Leucojum aestivum

Taxonomy 

Leucojum aestivum (L.), Summer Snowflake, has enjoyed a stable taxononomic status, but in 1910 it was merged with L. pulchellum (Salisb.) creating two subspecies:

  • L. aestivum subsp. aestivum
  • L. aestivum subsp. pulchellum (Salisb.) Briq.

 

The name Leucojum is derived from the Greek for ‘white violet.’

Several non-UK native members of the genus were split into a new genus, Acis, recently after genetic results showed greater differences than between Leucojum and Galanthus.

Common names: Summer Snowflake; Loddon Lily (strictly only subsp. aestivum).

Chromosome No. 2n = 22 (Stace 2010) in both subspecies.

Leucojum aestivum

Photography: J.R. Crellin

Identification 

Leucojum is a genus in the Amaryllidoidae sub-family of the Liliaceae. These are bulbous plants with narrow leaves rising from the base of the plant. Flowers are solitary or in an umbel with a spathe at the base. The ovary is inferior. There is one stigma with a simple or three-lobed style. Some have a funnel-shaped corona within the tepals. Leucojum species have few or solitary flowers with all six tepals similar, hanging as a bell. Tepals are white with green or yellow patches. There is no corona. By contrast, Galanthus spp. (snowdrops) are distinguished by the inner three tepals forming a distinct bowl-shaped structure.

Differences between the two subspecies:

ssp. aestivum;

  • No. of flowers (2-)3-5(-7)
  • Tepals larger: 13-22 mm
  • Spathe (bract behind flowers on stem) wide: 7-11 mm.
  • Flower stem edges rough - stems with the two sharp edges remotely and often inconspicuously denticulate, at least in lower half (Stace 1997).
  •  

ssp. pulchellum;

  • Flowers (1-)2-4
  • Tepals smaller: 10-15 mm
  • Spathe narrow: 4-7 mm
  • Stem edges smooth (‘entire throughout’)
  • (In practical fieldwork the distinction is easily made by gently running the fingers along the stem edges.)

 

Leucojum aestivum ssp. aestivumLeucojum aestivum ssp. pulchellum

ssp. aestivum                                                 ssp. pulchellum

Photography: J.R. Crellin

Distribution 

Both sub-species may be found as escapes from cultivation but the more frequent sub-species in cultivation is L. aestivum subsp. pulchellum. L. aestivum subsp. aestivum occurs in Ireland, The United Kingdom, Netherlands, Belgium, Germany, France, Switzerland, Italy, Austria, Yugoslavia, Albania, Greece, Czech Republic, Slovakia, Hungary, Romania, Bulgaria, Ukraine (SW and the Crimea), Turkey, Iran, Georgia, Russia (the Caucasus) (Fl. Europaea). L. aestivum subsp. pulchellum is native to France (the Alps-Maritimes, Corsica), Spain (Balearic Islands), Italy (continent, Sardinia) (Fl. Europaea).

BSBI Hectad Map 

Click on the map to view full-size on the BSBI Maps Scheme website.

Leucojum aestivum

Leucojum aestivum ssp. aestivum

Leucojum aestivum ssp. pulchellum

Ecology 

L. aestivum subsp. aestivum occurs in wet meadows and Willow / Alder scrub by rivers in southern England north to Oxfordshire. L. aestivum subsp. pulchellum has become established in scattered communities (usually near water) through the British Isles from the Channel Isles north to Scotland but concentrated in the South of Britain and East Anglia. Neither is represented in the National Vegetation Classification.

Status 
  • Origin: L. aestivum subsp. aestivum is often considered native in some parts of the British Isles (Preston, Pearman & Dines 2002), but some botanists consider this to be rather dubious.
  • Rarity: neither subspecies is rare in Britain, although ssp. pulchellum appears to be rare in Ireland.
  • Threat: Leucojum aestivum is listed as ‘Least Concern’ in Cheffings & Farrell (2005), and in the New Atlas it is given a Change Index of +2.42, which shows a significant increase.
  • Conservation: The counties of Berkshire, Dorset and Co. Waterford all have Leucojum aestivum listed as an axiophyte, which means that the county recorders consider it to be indicative of good quality habitat.
Further Work 

The subspecies are often undifferentiated in records but are easy to distinguish once one has encountered each form. Recorders should be encouraged to make the distinction and to note any unusual habitat - particularly cases of long-established communities far from water. (The plant will survive well in drier condition in gardens - and can be seen at the top of a mound at Kew. It may be that water is more significant as a seed distribution medium than anything else.) The supposed origin of British plants creates a curious dilemma. If there really is a small native population centred on central southern England, then it should be considered Nationally Scarce, and of considerable conservation importance. However, the lack of any such status reveals the lack of confidence botanists feel in this assessment. A study of its nativity and, if it is to be considered native, its ecology in the wild, is urgently required. However, a non-native species that is increasing could just as easily be an axiophyte, if it tends to grow in good habitat and does not cause any harm. Such an understanding would be more sophisticated than the simplistic ‘native is good, alien is bad’ philosophy of the popular press.

Citation 
Crellin, J.R. (Date accessed). Species account: Leucojum aestivum. Botanical Society of the British Isles, www.bsbi.org.uk.

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