Scrubby Scorpion-vetch, Coronilla valentina

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Coronilla valentina subsp. glauca

Scrubby Scorpion-vetch (glaucous form): Coronilla valentina subsp. glauca

At the moment, our front garden is mainly yellow. It’s a very cheerful colour, signifying spring, even today when it is cold with a brisk north-westerly wind and the occasional flurry of sleet.

So far we have the yellow of Euphorbia characias and some yellow Tulips. Our cultivated Broom (Cytisus sp.) will be next, to be followed by Spanish Gorse (Genista hispanica). The other splash of yellow is paler and started to flower around Christmas time, with long pauses in colder weather. It comes from Coronilla valentina subsp. glauca, the glaucous form of Scrubby Scorpion-vetch.

Coronilla valentina (also known as Bastard Senna) is a member of the Fabaceae (the Pea family, which I used to know as the Leguminosae). It is a rather straggly shrub from the Mediterranean area: Portugal, Spain, Morocco, France, Algeria, Italy, Malta, Tunisia, Libya, Croatia (Dalmatia), Albania, Greece and Turkey. It has been grown in the British Isles as a garden plant since 1569 and has been introduced into parts of the United States and Kenya. It is hardy down to -5 to -10 degrees Celsius, so can grow quite happily in milder parts of the UK in a sunny, sheltered spot in well-drained soil. My plant is in a sunny, south facing spot.

The usual garden form is subspecies glauca, which has bluish-green foliage, as the name suggests. I first saw it growing by the south coast of the Isle of Wight in May 2016; it had probably been in flower for months but still looked good. I returned in May 2019 when it had been given a very drastic prune and wasn’t looking its best. Plants do get woody and leggy after several years and can be replaced with young plants raised from seed or semi-hardwood cuttings.

In a sheltered place, Coronilla valentina is an ideal plant to light up the end of winter. The Frustrated Gardener describes it as “glowing like a candle in the dark“. In his garden in Kent it “laughs in the face of February“. Here in Norfolk, this year’s cold snap in February slowed its flowering but caused it no obvious harm and my four year old plant is flowering more than ever. According to the RHS, it can grow to 1 metre by 1 metre (3 feet by 3 feet). My specimen is about this size but the Isle of Wight specimen was easily twice as tall in its coastal garden. Coronilla valentina doesn’t usually need much, if any pruning (RHS pruning group 1).

The pale lemon-yellow flowers are arranged in crown-like clusters (hence “Coronilla“, meaning crown). They are quite fragrant during the day. The scent reminds me slightly of Broom, but less powerful, but it has also been described as “a sweet peach fragrance“, “Deliciously fragrant, make sure you plant it where you can enjoy its lemon scent as it intensifies in the sun” and “reminiscent of daffodils“.

Hardy’s Plants call it “a veritable bee magnet“. In our garden the flowers attract the occasional bumblebee (Common Carder Bees, Bombus pascuorum) , but once the Euphorbia characias is in flower it is the main attraction for other insects such as flies and solitary bees. Nonetheless, it is still a good plant to grow if you have the right conditions.

Early Crocus, Crocus tommasinianus

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Early Crocus, Crocus tommasinianus

Early Crocus, Crocus tommasinianus

Spring is on its way at the allotment and, as usual, patches of Snowdrops, Winter Aconites and crocuses are providing patches of bright colour, with daffodils to follow soon.

The biggest patches of flowers in February and early March are the Early Crocuses, Crocus tommasinianus. I planted a few corms next to my Tayberry around fifteen years ago and every year the main clump increases in size and is supplemented with smaller outlying patches of flowers. They are usually in flower so early that their only insect visitors are Honeybees and the very first queen bumblebees to emerge from hibernation.

Bombus terrestris queen

A queen Buff-tailed Bumblebee, Bombus terrestris, visiting Crocus tommasinianus flowers. (Photo credit: Vanna Bartlett.)

Here in the British Isles, Crocus tommasinianus is the earliest species of crocus to appear in spring, giving its name of Early Crocus. (They are also known as ‘Tommies’, after their specific name.)

