Alkali Heath

Alkali heath (Frankenia salina) is a low, woody perennial that grows in the salt marsh, forming clumps in the carpet of pickleweed. The small, scattered pink flowers are born on reddish stems. Close up, they are quite attractive but from a distance they vanish.

All salt-marsh plants can “drink” sea water because they have special adaptations to avoid being damaged by the salt. Alkali heath eliminates the toxic salt by excreting concentrated salt water through specialized glands. As the sun evaporates the water, crystals of salt are left on the foliage.

Description ^3,4,11,26,59

Alkali heath is a low-growing, evergreen sub-shrub, usually less than 2 feet (60 cm) in height, spreading from underground rhizomes and often forming dense mats. The thickened leaves are  oval to obovate less than 1/2 inch (1.4 cm) in length, with smooth edges rolled under. Leaves are opposite on reddish stems, sometimes appearing clustered.

Flowers occur singly in leaf axils; they are are bisexual, radially symmetrical and about 1/3″ (0.8 cm) in diameter. The five petals are pink-magenta, sometimes whitish or purple. The base of each petal extends into a long claw; these are hidden from view by the calyx, a tube of specialized leaves that encloses the bases of the petals. The calyx has five teeth and appears pleated; it may be pinkish-green in color. There are six (4-7) stamens of unequal lengths in two whirls. The anthers are maroon-purple in color, the supporting filaments usually the color of the petals. The pistil bears a style with three filamentous branches.  Flowers generally occur between April and October.¹

Seeds develop in a tubular capsule enclosed by the persistent calyx.

Classification ^2,7

Frankenia salina is a dicot angiosperm in a small genus in a one-genus family, Frankeniaceae. This family is characterized in part by the presence of salt-glands. Alkali heath is the only species of this family in the Reserve.

Ecology  

Plants of the salt marsh, including alkali heath, are “halophytes”- plants that can live  in sea water or in alkali soils – at salt concentrations that would kill most other plants.³¹ Halophytes may have one or several of adaptations for saline conditions. In the case of alkali heath, the leaves are equipped with tiny salt glands which concentrate the salt.⁹³ The desalinated water is used by the plant and the concentrated brine is released onto the leaf surface where it is washed away by rain, fog or high tides. On a warm day, the brine evaporates leaving visible crystals and white patches on the leaves.¹⁰⁰

Salt is not necessary for growth of halophytes, but the production and maintenance of adaptations such as the salt glands requires energy, which otherwise would be used for growth and reproduction. In the absence of a need for these adaptations, halophytes are outcompeted by other less salt-tolerant plants.¹⁰⁰

Human Uses  

As the Spanish common name Yerba Reuma (loosely translated as herb for colds) implies alkali heath has a medicinal use. The Kumeyaay made a tea from the entire plant that was used to treat colic.¹⁶ Also, it contains low concentrations of tannins which makes it a mild astringent effective for dysentery and congestion.^76,92

Interesting Facts  

Alkali heath is a host plant for the parasitic salt marsh dodder, Cuscuta salina.⁵⁹