Kingdom Plantae

Most of the estuary's plants are found in the tidal marsh communities fringing the bays and the rivers. These are basically terrestrial plants, though many tolerate some flooding. One aquatic plant of note, called eelgrass, creates a unique habitat beneath the tides that is crucial to the lives of many birds, fish and invertebrates.

Understanding how the plants differ from each other and why they live where they do makes exploring the estuary’s habitats and surrounding uplands so much more interesting. For the curious amateur naturalist, a brief plant primer covers some basics of botany. The review is intended to help clarify the forms and functions of plant groups in and around the estuary. In this context the major groups of plants are described.

Only flowering plants are listed here, since they are the most common group in the estuary.

SUBTIDAL-INTERTIDAL

Eelgrass
Zostera marina
This flowering perennial grows in sunlit subtidal or intertidal beds. It extends rhizomes, or horizontal stems with roots, through muddy or sandy sediments. From these grow shoots of several long leaves about a 1/2 inch wide. In summertime, their flowers release pollen grains to the tidal flows, which carry them to other flowers awaiting fertilization. Eelgrass also reproduces by sending out new rhizomes.

Beds and larger meadows of eelgrass anchor sediments and provide habitat for many invertebrate and fish species. Waterfowl (particularly brant geese) and grazing invertebrates feed on its leaves. It is most valuable as a food source after it dies and is decomposed bacteria and fungi. The nutrients generated by the plant become part of the detritus, a nutrient-rich mixture of decomposing plant and animal material that feeds many smaller animals of the food web.

TIDAL MARSH

Smooth Cordgrass
Spartina alterniflora
The tall, thick blades of grass growing in four- to five-foot stands at the water’s edge of a tidal marsh are saltmarsh cordgrass. Able to handle saltwater and submersion at high tide twice daily, it dominates the lower marsh.

It tolerates oxygen-depleted sediments by concentrating some of its root structure close to the ground surface where air can penetrate. It also has water-filled columns of tissue inside that diffuse oxygen from the leaves down to the roots, actually oxygenating the sediments around them.

Like many other salt tolerant plants (halophytes), cordgrass has remarkable ways of preventing dehydration. The cells of its roots have storage areas for salt, which create osmotic pressure. This pressure counteracts the natural tendency of the water inside the roots to seek equilibrium by moving toward the concentrated salt water outside the plant. It is actually enough pressure to draw water in for the plant’s survival. At the same time, cell membranes block most of the salt in that water from entering. Special glands in the leaves of the plant excrete any excess salt. This is why you can find salt crystals on cord grass leaves during the growing season.

It bears flower spikes in late summer. The seeds form a small portion of the diet of some ducks, particularly the black duck. The seaside and sharp-tailed sparrows, and to a lesser extent the Virginia rail, also feed on its seeds. Cordgrass also reproduces vegetatively by extending rhizomes, or horizontal stems, beneath the marsh sediments. These rhizomes are food for muskrat and geese during the off-season. The tough structural material of their leaves is indigestible to animals while alive. But at the end of the growing season, bacteria and fungi decompose them by secrete enzymes capable of breaking the plant’s cellulose. In this way, the food energy produced by the cordgrass through photosynthesis enters the detrital food cycle.

Sea Lavender
Limonium nashii
In early summer sea lavender looks like a bouquet of branches rising up a foot or more above a clump of leathery, spoon-shaped basal leaves. It grows in the lower and middle intertidal zones alone or in groups. This perennial depends on open space created by wrack-smothered grasses or some other disturbance to establish its seeds. It appears to be limited by the dense root-rhizome structures of the surrounding grasses. From July to September the plant blooms myriad tiny, purple flowers with a tubular shape along its branches.

Common Glasswort
Salicornia europaea
The thick, jointed branches of this green succulent maintain a supply of fresh water within storage cells. Meanwhile, they fend off osmotic pressure, which would draw water out toward the salty surroundings, by maintaining high salt concentrations in their vascular tissue. This is how the glasswort endures the lower marsh where evaporation leaves sediments very salty. This annual also depends on bare patches to seed itself, particularly at the beginning of the season before tall grasses grow up and block its light.

