Watson’s Salt Bush
The plant featured on this cover of the Obispoensis would not generally be considered worthy of presentation to a general audience. Its flowers are tiny; its appearance mundane. It belongs to a plant family past students in Cal Poly’s Field Botany class nick named the “Uglyaceae.” It grows along the uppermost edge of coastal salt marshes and edges of coastal sand dunes. However, even though it is a salt marsh plant you probably won’t have to worry about getting your feet wet. This is because it grows where it gets inundated only by the highest of tides. It is Atriplex watsonii, or the Watson’s salt bush or Watson’s orach. The model for this plant was growing in the in the uppermost reaches of Morro Bay salt marsh.
The recognized common names are just translations of the scientific name which often happens to nondescript looking species. Watsonii is named in honor of Sereno Watson (1826-1892) who worked as a curator in the Gray Herbarium and was a student of plants of the Western United States. He was a participant in the Clarence King expedition that studied the natural history, especially geology, of California in the middle of the 19th Century. He published the Botany of the King Expedition in 1871.
Orach is derived from the Middle English common name for the plants included in this genus. Salt bush is the more contemporary common name applied to all members of this genus. This is in spite of the fact that not all of them grow in salty soils or are bushes. It is true that most members of the genus do favor or require salty or alkaline soils. The habit of this salt bush is a prostrate to mounded perennial herb. It has very thin stems, that spread out latterly, becoming mounded only in the center. At its tallest it is less than 10 inches tall. However, individual plants can grow to several feet in width.
The drawn plant is in fruit. Why show it in fruit? Well, the most obvious reason is that as this is written it is fall/winter and this is when it is in fruit. But, more important, it would be even less exciting when it is in bloom as the flowers are very tiny. Male (staminate) flowers are borne on separate plants from the the female (pistilate) plants (dioecious). The male flower clusters are located in the axils of leaves and are in the form of short, dense spikes. The plant shown is pistillate. We know this because there are clusters of small, paired bracts in the angle between stem and leaf base (axils). Bonnie has drawn one of these “bract sandwiches.” One would expect to find a dry, single-seeded fruit between the two bracts, but most of the bract pairs are empty. Like many plants that occur in difficult environments, such as salt marshes, most of their resource budget is expended on just surviving rather than on sexual reproduction. A second evolutionary consideration is that the probability of a new individual plant’s establishment in difficult environments is itself extremely low. So, why waste energy producing seeds when they will have an extremely low probability of finding an available site in which to germinate and grow.
Some may have noticed that I have not identified the family to which salt bushes belong. This is because my old taxonomy texts and the upcoming Jepson Manual are going to place it in different families. Classically, before DNA sequence data, salt bushes were placed in the goosefoot family, Chenopodiaceae. When the DNA sequence data became available, it was noted that genera of the mostly temperate zone chenopods and the mostly tropical family, Amaranthaceae, came out together. This led to some taxonomists to combine the two families into one. Since Amaranthaceae is the older name, it had “priority” over the name Chenopodiaceae. Therefore, if the two families are combined, then the Rules of Botanical Nomenclature require that Amaranthaceae be used. The classical Amaranthaceae contains only three genera in California (only one of them the very common & weedy pigweeds, Amaranthus) In contrast, the classical Chenopodiaceae loom large. It consists of at least 17 genera and many species.
Although most common in deserts, the family is found in many other habitats as well. In other words, the classical Chenopodiaceae contains many species that dominate many habitats in California, whereas the classical Amaranthaceae are minor components which most of us see only in our weedy flora.