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.

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).

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.