Geese eat the fleshy stems. Toward the end of the growing season the stems turn red, gracing the marshscape with a fall foliage display. Then ducks move in to feed on the seeds within the stem tips.

Marsh Orach
Atriplex patula
This plant with the arrowhead-shaped leaves is fairly inconspicuous amid the marsh grasses. It has been described as a fugitive since, like the glasswort and sea lavender, its seedlings are found in exposed areas not yet colonized by grasses. You can find it inshore from the stands of cordgrass, occasionally interspersed with saltmarsh hay. One of the survival strategies of this fleshy plant, favored by chewing insects like leaf beetles, is thought to be its growth within the the stands of saltmarsh hay, which beetles find less palatable. It bears clusters of green, ball-shaped flowers from July to November.

Sea Blite
Bassia hirsute
This saltmarsh succulent prefers irregularly flooded ground. It has highly branched stems with alternating green leaves that grow smaller toward the ends of the stems. Tiny, round flowers grow alone or in clusters of three toward the ends of the stems from August to October. They turn a beautiful purple color in fall.

Saltmarsh Hay, Salt Hay Grass
Spartina Patens
Unable to cope with prolonged submersion in the tides, saltmarsh hay dominates low- to mid-high marsh areas that rarely flood. The dense growths of its weak, thin stems typically fall to one side or another, creating cowlicks across the meadow. They bloom several, alternating narrow flower spikes the color of wheat at the top of their stems from late June to October. It also reproduces vegetatively, by extending its rhizomes. The plant is food for several kinds of animals (see cordgrass, above).

Spike Grass
Distichlis spicata
Spike grass is a smaller, narrow-stemmed grass with alternating green leaves found interspersed with salt hay. The stems are green, with some yellow above each sheath (base of the leaf) overlapping the stem. It quickly colonizes disturbances and other bare patches in the marsh by sending out runners, but it lacks a dense enough root system to out-compete saltmarsh hay.

From August to October spike grass bears a clump of little spikelets at the top of the stem: five on the female plant and eight to ten on the male plant.

Black Grass, Black Needle Rush
Juncus gerrardii
Looking out over some marshes in the summertime, the high marsh grasses are often speckled with dark brown. These are the tiny flowers of a small rush with only one or two narrow leaves, and a stem that is round in cross section. (“Rushes are round…”) The brown flowers bloom in a small, branched arrangement at the end of the stem. They are food for waterfowl, marsh birds and song birds.

Black grass typically grows in infrequently flooded areas, and has densely matted roots and rhizomes for surviving in the competitive upper marsh community. It is considered a dominant plant of the upper high marsh.

Salt Marsh Bulrush
Scirpus robustus
The stem of this tri-cornered perennial sedge grows to over three feet tall in the upper marsh. (“Sedges have edges…") The most obvious characteristic of this plant grows from a certain spot on the upper end of the stem from July to October: a bunch of brown spikelets flanked by long tapering grass-like leaves. A spikelet is a collection of flowers growing along an elongated axis. The bases of some spikelets attach to the stem, while others are extended on stalks. These grow into brown nutlets.

This is one of at least 40 species of bulrushes found in the US marshlands. A wide range of waterfowl, marsh birds and shorebirds consume the seeds. Muskrats and geese eat the rhizomes. In general these plants provide nesting cover for waterfowl and some marsh birds, as well as protective cover to small mammals.

Perennial Saltmarsh Aster
Aster subulatus
From August to October, this perennial adds a splash of color to the greens and browns of the high marsh with its light purple, blue or white daisy-like flowers. It stands from six to thirty-two inches tall and has narrow, green leaves. Along the upland border or the marsh, groups of them can often be found showing dozens of flowers at a time.

The annual saltmarsh aster can be found in the same places. Its smaller flower heads are purple or blue, andhave shorter rays.

Seaside Goldenrod
Solidago sempervirens
This plant typically stands in groups, three to four feet high in the upper marsh. In spring and summer its bright green, fleshy, lance-shaped leaves grow up alternately around the stem, harbingers of the coming fall show. Finally hundreds of tiny, bright yellow flowers bloom on stalks from the top of the stem from August to October. The seaside goldenrod is one of over a hundred goldenrod varieties. In general some songbirds feed on goldenrod seeds, and small mammals like rabbits and mice eat its foliage.

