Salt Grass

Salt grass (Distichlis spicata) is a widespread grass native to the Americas but naturalized on other continents. It is most common in areas of moist saline or alkaline soils, and is a major component of the vegetation in the lower parts of San Elijo Ecological Reserve.

Like other salt marsh species, salt grass can grow and reproduce at salinities that would kill most other plants. The surface of each leaf is equipped with many tiny salt glands that remove excess salt from plant tissues by excreting drops of highly concentrated saltwater onto the leaf surface where it will be washed off by high tide, rain or fog.   Run a leaf between your fingers; the gritty feeling is caused by  tiny flakes and crystals of dried salt. Look closely at a leaf in the sun; the crystals sparkle like tiny diamonds.

Description ^{2,4,11,67,129}

Salt grass is a spreading perennial grass from horizontal stems (rhizomes and stolons) that produce roots and new plants along their length, much like Bermuda grass; one plant can give rise to a dense stand. Salt grass is generally low growing, less than 20 inches (50 cm) in height. Leaves  (blades) are produced alternately from the joints (nodes) of upright stems; leaves of each side lie in a single plane, giving the plant a pressed look. Leaves are four inches (10 cm) or less in length, narrow, linear narrowing to the tip, rolling inward along their length. The leaf base is a membranous sheath that wraps around the stem. Leaves lack hairs. Salt glands on both surfaces excrete drops of saline water that initially resemble heavy dew and evaporate to salt flakes and crystals that give the leaves a gritty feel and sparkly appearance.

Salt grass flowers (florets) are not common. In the Reserve, we have only observed a few plants with flowers or seeds, and these were all nursery-raised plants recently transplanted into a revegetation area. Unlike most grasses, florets are usually unisexual (although exceptions have been reported ^4,129); male and female florets occur on separate plants.  Florets are compressed front to back and up to 30 florets are tightly packed into spikelets which, in turn, are arranged into terminal inflorescences. Male flowers have three stamens with thread-like filaments. Anthers have two pollen sacs attached along the sides, giving each anther an “X” shape. Female flowers have a single, superior ovary with two styles with shaggy, pinkish stigmas.

Seeds are uncommon.⁴ Seed heads are dense and yellowish. The single seed is brown, smooth, ovoid, less than 1/16 inch (2.2 mm) long. It is initially dispersed with one floret bract (the palea) fused to the base.

Classification ^2,11,44,129

Salt grass is an herbaceous perennial monocot in the grass family (Poaceae, formerly Gramineae). The grass family is the fifth largest plant family and is considered to be the most economically important, containing such important food crops as wheat, rice, oats, corn, and sugar cane. Grass leaves elongate from the leaf base rather than the tip and this allows grasses to be repeated grazed without damaging the plant, making them excellent forage crops.^41,310

Grasses have unique terminology. They are recognized by their cylindrical stems (culms), which are generally hollow or pith-filled with solid joints (nodes). Leaves (blades) are flat, attached to alternate nodes; leaf bases wrap the stem forming the leaf sheaths.

Grass is most likely to be mistaken for sedges (Cuperaceae) or rushes (Juncaceae); This old jingle may help:³¹⁰

“Sedges have edges
and rushes are round.
Grasses have nodes
where the leaves are found.”

Grasses are wind pollinated, and this has resulted in a highly modified flower structure with unique terminology. There are no petals or sepals. The pistil and stamens are enclosed in two specialized bracts (the palea and the lemma); together these make up a grass floret. One or more floret is grouped along an axis (rachilla) forming a spikelet; beneath each spikelet are two additional bracts (glumes). Spikelets may themselves be clustered into larger assemblages. There are generally three stamens with long filaments and large anthers. The wind-born pollen is tiny. The pistil consists of a superior ovary and two plumose styles.

There are two species of Distichlis native to the United States (D. spicata and D. littoralis¹²⁹); both grow in the Reserve. They are distinguished from one another  by the vegetative growth form, by the number of spikelets in a cluster and by the number of bracts (glumes) at the base of a spikelet.²

Ecology  

Although 76% of the earth is covered by sea water, less than 2% of plant species are able to grow and reproduce where seawater is the primary source of water.⁴¹ Plants that survive in estuarine environments, including saltgrass, are among those special few. Most plants have some ability to prevent the uptake of toxic salts at their roots. This adaptation is well developed in estuarine plants. Nevertheless, exclusion alone is not sufficient and at least one other mechanism is necessary.

Salt grass has developed tiny salt glands that occur in rows along both sides of the leaf blades. In salt grass, these glands consist of two cells, a basal cell, and a hemispherical cap cell. The basal cell is surrounded by “collector cells” which contain large vacuoles. It is thought that the excess salt is transported into the collector cells and then moved by the basal cell into the cap cell and ultimately onto the leaf surface. This movement appears to be powered by expansion and contraction of paired membranes which form channels through the basal cell, a bit like the action of tiny bellows.³¹¹

The excreted salt can often be seen with the naked eye appearing as drops of liquid or as tiny crystals or flakes of salt. The salt can easily be tasted.

The high concentration of salt may help guard against herbivory.³⁴ In spite of the salt, however, salt grass is the host plant for the wandering skipper butterfly (Panoquina errans), which is one of a small group of butterflies that have a unique way of holding their wings when at rest (sometimes called folded-wing skippers). The wandering skipper is on the IUCN list of threatened species,¹⁷²primarily due to habitat loss.³⁴ The wandering skipper has been found in the Reserve.³¹³

Human Uses ^15,75

Indian tribes in California’s Kern Valley collected salt grass for its salt. During hot, dry weather, the grass was harvested and spread on mats just until the salt had crystallized, but the grass was still flexible; it was then pounded with poles to release the salt. Alternatively, in the early morning, while still damp, the growing grass was swept with switches and the damp salt scraped from the switches and formed into balls or cakes. Yokuts from the San Joaquin Valley used similar techniques. Salt was an important trade item and was used sparingly.

Salt grass appears to have been less important to our local Indians; presumably, they obtained plenty of salt from the ocean. The Kumeyaay boiled the salt grass and used the tea as a mouthwash “when the mouth was sore.”¹⁶

In recent years, salt grass has been used in the restoration of saline and alkaline wetlands where the strong root systems protect against erosion and buffer the adjacent land from pollutants carried by runoff water.⁶⁷ It is being grown in the Nature Collective nursery for use in revegetation projects in the Reserve.

Interesting Facts ^41,312

Salt is much more than a flavoring for hamburger and popcorn. It has played a vital role in the development of civilization around the world. Not only is salt a necessary component of human diet, but it is one of the earliest and most successful food preservatives. Many cities developed around inland salt deposits (Salzburg was named for its salt mines), and the salt trade stimulated the development of transportation corridors. Our word “salad” derives from the early practice of putting salt on leafy greens. Salt was so valuable that in some regions it was substituted for money. The Romans sometimes paid their legions in salt, ultimately giving rise to the word “salary” and phrases such as “worth his salt”.