Plant of the Week – 23rd August 2021 – Sea Beet (Beta vulgaris ssp. maritima)

Sea Beet is the wild ancestor of the familiar crops: beetroot, chard and mangelwurzel. The earliest records of its use by humans are the desiccated remains of seed stalks, carbonised seeds, and fragments of roots found in Denmark, dating from the late Mesolithic (5600–4000 BC).

Beta_vulgaris_-_Köhler–s_Medizinal-Pflanzen-167.jpg (476×593)
Beta vulgaris. Image by German botanist-herbalist Walther Otto Müller (1833 – 1887). From Wikipedia, Creative Commons.

Sometimes simply named as Beta maritima, Sea Beet is nowadays regarded as one of three subspecies of Beta vulgaris. The three subspecies are maritima (Sea Beet), cicla (Foliage Beet, including Spinach Beet and Swiss Chard) and vulgaris (Root Beet, including beetroot and mangelwurzel). Sea Beet is a British native plant, first recorded by botanist-herbalist Thomas Johnson in 1629 from the Isle of Sheppey of the coast of Kent, England (Pearman 2017).

Sea Beet growing against the harbour wall at Port Logan in SW Scotland, August 2021. Note the red pigmentation, glossy foliage and the sprawling habit, all typical characteristics of this subspecies. Flowers, fruits and seeds are born on long stems. Photo: John Grace

However, it is difficult to establish origins of the subspecies because of the lack of consistent names of species and the low level of recording. We need to look at evidence from herbals. Gerard’s Herbal (1633) not only gives a vivid botanical description of beets but also hints at a possible date for the introduction of a version of beetroot from ‘beyond the seas”. Here’s what he says:

“The common white Beet has great broad leaves, smooth and plain, from which rise thick crested or chamfered stalks. The flowers grow along the stalks clustering together like little stars, which being past, there succeed round and prickly seed. The root is thick, hard and great. There is likewise another sort, that was brought unto me from beyond the seas, by that courteous merchant Master Lete, the which has leaves very great, and red in colour, as is all the rest of the plant, as well root, as stalk and flowers, full of a perfect purple juice tending to redness”.

Gerard goes on to say that the seeds produce plants of ‘many and variable colours’.  The first, ‘white’ one, could have been something like manglewurzel or Sea Beet. The one brought from abroad must have been beetroot. In Gerard’s garden the species may have hybridised (hybrids are known to occur; the subspecies have the same number of chromosomes, 2n=18). The progeny could have been colours from white to red, just like the garden variety Swiss Chard today.  

Gerard’s 1633 illustrations. He called them ‘White Beet’ (left), ‘Red Beet’ (centre) and ‘Red Roman Beet’ (right). Note the Roman Beet (presumed beetroot), does not have the highly swollen root of the modern beetroot.

What is certain, is that Sea Beet is native. Its pollen has been reported in this country (Godwin 1975) in estuarine marine clay from the last interglacial period (about 120,000 years ago, called the Ipswichian Interglacial in UK, and the Eemian elsewhere). 

The genus Beta is a member of the family Amaranthaceae, which includes some familiar species and varieties: Amaranthus (in gardens, e.g. the variety called Love Lies Bleeding), Chenopodium (many are weeds of arable crops, e.g. Fat Hen), Quinoa (Chenopodium quinoa, the ‘superfood’), and Salicornia (called Marsh Samphire in Britain and often eaten with fish).

Many of the species in this family have the red pigment called betaine, originally isolated from Sea Beet. Beetroot is red, Sea Beet is green at first, tending to turn red, manglewurzels are not usually red at all. Most red pigmentation in the plant kingdom is from a broad class of compounds called anthocyanins. However, Betaine is quite a different pigment, a derivative of the amino acid glycine, and is found in many sea creatures including crustaceans and molluscs. In Beet and in marine invertebrates, the most important role of betaine is in osmoregulation. To survive in rapidly changing concentrations of salt, the cells of all these organisms must rapidly osmoregulate, otherwise water will rush in (or out) and thus inflate (or deflate) the cells causing structural and physiological damage. Betaine is a good osmoregulator as the molecule carries both a plus and a minus charge (it’s a ‘zwitterion’) and betaine does not interfere with other aspects of metabolism.

