-leafed cattail at Stillwater National Wildlife Refuge, Nevada.

Cattails are invasive and can displace more desirable wetland plants. Cattails may slow or stop the spread of other wetland plants by secreting chemicals that inhibit germination of seeds. Muskrats are an effective natural control. One or two muskrats can completely clear a pond of cattails; muskrat "eat-outs" are valuable waterfowl habitats. Kite aerial photographs, Cheyenne Bottoms, central Kansas. Left: healthy cattail beds; right: mostly dead cattails during drought of 2002-03.

Floating plants

Duckweeds (family Lemnaceae)

Numerous genera and species make up this family, which comprises the smallest and simplest of all flowering plants. They are also among the most common plants worldwide. The plant consists of a photosynthetic floating body, called a frond, and some species have tiny roots dangling below. Duckweeds are incredibly productive and are utilized as human food and feed for domestic animals. They are major food resources for birds, mammals, and fish in wetland environments. Lesser Duckweed (Lemna minor) seen here floating on top of submerged aquatic plants; near Fallon, Nevada.

Pondweeds (Potamogeton )

The pondweed genus is large and varied. All pondweeds have rooted, submerged portions, and some have floating leaves as well. Leaf form shows considerable variations from large and round to small, needlelike shapes. Underwater and floating leaves may be quite different in form on the same plant. Identification of pondweed species is difficult and requires a botanical key. Pondweeds are among the most important food plants for waterfowl in North America. Seen here in a Mined Land Wildlife Area, southeastern Kansas.

Submerged plants

Water Milfoil (Myriophyllum heterophyllum)

Stout stems with featherlike leaves that grow almost entirely underwater; stems up to 2 meters long. The long, ropelike stems drift in slow-moving water of springs and spring-fed streams. Water milfoil prefers cool, slightly alkaline water with a high calcium content (hard water), such as found in limestone terrain of the Ozarks (MO) and Arbuckle Moutains (OK). Water milfoil provides shelter and feeding areas for fish and other small animals, but it is marginal food for waterfowl. It is well suited for growth in aquaria. Seen here in a shallow spring-fed stream with watercress in the foreground. Turner Falls, Oklahoma.

Watercress (Rorippa Nasturium-aquaticum), a member of the mustard family (Cruciferae), is a succulent, long-stemmed plant growing in tangled masses or low mounds up to about 1 foot (30 cm) tall besides spring-fed streams. The leaves have a strong peppery taste; watercress is highly valued for food flavoring and medicinal uses (Tilford 1997). It is actually rich in several vitamins and minerals. Watercress absolutely requires clear, flowing water with temperature less than 18°C (65°F), which means it favors spring-fed streams.

Zonation of wetland vegetation

Wetland vegetation is typically found in distinct zones that are related mainly to water depth and salinity. As the groupings above suggest, many wetland plants have strict preferences for soil moisture and water depth. Some occupy primarily shoreline or emergent habitats; whereas others grow in floating or submerged situations. Thus, distinct zones of vegetation are developed across the transition from dry, upland positions into deep-water environments. Similar transitional zones mark the change from freshwater to saltwater chemistry along marine coastlines and around inland saline lakes and playas.

Aerial views portray distinct zones of submerged and emergent vegetation along low-energy coastline of the eastern Baltic Sea. Water in this portion of the Baltic is quite low in salinity. Kite aerial photographs, island of Vormsi, northwestern Estonia.
Männikjärve Bog, east-central Estonia. Left: overview from an observation tower. A - Sphagnum moss growing in lawns and around margins of hollows and pools, B - dwarf pines on hummocks surrounded by pools, C - conifer forest around bog periphery. Right: vertical kite aerial photograph. A = Sphagnum cuspidatum floating in water, B = S. cuspidatum around pool shore, C = S. rubellum above water, D = pine trees on hummocks along with dwarf shrubs. Elevated boardwalk is 2 feet (60 cm) wide.

Lake margin: A - water willow in shallow water, B - cattails at lake edge, C - Willow (Salix ) and other deciduous trees on wet soil. Lake Kahola, east-central Kansas.
Water willow thrives in shallow water in the foreground, and buttonbush grows from the rocky shoreline behind. Lake Kahola, east-central Kansas.
Stream margin: A - spike rush above water level, B - watercress at stream edge, C - water milfoil submerged in stream. Turner Falls, Oklahoma.
Alkali bulrush stands in shallow, brackish water in the foreground. Its taller cousin, great bulrush, forms dark green hedge behind with wet meadow in the background. Stillwater National Wildlife Refuge, Nevada.

More wetland plants I and wetland plants II.
See wetland plants of Cheyenne Bottoms.

Return to Wetland Environments syllabus.

References


© Notice: Wetland Environments is presented for the use and benefit of students enrolled at Emporia State University. Any other use of text, imagery or curriculum materials is prohibited without permission of the instructor, J.S. Aber (2014).