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Marine Plants of The Texas Coast

Texas A&M University Press

Common Shoreline Plants of the Texas Coast

Introduction to Shoreline Plants

Along the shoreline fringe of Texas coastal marshes is a group of plants often overlooked or thought to be of little value. In reality, they are unique vascular plants that have had to adapt to a very hostile environment, most notably, one of higher salinity. Biologists regard these plants, which are located along estuarine creeks and intertidal shorelines, as some of the earth's most important, forming the foundation for the development and maintenance of highly productive natural marsh areas. Environmental conditions necessary for the formation of a marsh include protection from wave action, freshwater, sediment deposition, and shallow shorelines with very little slope or grade. Seasonally, the marsh vegetation decays on the mud along the shoreline, recycling nutrients, which forms the base of an extensive food web that culminates in estuarine and fisheries communities.

Most of the plants of salt marshes are referred to as halophytes (salt-loving plants) and have xerophytic adaptations (adapted to grow in low freshwater [dry] conditions) that allow them to tolerate salt conditions. Morphological and anatomical adaptations to these conditions include shallow root formation with rhizomes, erect stems that develop from the rhizomes, modifications in the leaf structure (thin and dry or thick and succulent), reduced size, and specialized structures (i.e., hydathodes, hydrocytes, etc.) that reduce the loss of water.

The dominant angiosperm monocots along the coastal shorelines are Distichlis spicata (salt grass), Monanthochloë littoralis (salt-flat grass), and Spartina alterniflora (smooth cordgrass). Common dicots include Batis maritima (saltwort), Borrichia frutescens (sea ox-eye daisy), Heliotropium curassavicum (seaside heliotrope), Limonium carolinianum (sea lavender), Lycium carolinianum (Carolina wolfberry),Machaeranthera phyllocephala (camphor daisy), Salicornia bigelovii (annual glasswort), S. virginica (perennial glasswort), Sesuvium portulacastrum (sea purslane), and Suaeda linearis (sea blite).

Batis is an excellent model of a fleshy, thick-leafed (succulent) halophyte that is monotypic and has small flowers that are found in conelike spikes. The plant has spreading or creeping stems that root at the tips and form extensive colonies in intertidal saline areas.

Salicornia is an example of a succulent (fleshy-thick) halophyte that is unique because it has lost the leaf blade. Photosynthetic tissue has been replaced by the wrapping of the fleshy-leaf petiole around the stem.

Spartina alterniflora, an example of a halophytic plant with a thin, dry (nonsucculent) leaf, uses modifications in the leaf structure to reduce the loss of water. The leaf has a thin cuticle (outer waxy covering), deep leaf grooves on the upper sides, and thin-walled hydathodes located at the base of the grooves. With the loss of water, the hydathodes will collapse, resulting in the curling or rolling of the leaf, and thereby reduce the leaf area exposed to the air and consequent water loss.

The major ecological roles of these plants and the marshes they form include the production of organic matter with a release of nutrients, habitat and food for animals, filtration of coastal runoff, and erosion control through soil trapping and stabilization. Tidal flats are an extremely valuable habitat and should not be forgotten during decisions concerning conservation issues. Although the gently sloping areas may appear sterile and contain little or no erect vegetation, the surface sediment and substrate are composed of a multitude of plants and animals. Cyanobacteria and certain other bacteria are capable of fixing nitrogen and are the primary source of nutrients for plants surrounding the tidal flats. When the area is inundated during high tides, nitrogen mixes into the water column and is transported into salt marshes, seagrass beds, and other wetland areas. The shallow-water flats are important nurseries for numerous species of fish, crustaceans, and other invertebrates, as well as feeding grounds for many shorebirds.

Except for freshwater ponds (dominated by Typha latifolia, cattail) located along the shorelines, most of the marsh plants found are members of a brackish type of marsh, which is normally situated landward of salt marshes. These marshes are subjected to inundation. The flooding may be both freshwater from rainfall and subsequent runoff or marine tidal inflow from extremely high tides. These transitional marshes create an ecotone where plants from both the salt marsh community and the freshwater marsh community meet and integrate. The result is a blending of two or more adjacent vegetation types and a more diverse community with an increased number of highly adaptable plants that tend to colonize such transitional areas.