Purple Loosestrife
Lythrum salicaria
Here’s a common flower you have seen bordering wetlands along the highways. Up close, pairs of lance-shaped leaves sit opposite each other on a square stem, which reaches to over three feet high. From afar the dense stands of this loosestrife seem so lovely, brightening the landscape with their tall spikes of bright purple flowers

Purple loosestrife is considered by some to be a weed that is destructive to wetland habitats. It spreads aggressively, sometimes releasing more than 2.5 million seeds per flower spike each year, as well as extending root shoots. It also tolerates a wide range of physical and chemical conditions. The result is a monoculture of purple loosestrife, which excludes native plants (usually rare species) and offers little value to wildlife. For example, marsh birds like the Virginia rail, least bittern and marsh wren stear clear of it when nesting and foraging.

It was introduced from Europe in the 1800’s, in ship ballast, wool, and likely as an ornamental herb. There are no known natural predators of purple loosestrife in this country.

Poison Ivy
Toxicodendron radicans
This plant typically grows to about knee high, but can be found up to six feet tall (ten feet if climbing). Its shiny green leaves grow in groups of three from long stalks, which are arranged alternately up a woody stem. DON’T TOUCH THE LEAVES. The sap oil, most abundant in spring and summer, can cause an extremely itchy skin irritation.

From May to July poison ivy bears clusters of yellow flowers. In August the leaves turn red. Small grayish white, ball-shaped fruits are borne in clusters, until November.

Narrow-leaved Cattail
Typha angustifolia
These grow up to six feet tall in the high marsh. Their long, strap-like leaves grow straight up from the base of the plant, and sometimes bend to the side. Each plant has both male and female flowers in the form of spikes raised on a stalk at the top of the plant. It blooms from May through July.

The male spike on top becomes covered with pollen grains, and then disintegrates. When fertilized, the long, thin brown female flower forms thousands of seeds with silky bristles. In fall, its velvety outer covering turns a dark brown color and remains on the stalk through winter.

This plant is an indicator of fresh water flows. Muskrats eat the rootstocks and leaves.

Common Reed
Phragmites australis
This is another common sight in wetlands along the highway. The round hollow stems of this grass grow up to 14 feet tall, and are covered with two-foot long, tapering leaves. A long, feathery flower cluster blooms from the top from July to October. It starts out purple and turns light brown at the end of the season. The common reed tolerates fresh to brackish salinities.

This is another invasive species. It aggressively colonizes disturbed areas, creating a phragmites monoculture, which lowers the diversity of plant life, particularly in freshwater wetlands.

It reproduces mostly through seed germination, but also by extending its rhizomes underground.

Rugosa Rose
Rosa rugosa
These beautiful bloomers are a common sight on the coast, since they can tolerate salty ocean mists and poor soils. Rugosa means wrinkled, referring to their finely wrinkled, glossy green leaves with serrated edges. The branching stems of this shrub form a sprawling, six-foot shrub. The deep pink or white flowers blooming from June to October develop into bright red hips about the size of a cherry tomato. A hip is actually not a fruit, but an extension of the stem that forms a fleshy receptacle around the ovaries and styles. Throughout the summer the ovaries transform into bony seeds called achenes, and mature in late summer. Rich in vitamin C, hips can be used to make jam. They also remain on the bush into winter, providing food for deer, birds and small mammals.

Northern Bayberry
Myrica pensylvanica
The common name of this shrub refers to its bluish-gray, 1/8-inch round waxy fruits. They hold fast in small clusters along the stems even after the leaves drop in freezing temperatures. By April, tiny off-white flowers are blooming. The aromatic leaves follow, growing to four inches long. The fruit ripens in early fall, as the leaves turn red. This sea spray-tolerant shrub grows to eight feet tall, and provides shelter for songbirds. Swallows, catbirds, and to a lesser degree numerous songbirds and the Virginia rail, feed on its berries.

Copyright © 2006 Barbara Driscoll.