Molinia caerulea var. viridiflora Lajeune - a variety of Purple Moor-grass in Suffolk

MOLIN/A CAERULEA VAR. VIRIDIFLORA LEJEUNE A VARIETY OF PURPLE MOOR-GRASS IN SUFFOLK

P. J. 0.

TRIST

The infraspecific classification of Molinia is considered difficult and necessitates its study in a wide range of environments. In Trist (1979) I recorded M . caerulea var. subspicata from Cavenham Heath ; I now find it can no longer be substantiated. M. caerulea var. arundinacea and M. litoralis are now recognised as one and the same taxon under subsp. altissima (Sell & Trist , 1988) .

Hind (1889) reported two species in addition to M . caerulea; M . depauperata (which is now considered a mountain variant of M . caerulea) and M . major (now recognised as M. caerulea subsp. altissima).

Conert (1961) recognised 12 varieties and of these , Swann (1975) recorded eight varieties in Norfolk v.cc.27 & 28 which includes three records of var. viridiftora in v .c. 28. I later list seven sites in Suffolk and I am aware of more suitable habitats . This variety is not uncommon but it is a grass which is specific to a particular habitat. This was recognised by an eminent Cambridge botanist almost 100 years ago. A Mr. F. Long collected a specimen from Upland Wood , near Norwich in 1912: he labelled the sheet 'Molinia caerulea var? ' and sent it to the Rev. E. S. Marshall in Cambridge for his opinion . His reply was that 'it is easy to make varieties out of shade grown plants: but I do not believe in them '. This sheet is in CGE and in the same folder as a sheet deposited by Marshall of a collection he made from 'a swampy thicket', Oak mere , Cheshire , v.c. 58, 1914 and labelled M . caerulea var. viridiftora!

Distribution of var. viridiflora in Suffolk

v.c. 25: Old Fen, Thelnetham , 62/017.790 , 1987, P. J. 0. Trist. Woodland above Church Farm marshes , Benacre, 62/522.833, 1958, PJOT. v.c. 26: Pashford Poors Fen , Lakenheath , 521734.835 , 1976, PJOT. Hurst Fen , Holywell Row , 52/723 .767, 1989, PJOT. Tuddenham Heath by SE cornerofRopers Heath , 521748.726, 1987, PJOT. Cavenham Heath adjacent to Ropers Heath , 521751.727, 1976, PJOT. N. ofEriswell Hall , Eriswell , 52/721.808, 1976, PJOT. Field recognition M . caerulea is recognised by its height , length of panicle and its green lemmas. The colour of grass spikelets is a variable condition and influenced by soil and environment. Considering its habitat requirements and that seed breeds true (see later) , it is considered that this taxon is best treated as a variety .

In comparison with var. caerulea, its height range of 40-85cm not only shows it to be taller but its lower height of 40cm is probably above the average height of most var. caerulea. The range of panicle length of var. caerulea 1-30cm and var. viridiftora 8-35cm do not show a significant difference , but Trans. Suffolk Nat. Soc. 26 (1990)

A VARIETY OF PURPLE MOOR-GRASS IN SUFFOLK

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in a sample of var. viridifiora panicles all will be drooping and have longer branches and longer node intervals.

Description of M. caerulea var. viridillora A compact , firmly rooted perennial forming a close tussock with strong roots up to 30cm long x 0·7- 1·2mm . Culms erect , smooth , 40-85 (-lOO)cm high , 1-noded near the base. Panicles 8-32(-35)cm long , drooping, with lateral inflorescence branches 1·5-7·5(- 9)cm long and nodes well spaced on the rhachis. Leaves 12-38(-47)cm x 2-6·5(- 8)mm, deciduous , tapering gradually to a long point, upper surface with unevenly spaced ribs and long white hairs . Sheaths rounded and smooth , culminating in a Iigule of a fringe of hairs above and below the margin of the leaf base. Lower sheaths fibrous , later breaking down into strands: scales around basal club-shaped internode 3·5- 6cm long.