The following descriptions have been prepared for individuals with some basic knowledge of plants. If you have difficulty understanding some of the terminology or identifying structures, obtain a general botany text from the library to help you learn the parts of a plant, especially the structure of the flower. Some effort may be required, but the rewards attained with this new knowledge will be significant. The more botanical knowledge you possess or obtain, the easier plant identifications will become.

Many of the halophytic plants common to a Texas salt marsh are described in this book. The distribution and zonation associated with those plants are dependent on the concentration of salt in the substrate and water regimens.

List of Shoreline Plants

The plant species are arranged alphabetically under the names of the genera to which they belong. The genera are also arranged in this manner within their respective families, and the families are likewise under the names of the classes to which they belong. The class arrangement follows Cronquist's System of Classification. Scientific nomenclature follows the Vascular Plants of Texas: A Comprehensive Checklist including Synonymy, Bibliography, and Index (1997) by Jones, Wipff, and Montgomery.

Class Magnoliopsida

AIZOACEAE Carpetweed Family

Sesuvium maritimum (Walter) Britton, Sterns & Poggenberg SEA PURSLANE
S. portulacastrum (Linnaeus) Linnaeus SEA PURSLANE
S. trianthemoides Correll SEA PURSLANE
S. verrucosum Rafinesque-Schmaltz SEA PURSLANE

APIACEAE Carrot Family

Hydrocotyle bonariensis Commerson ex Lamarck MARSH PENNYWORT
H. umbellata Linnaeus UMBRELLA PENNYWORT, PENNYWORT

ASTERACEAE Aster or Sunflower Family

Borrichia frutescens (Linnaeus) A. P. de Candolle SEA OX-EYE DAISY
Machaeranthera phyllocephala (A. P. de Candolle) Shinners [Rayjacksonia phyllocephala] CAMPHOR DAISY

BATACEAE Saltwort Family

Batis maritima Linnaeus SALTWORT

BORAGINACEAE Heliotrope Family

Heliotropium angiospermum Murray HELIOTROPE
H. curassavicum Linnaeus SEASIDE HELIOTROPE
H. racemosum Rose & Standley HELIOTROPE

BRASSICACEAE Mustard Family

Cakile geniculata (Robinson) Millspaugh SEA ROCKET
C. lanceolata (von Willdenow) O. E. Schulz SEA ROCKET

CACTACEAE Cactus Family

Opuntia engelmannii Salm-Dyck TEXAS PRICKLY PEAR
O. macrorhiza PLAINS PRICKLY PEAR
O. stricta SOUTHERN SPINELESS CACTUS

CHENOPODIACEAE Pigweed Family

Salicornia bigelovii Torry ANNUAL GLASSWORT
S. virginica Linnaeus PERENNIAL GLASSWORT
Suaeda conferta (Small) I. M. Johnston SEA BLITE
S. linearis (Elliott) Moquin-Tandon. SEA BLITE

CONVOLVULACEAE Morning-Glory Family

Ipomoea imperati (Vahl) Grisebach [I. stolonifera] FIDDLELEAF MORNING-GLORY
I. pes-caprae (Linnaeus) R. Brown GOATFOOT MORNING-GLORY
I. sagittata Poiret SALTMARSH MORNING-GLORY

GENTIANACEAE Gentian Family

Eustoma exaltatum (Linnaeus) Salisbury ex G. Don BLUEBELL GENTIAN

ONAGRACEAE Evening Primrose Family

Calylophus serrulatus (Nuttall) Raven [C. australis] EVENING PRIMROSE
Oenothera drummondii Hooker BEACH EVENING PRIMROSE

PLUMBAGINACEAE Leadwort Family

Limonium carolinianum (Walter) Britton SEA LAVENDER

PRIMULACEAE Primrose Family

Samolus ebracteatus Kunth SEABEACH PIMPERNEL

SOLANACEAE Nightshade Family

Lycium carolinianum Walter CAROLINA WOLFBERRY

TAMARICACEAE Salt Cedar Family

Tamarix aphylla (Linnaeus) Karsten SALT CEDAR
T. canariensis von Willdenow SALT CEDAR
T. chinensis de Loureiro SALT CEDAR
T. gallica C. Linnaeus SALT CEDAR
T. ramosissima von Ledebour SALT CEDAR