Crocus tommasinianus has delicate mauve to pale purple flowers with a white corolla tube. (You can see this tube in the left flower in the photograph above.) The flowers are accompanied by typical crocus leaves, dark green with a white stripe down the centre (note 1). After flowering the leaves and flowers die back and by mid spring the plant is confined to its corm, with no growth visible above ground.

Crocuses are members of the Iris family, Iridaceae. There are no native crocuses in Britain; they are all neophytes that have been planted or have escaped from cultivation.

Crocus tommasinianus has been cultivated in Britain since 1847 and was first recorded in the wild in 1963. It can be found in open deciduous woodland, in churchyards and gardens, on roadsides, in parks and in amenity grasslands (see distribution map).

Crocus tommasinianus

Naturalised Crocus tommasinianus in Norwich’s Earlham Cemetery.

Crocus tommasinianus is an excellent garden flower, especially in mass plantings. It copes well with hungry Grey Squirrels and Muntjac in our local cemetery (note 2). It grows well in lawns, which should be left uncut until the foliage has died down in mid spring.

Crocus tommasinianus can spread both vegetatively (the original corm splits into a number of “daughter” corms) and from seed. Given the chance, Early Crocuses will form a carpet of flowers. I love this generous habit but some gardeners don’t, which is why the offspring of discarded crocuses can sometimes be found on roadsides.

In the UK it will grow best in a sunny spot on well-drained soil; in the United States the Missouri Botanical Garden suggests “average, medium moisture, well-drained soils in full sun to part shade“. On sandy loam my allotment plants are in full sun but I have some naturalised in grass in the back garden in quite a shady spot. Insects are most likely to visit flowers in a sheltered sunny place.

The natural range of Crocus tommasinianus is in southern Hungary,  north-west Bulgaria, Albania and southern parts of the former Yugoslavia. The plant is named after Muzio Giuseppe Spirito de Tommasini (1794 – 1879), a botanist and politician from Trieste in Italy.

There are a few named varieties of Crocus tommasinianus. The garden designer Non Morris describes several (accompanied by lovely photographs) on her blog, The Dahlia Papers. They include: ‘Roseus’, ‘Bobbo’, ‘Barr’s Purple’ and ‘Ruby Giant’.

I am not certain whether Crocus tommasinianus is edible, so I would err on the side of caution and not eat it. The species certainly isn’t listed amongst the edible varieties Arthur Lee Jacobson describes on his website.

Crocus flowers open wide on sunny days but close up at night and on cold days. They do this by means of a differential growth in responses to temperature, known as thermonasty.

When the flowers warm up the inner sides of the tepals expand more quickly than the outer ones, causing them to open outwards. When the temperature falls, the outer sides of the tepals expand more rapidly and the flower closes up again. A temperature increase of just 0.36°C is enough to start the opening of the flowers. Tulips do this too (note 3).

Notes

Note 1 – There are some good photographs of Crocus tommasinianus on the Wildflower Finder website.

In his Flora, Clive Stace’s key covers thirteen spring-flowering species of Crocus, including C. tommasinianus. (Autumn-flowering species, such as Saffron, Crocus sativus) are mentioned separately.

The other main difference between C. tommasinianus and C. neapolitanus (Spring Crocus) and C. vernus (White Crocus) is the width of the mature leaves, 2 – 3 mm wide in C. tommasinianus and 4 – 8 mm wide in the other two species.

Note 2 – Sandy Leven (on the Scottish Rock Garden Club website) notes that Pheasants can sometimes eat the emerging flowers.  The Lawn and Landscape website says (for the United States at least) that Crocus tommasinianus flowers are pretty squirrel-proof.

Note 3 – Wikipedia’s entry on thermonasty also describes how Rhododendron leaves wilt in cold weather. In tulips and crocuses, the response will protect the flower’s pollen from rain and snow.

Geastrum britannicum (Vaulted Earthstar) – a nice find

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It’s always good to find something new, better when it is unexpected and better still in January, a month that generally comes last in “Best Month of the Year” competitions.

