Plant of the Week – Feb 15th 2021 – Yellow Star-of-Bethlehem, Gagea lutea (L.) Ker Gawler

Gagea lutea is a native woodland spring-flowering plant with stunningly attractive flowers, but it is rarely cultivated.

The New Flora of the British Isles (Stace, 2019) indicates the rarity of species, using R, RR and RRR. Gagea lutea is given a single R, meaning that it is uncommon nationally, found in fewer than 250 out of the 3859 10x10km grid squares or hectads since 1987.

It has a scattered distribution in Britain, being most abundant in the Yorkshire Dales and the Lake District and absent from Ireland but with few localities in our area. It is listed as scarce in the Midlothian Rare Plant Register (Sumner, 2020) and is scarce generally in Scotland except in Perthshire where there is a significant centre of population. The populations on the banks of the river Esk in the Lothians appear to have been present since at least 1946 and have been reported repeatedly since. Preston, Pearman and Dines noted in the 2002 New Atlas that Gagea is shy to flower, and because of the inconspicuous appearance of its single leaf, it may often be overlooked and thus under-recorded.

Gagea lutea is described as a bulbous geophyte, a plant with a small, yellowish bulb about 1cm in diameter, about 25cm in height.  It usually produces a single leaf from the bulb and a single round flower stem bearing about five or six flowers in an umbel-like arrangement radiating from a point and subtended by two leaf-like bracts.  The flowers are ‘perfect’ (meaning that they contain fully functional male and female organs). They have six tepals in two whorls of three, the tepals bright yellow above, grading to green at the tips and with a broad green stripe on the lower (abaxial) surface. The six stamens are yellow with orange anthers and pollen, and the superior ovary is three-parted, the three fused green styles terminating in a three-lobed yellow stigma. The basal leaf is linear lanceolate, 15 to 40cm long by up to 15mm wide, with a slightly glaucous, waxy appearance, slightly 3-ribbed with prominent veins on the back. The blade narrows abruptly distally by in rolling of the leaf margins to form a hooded tip.  Non-flowering plants are hard to spot among the leaves of snowdrops, bluebells and miscellaneous wild garlics (as demonstrated in the images below) and are easily overlooked, but the flowers are conspicuous and unlikely to be missed. 

General views of Gagea lutea plants, captured on 19 March 2015 (left) and 19 March 2017 (right). The slightly glaucous basal leaves and bracts with their hooded tips can be compared with leaves of other spring flowers such as Allium ursinum and A. paradoxum.  The striated abaxial surface of a basal leaf is displayed at right. © Chris Jeffree

Clapham, Tutin and Warburg (1981) give the flowering period as March to May, but, although I have not made any systematic phenological records, I have photographed the flowers as early as mid-February in mild winters, and I have never known them to persist beyond April. Perhaps that is a sign of winter warming.  The flowers are said to be pollinated by insects, but I have yet to witness this happening.

The seeds of Gagea lutea, dispersed during May, have elaiosomes, lipid-containing bodies which are probably ant-rewards and associated with ant-dispersal of many species of plants. (Ohkawara et al., 1997) They may be collected by ants and carried off into their underground tunnels.

Three inflorescences of Gagea lutea, showing flowers in various stages of opening and the two bracts subtending each inflorescence. Portions of the basal leaves are also visible. © Chris Jeffree

Close-up view of open flowers showing yellow anthers before anthesis (left) and after anthesis with orange pollen visible (right). 19 March 2017. © Chris Jeffree

A herbarium sheet showing specimens of Gagea lutea from the Western Himalayas  http://specimens.kew.org/herbarium/K000400118

Distribution
The main area of distribution of Gagea lutea is in central Europe, avoiding the most extreme oceanic margins in the west.  It extends east into Asia as far as the Ural mountains, but after a large disjunction reappears in the far east as scattered populations in eastern Siberia, Korea, Sakhalin, northern Japan, the Kurile Islands, and the Kamchatka peninsula. The species also occurs in the Himalayas (see herbarium image above).

It prefers moist, base-rich deciduous woodland, meadows, riverbanks and hedgerows and is one of the many British species that tend to follow watercourses, their seeds, bulbs or vegetative fragments being washed out of eroded riverbanks to establish in suitable locations downstream. It is a lowland species generally, but in the warmer parts of its range, for example in the deciduous woodlands of Italy, it may extend to higher altitudes up to about 1500m.

Gagea lutea scarcely extends into Wales, Ireland (only one site) or the west and far north of Scotland. Rose (1999) has listed Gagea lutea as an indicator of ancient woodland in East Anglia, but it is unclear how generally that might apply to other areas of Britain.