In the plant kingdom there are several mechanisms of salt tolerance (see Bartels and Kumar 2005). Beet seems to have gone a step further in the evolution of salt tolerance. It grows better when supplied with a little salt, sodium chloride. Gardeners of old knew this, and recent UK government advice to farmers gives the suggested dosage. All plants need potassium in rather large amounts, and it seems that in Beet the closely-related element sodium can perform some of the roles of potassium. This is what the UK government advised:

“Sugar beet is responsive to sodium which is recommended for all soils except Fen peats and some silt soils, which generally contain adequate sodium. Sodium can be applied as agricultural salt at 375 kg/ha. The application will not have any adverse effect on soil structure, even on soils of low structural stability”.

Beta vulagris ssp. vulgaris (Beetroot), the cultivated form with its familiar swollen root, upright compact habit. Photo: John Grace.

Stace (2019) describes Sea Beet as a much-branched sprawling perennial. However, it is often an annual plant according to Biancardi et al (2020). Other authorities say it is biennial. Wisely, the older flora of Clapham et al (1959) refrains from any comment regarding status as a perennial or annual. Most perennials with an over-wintering tap root store carbohydrates as starch or inulin, but the roots of Sea Beet simply accumulate sucrose. In Sugar Beet the concentrations are immense. A fresh root of this plant consists of 75% water, 20 % sugar and 5% ‘pulp’. Sea Beet usually has much less sugar than its sweet relative but sometimes it can be equally high.

The first commercialisation of beet as a source of sugar is attributed to the German Franz Karl Achard,. He opened his first factory in 1801 and is considered to be the father of the sugar beet industry. Although he died in bankruptcy (his factories often burnt down) others were more successful and built factories across Europe. The first successful factory in the USA was established by Mormon pioneers near Salt Lake City in 1852.

The flowers of Sea Beet are hermaphrodite, green and small, borne along lengthy stalks. They are wind-pollinated (although nectar is produced and a small amount of insect pollination may occur).  It is rather difficult to discern the detail of the flowers, even with a hand-lens. Each individual flower has five stamens and five ‘petals’, but these tiny floral units are grouped in tight bunches of 2-11 in the axils of leafy bracts. The pollen is released before the pistils (female organs) is receptive, thus ensuring outcrossing. After fertilisation the floral parts swell and fuse to form a seed ball. These seed balls, dried, are what the gardener finds in a packet of beetroot seed. Each one produces (usually) 1-4 seedlings.  

Sea Beet is native in Europe except in the north. It is almost always confined to the coast. It is not at all a common plant in Scotland, being sporadic on the west coast and absent on the east coast north of Dundee. Where it is most recorded in Scotland, in the south-west, it is never abundant. I have spotted it ‘at a distance’ from its glossy leaves in spring and its sprawling habit.

Records of Beta vulgaris ssp. maritima. On the left are records up to 2010, on the right are records from 2010 to August 2021. Data from the BSBI.

Is it declining? The BSBI records suggest that it hasn’t changed much (see the maps above). In Scotland it may have made small gains in the Western Isles and Orkney, and substantial gains on the island of Ireland (but it may have been under-recorded there until recently). It has declined around Edinburgh. Its European distribution suggests it is warmth-loving, and so we may expect it to increase in the coming decades. However, its main habitat, the foreshore, is often disturbed and under threat from development. Arthur Tansley’s 1939 book, The British Islands and their Vegetation, has it as a ‘frequent’ component of the foreshore community but would he still rate it thus? This plant community still exists despite seaside development, but the habitat is frequently dominated by annual weeds which can, surprisingly, often tolerate salinity.

Beet is touted as a health food, and tablets of betaine may be purchased on the internet. However, all green vegetables are rich in vitamins and minerals; that’s why we tell children to eat their greens. As for the tablets, I find no compelling evidence that they do anything useful. However, there are numerous research papers exploring the pharmacological properties of members of this most interesting family. And, for the future, there is the important prospect of genetic engineering to transfer the salt tolerance of Beet to other crops.


Bartels D and Kumar S (2005) Drought and salt tolerance in plants. Critical Reviews in Plant Sciences, 24:23–58.

Biancardi E, Panella LW and Mitchell McGrath J (2020) Beta maritima The origin of beets. Springer, Berlin.

Clapham AR, Tutin TG and Warburg EF (1959) Excursion Flora of the British Isles. Cambridge University `Press.

Godwin H (1975) A history of the British Flora, 2nd Edition. Cambridge University Press.

Pearman D (2017) The discovery of the native flora of Britain and Ireland. BSBI.

Stace CA (2019) New Flora of the British Isles. C&M Floristics.

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