Class Liliopsida

CYPERACEAE Sedge Family

Bolboschoenus robustus (Pursh) Soják [Scirpus maritimus] SALTMARSH BULRUSH
Fimbristylis castanea (Michx.) Vahl SALTMARSH FIMBRISTYLIS
Rhynchospora colorata (Linnaeus) Pfeiffer WHITE-TOPPED SEDGE

POACEAE Grass Family

Distichlis spicata (Linnaeus) Greene SALT GRASS
Monanthochloë littoralis Engelmann SALT-FLAT GRASS
Spartina alterniflora Loisel SMOOTH CORDGRASS
S. patens (Ait.) Muhl. SALT MEADOW CORDGRASS
S. spartinae (K. von Trinius) E. Merrill ex A. Hitchcock GULF CORDGRASS
Sporobolus virginicus (Linnaeus) Kunth VIRGINIA DROPSEED
Uniola paniculata Linnaeus SEA OATS

TYPHACEAE Cattail Family

Typha domingensis Persoon. NARROW-LEAVED CATTAIL
T. latifolia Linnaeus COMMON CATTAIL

Key to Shoreline Plant Families

1. Plants with climbing or trailing stems: vines
..... Convolvulaceae
1. Plants not vines
..... 2
2. Plants with woody stems: trees (1)
..... 3
2. Plants scarcely woody unless near base: herbs and subshrubs
..... 4
3. Upland trees with scalelike leaves (2)
..... Tamaricaceae
3. Intertidal and subtidal trees, marine
..... see Mangrove Key
4. Plants with spines or thorns (2)
..... 5
4. Plants of water or land habitats that tend to stay moist: aquatic or marsh plants
..... 6
5. Plants succulent with leaves reduced to spines (4)
..... Cactaceae
5. Plants not succulent, with stiff, woody thorns
..... Solanaceae
6. Plants wholly submerged or only the flowers raised to the surface (4)
..... see Seagrass Key
6. Plants partly or not at all submerged
..... 7
7. Leaves apparently lacking or reduced to scales or sheaths (6)
..... 8
7. Leaves well developed
..... 11
8. Stems jointed (7)
..... 9
8. Stems not jointed
..... 10
9. Stems not fleshy (8)
..... Poaceae
9. Stems fleshy
..... Chenopodiaceae
10. Sheath usually open on only one side (8)
..... Typhaceae
10. Closed basal sheath; stem triangle in cross section
..... Cyperaceae
11. Leaves partly or all compound or dissected (7)
..... 12
11. Leaves simple, entire to toothed or whorled, not dissected
..... 13
12. Flowers umbellate (11)
..... Apiaceae
12. Flowers not umbellate
..... Brassicaceae
13. Leaves thick-fleshy; plants of brackish or salty soils (11)
..... 14
13. Leaves not thick-fleshy
..... 15
14. Flowers solitary (13)
..... Aizoaceae
14. Flowers unisexual and in spikes
..... Bataceae
15. Ovary superior (13)
..... 16
15. Ovary inferior
..... 18
16. Leaves all basal (15)
..... Plumbaginaceae
16. Leaves not all basal
..... 17
17. Flowers in unrolling spikes (16)
..... Boraginaceae
17. Flowers not in spikes; corolla violet
..... Gentianaceae
18. Flowers in involucrate heads (15)
..... Asteraceae
18. Flowers not in heads
..... 19
19. Corolla 1/8–3/8 inch (2–7 mm) long (18)
..... Primulaceae
19. Corolla much longer; petals four; stamens eight
..... Onagraceae

Plant Descriptions and Images

Class Magnoliopsida

AIZOACEAE Carpetweed Family

SESUVIUM Sea Purslane

* sess-OO-vee-um

S. maritimum (Walter) Britton, Sterns & Poggenberg

* mer-ih-TEE-mum

S. portulacastrum (Linnaeus) Linnaeus

* port-yoo-luh-KAS-trum

S. trianthemoides Correll

* try-an-them-OH-id-eez

S. verrucosum Rafinesque-Schmaltz

* ver-oo-KO-sum

Sesuvium is a thick and fleshy perennial with branched stems that grow flat and level with the ground, often forming extensive mats more than 2 feet (60 cm) in diameter. The leaves are smooth (glabrous), waxy, and up to 1-1/2 inches (5 cm) long. Flowers are solitary, pink, about 1/2 inch (1 cm) long. Sepals have a hornlike appendage. The cone- shaped fruit is about 1/4 inch (7 mm) long with black seeds that are either smooth or wrinkled and lustrous (1–1.5 mm long). The plants are commonly found in saline sand or clay along the upper edge of salt marshes that border wind-tidal flats. The seeds are eaten by waterfowl.