Left: the world distribution of Gagea lutea. From Den Virtuella Floran. Right: the distribution in Britain and Ireland. © Botanical Society of Britain and Ireland

What’s in a name?

Gagea lutea was originally named Ornithogalum luteum by Linnaeus in his Species Plantarum 1: 306 (1753) (see below).  Ornithogalum was placed in the family Liliaceae, formally named in 1789 by Antoine Laurent de Jussieu whose portrait accompanies that of Linnaeus on the crest of the Botanical Society of Scotland.

Public domain: Biodiversity Heritage Library. https://www.biodiversitylibrary.org/item/13829#page/318/mode/1up

In 1806, Richard Anthony Salisbury erected the genus Gagea, which he named after the English naturalist Sir Thomas Gage (1791-1820). Salisbury was an Edinburgh University alumnus whose naming of genera was widely unpopular. In 1809, the species Ornithogalum luteum was renamed Gagea lutea by John Bellenden Ker  (whose own name was originally John Gawler, alias Ker Bellenden or Bellenden Ker).  Salisbury’s genus Lloydia was once applied to the very rare Snowdon lily, Lloydia serotina which occurs in only 5 sites in Snowdonia, but all species in Lloydia have now been moved to Gagea, bringing the yellow star-of-Bethlehem and the Snowdon lily into the same genus.  In Sweden, Gagea lutea is commonly referred to as “spring onion”, and its bulbs are said by Linnaeus to be edible (Ker Gawley, 1809) (albeit at risk of a fine or custodial sentence in this country). In Italy also it is known as “cipollacio giallo-stellato” which roughly translates as yellow-star onion. Plants for a Future  gives it one star (out of five) for edibility of bulbs and leaves, raw or cooked, and comments that it is a famine food, only used in times of scarcity. It gets nil points for other uses or medicinal rating.

The supposedly “true” stars of Bethlehem were originally all placed in the Linnean genus Ornithogalum, a genus that is now placed in the family Asparagaceae (originally Liliaceae).  Stace (2019) comments “The genus has recently been split; our 4 spp. would occupy 4 different segregates (see synonyms), only O. umbellatum remaining in Ornithogalum.” His pain is all too tangible.

Star-of-Bethlehem Ornithogalum umbellatum turns up here and there on riverbanks and road verges a bit later than Gagea, in early June. It has been cultivated in Britain since 16th century, is widely grown in modern gardens from where it readily escapes either as seed or when gardeners throw out bulbs onto waste ground. Originally of southern European origin, Ornithogalums are neophytes that may be spreading up the east coast driven by climate change.

Ornithogalum umbellatum on dune slack near Gullane, 12 May 2019. © Chris Jeffree

References

Biological Records Centre and Botanical Society of Britain and Ireland. (2008) On-line Atlas of British and Irish Flora: Gagea lutea. https://www.brc.ac.uk/plantatlas/index.php?q=plant/gagea-lutea

Clapham, A.R., Tutin, T.G.  and Warburg, E.F. (1981) Excursion Flora of the British Isles. Third edition. Cambridge University Press. ISBN 0 521 23290 2  …

Den virtuella floran. http://linnaeus.nrm.se/flora/flora/mono/lilia/gagea/gagelut.html

Ker Gawler (1809) Botanical Magazine volume 30, no. 1200. https://www.biodiversitylibrary.org/page/472996#page/150/mode/1up

Ohkawara, K, Ohara, M and Higashi,S (1997) The evolution of ant-dispersal in a spring-ephemeral Corydalis ambigua (Papaveraceae): timing of seed-fall and effects of ants and ground beetles. Ecography 20: 217-223

Linné, Carl von (1753). Species Plantarum. vol. 1. Stockholm: Laurentius Salvius. p. 306

Plants for a Future https://pfaf.org/

Preston,C.D., Pearman, D.A and Dines, T.D. (2002) New Atlas of the British and Irish Flora. Oxford University Press.

Rose, F. (1999) Indicators of ancient woodland. British Wildlife p246. (pdf) 01027625.PDF (basingstoke.gov.uk)

Gagea Salisb., Annals of Botany (edited by König & Sims) 2: 555 (1806)

Samejima, J. , Tsujii, T. and Umezawa, S. (1985) Wild flowers of Hokkaido – Hokkaido University Press

Stace, C. A. (2019). New Flora of the British Isles (Fourth ed.). Middlewood Green, Suffolk, U.K.: C & M Floristics. ISBN 978-1-5272-2630-2.

Sumner, Barbara (2020) Midlothian Vice-county 83: Scarce, Rare & Extinct Vascular Plant Register (Second edition). Pdf Midlothian (bsbi.org)

© Chris Jeffree

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