The surprise highlight of a walk yesterday was the Vaulted Earthstar fungus, Geastrum britannicum.

My friend Sarah and I were walking along a minor road just outside Norwich when we both noticed some Earthstars growing on soil on the verge, amongst Ivy, beneath trees. We both spotted the fungi at the same time and I took a series of photos.

Geastrum britannicum

Geastrum britannicum

I wasn’t sure which Earthstar we’d found, so when I came home I shared my pictures on Facebook with members of Norfolk Fungus Study Group. One of the group members, Jonathan Revett, identified them for me as Geastrum britannicum.

Jonathan is very familiar with the species, having found the first specimens on a roadside verge beneath pine trees in Cockley Cley in the Norfolk Brecks, in 2000. The nearest fit appeared to be the Rayed Earthstar, Geastrum quadrifidum, though they didn’t look quite right. In subsequent years, further forays elsewhere in Norfolk and in Hampshire, Powys and Shropshire found more of the unusual fungi. They consistently had small spores (3 – 3.5 micrometres), smaller than all the other British species of Earthstar (note 1).

Samples of the fungi were sent to Kew Gardens for its Mycology Collection and several years later they were looked at by a Spanish team comparing gene sequences in Geastrum, including the PhD student Juan Carlos Zamora (note 2). As a result, in 2015 the fungus was recognised as a new species, and given the name Geastrum britannicum because it had only been found in the British Isles .

When I originally wrote this in January 2021, Geastrum britannicum didn’t have an official name but three years later (February 2024) it is known as the Vaulted Earthstar.

It seems that the species is not necessarily rare, just overlooked (note 3). Specimens in other collections have been checked and the Kew database now contains records from ten different samples, the earliest taken in 1994 (note 4).

I have cycled by the site where we saw yesterday’s earthstars on many occasions without realising that I was passing hidden treasure. It pays to look more closely.

Below are some more of my photographs of Geastrum britannicum. More photos can be found online on Jonathan Revett’s Fenfungi website, in this Business Insider article (also Jonathan’s photos) and on the Nature Picture Library website (photo by Adrian Davies).

Geastrum britannicum

Geastrum britannicum

Geastrum britannicum

Notes

Note 1 – See page 9 in the Herefordshire Fungus Survey Group News Sheet No. 29, Spring 2015. The newsletter gives the background to the discovery and a useful summary of the identification characteristics:

  • Erect, grooved pointed ‘beak’ when fresh
  • Distinct halo around the beak which is surrounded by a rim
  • Sac may be coated with fine mica-like scurf
  • Sac may have a hanging collar-like shape at the bottom
  • Sac is raised on a stalk
  • 4 – 5 ERECT ‘legs’
  • Whole structure standing on a saucer of matted hyphae and debris
  • Habitat: mostly under churchyard yews, but also known under roadside oak and pine.

The news sheet also states that “It is the combination of these characters that is important. If only one or two characters are present, your find may be G. fornicatum, striatum, quadrifidum, or even berkleyii. If you think you have found G. britannicum, examination of the spores is essential as they are smaller than all other UK species.”

Jonathan Revett commented on my photos: “Key features are the arching arms and a fimbriate not beaked mouth which is delimited (halo around base of beak). They also seem to enjoy growing in churchyards often in large numbers”.

Note 2 – See “Integrative taxonomy reveals an unexpected diversity in Geastrum section Geastrum (Geastrales, Basidiomycota)“.  J.C. Zamora, F.D. Calonge, M.P. Martín. Persoonia vol. 34: pp130–165 (2015). The whole paper can be downloaded for free as a PDF (which I wish was possible more often.)

Note 3 – See “Geastrum britannicum – a surprisingly common new species in Britain“. Brian Spooner, Alick Henrici, A. Martyn Ainsworth. Field Mycology, vol. 16, issue 2, pp54 – 57 (2015).

Note 4 – From an online search of the Mycology Collection using “Geastrum britannicum” in the ‘Taxon’ field. All the samples were found growing on soil, sometimes in leaf litter, under a variety of trees.