Key to the Species

1. Stamens five
..... 2
1. Stamens more than five
..... 3
2. Seeds smooth (1)
..... S. maritimum
2. Seeds wrinkled (rugose)
..... S. trianthemoides
3. Stems rooting at nodes; stems mostly trailing (1)
..... S. portulacastrum
3. Stems not rooting; branching stems mostly erect
..... S. verrucosum

S. maritimum. An annual plant that is distinguished from S. trianthemoides by its smooth seeds. Occasionally found on salt flats along coastal rivers. Blooms all year.

S. portulacastrum CENICILLA. A perennial with creeping stems to 6 feet (2 m) long, often forming mats. Leaves are 1 inch (3–5 cm) long, oblanceolate, and fleshy. Sepals are 1/4 inch (5–7 mm) long and lavender-purple on the inner side. A common plant found along bay and island beaches. Blooms April–December.

S. trianthemoides. Annual with prostrate or reclining stems to 16 inches (40 cm) long. Leaves are fleshy, 1/2–1-1/4 inches (1.5–3 cm) long. Tepals 1/4 inch (2–2.3 mm) long, pale lavender on the inner side. Plants are fairly frequent in brackish swales, marshes, and depressions along the coast. Blooms April–December.

S. verrucosum. Perennial with ascending or sprawling stems to 18 inches (45 cm) long, commonly forming colonies anchored by rhizomes. Leaves 1/2–1-1/2 inches (1.5–4 cm) long, oblanceolate, and fleshy. Tepals are 1/2 inch (4–9 mm) long and purple to rose-lavender on the inner side. Frequent on salty or brackish soils along the coast. Blooms March–December.

APIACEAE Carrot Family

HYDROCOTYLE Pennywort

* hi-droh-KOT-ih-lee

H. bonariensis Commerson ex Lamarck

* bo-nar-ee-EN-sis

H. umbellata Linnaeus

* um-bell-AY-tuh

Hydrocotyle has round (orbicular or peltate) leaves that are shallowly lobed. The leaves arise vertically from a lateral, creeping stem that is up to 20 inches (50 cm) long. They are attached to the center of the blade by the petiole. The flowers are light yellow to white and are found in umbels that are either simple or compound, which is the character that separates the two species. The fruit is flattened and elliptical in cross section. The plants thrive on wet, sandy soils that may be fresh (H. umbellata) to salty (H. bonariensis).

Key to the Species

1. Flowers (inflorescence) in a compound umbel
..... H. bonariensis

1. Flowers in a simple umbel
..... H. umbellata

H. bonariensis MARSH PENNYWORT. The plant is a perennial to 14 inches (35 cm) high with creeping stems, which root at the nodes and form extensive mats. The leaves are peltate or roundish, usually 1- 1/4–3 inches (3–8 cm) wide. Flowers are in compound umbels. The minute petals (1–1.5 mm long) are whitish to pale yellow. The plants are common on coastal sands in swales, depressions, marshes, and other moist grounds. Blooms March–November.

H. umbellata UMBRELLA PENNYWORT. A perennial much as described above but with leaves mostly smaller, 1/4–1-1/4 inches (1–3 cm) wide. The flowers are in simple umbels, unlike those of H. bonariensis. The plant is locally abundant on damp sands in swales, in depressions, and around ponds. The leaves are eaten mixed in salads. Blooms March–November.

ASTERACEAE Aster or Sunflower Family

Key to the Genera

1. Leaves have a smooth (entire) margin
..... Borrichia

1. Leaves have deeply toothed margins (edges)
..... Machaeranthera

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Excerpted from Marine Plants of The Texas Coast by Roy L. Lehman. Copyright © 2013 Roy L. Lehman. Excerpted by permission of Texas A&M University Press.
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