Spikelets (3·3-)4-5·5(-6)mm long, 2 to 3 flowered. Glumes light browngreen or yellow-green with tips and margins often tinged with pale to dark violet. Lemmas light or dark green with dark veins.

Habitat Var. caerulea is found in a variety of moist and wet conditions. By contrast , var. viridiflora is only seen in wet or very wet habitats and often in areas fed by springs . Close associates include Filipendula ulmaria , Eupatoria cannabinum, Holcus Lanatus and Phragmites australis. In addition to its moisture tolerance, it is a plant of shade. On Tuddenham Heath v .c. 26 its distribution is frequent under considerable shade of silver birch in very boggy conditions of spring fed sand . Var. caerulea is not present. On the Old Fen, Thelnetham v.c. 26 , it is on the margin and in the shade of alder carr in black peat with a high water level. At Pashford Poors Fen, Lakenheath , v.c. 26 , it is in marginal shade of willow and silver birch on spring fed rides. In fen carrs with low shrub canopy , var . viridiflora does not produce a flowering culm until the plants reach the open margin; but on a woodland ride in sand under an open but high tree canopy at Benacre v.c. 25 , several plants were in flower but stunted in height. Infrequently one or two plants will be seen in the open on the margin of a carr , with the only shade offered by a small tree; a silver birch at Hurst Fen , v.c. 26. I have seen a similar phenomenon in Scotland on the stony shore of Loch Tay ; a single plant of var . viridifiora under the shade of an alder. Do these plants which break bounds have a short life?

In addition to the tolerance of excessive moisture and shade, this variety , as with other Molinia , is acid tolerant . On Tuddenham Heath v.c. 26 , a fine sand aggregated by organic matter mainly comprising undecomposed roots , has a very acid pH of 4·4. Not far away on Cavenham Heath, water from a higher source finds its way down to a gulley by the track traversing the heath.

Here in a depression on the margin of low scrub growth , the soil is an organic silt with a proportion of fine silt washed down from a higher elevation and the pH is slightly acid (6·4) .

Trans . Suffolk Nat. Soc. 26 (1990)

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Suffolk Natural History, Vol. 26

Cultivation and Seed Experiment A plant of var. viridifiora was taken from the wild and put into cultivation at the end of October. Very shortly the leaves and culms turned a golden-brown (Molinia is deciduous in winter). New growth appears in late April when leaf developement is very slow . By mid-May leaves have grown 5-12cm with some at 18cm by the end of the month . Culms appear at the end of June and the panicles break the sheath towards the end of July and remain closed to the rachis until about mid-August. This plant produced green lemmas as in the previous year.

From this plant , seed was taken in early November and after drying, planted the same month. The culms appeared in June with the difference that they were short in a dry garden soil. In early August , the inflorescences showed green lemmas: the seed of the variety had bred true.

Acknowledgements I thank Dr. Martin George of the Nature Conservancy Council for his permission to record observations at Cavenham and Tuddenham Heaths . I also thank Mr. Derek Moore for my continued access to study on reserves of the Suffolk Wildlife Trust and Dr. Max Walters for making observations on the MS .

References Conert , H . J . (1961) . Die systematik und Anatomie der Arundinea, 182.

Weinheim .

Hind , W. M . (1889). Molinia caerulea Moench , in The Flora of Suffolk , 398, London .

Sell, P . D . & Trist, P . J . 0 . (1988) . Molinia caerulea subsp . altissima (Link) Domin, in Two subspecies of Molinia caerulea (L.) Moench in the British Isles, Watsonia , 17: 153.

Swann , E . L. (1975) . Molinia caerulea (L.) Moench , in Supplement to the Flora of Norfolk, pp. 59- 60. Norwich .

Trist , P. J. 0. (1959) . Molinia caerulea var. subspicata Figert , var. arundinacea (Schrank) Aschers & Graebn . and M . litoralis Host , in An Ecological Flora of Breckland, 98. Wakefield.

P. J . 0. Trist , 28 High Street , Balsham, Cambridge , CBl 6DJ

Trans. Suffolk Nat. Soc. 26 (1990)