Eleocharis parvula

Dwarf Spike-rush

Eleocharis parvula R Avon Devon Aug 1998 crop sm
E. parvula, River Avon, Devon, August 1998 (Roger Smith)


Cromarty Firth, late June

Overview

  • a very small plant, ‘squatter’ than acicularis, shorter-stemmed, though stems fractionally less thin
  • patch-forming
  • spreads by stolons at/near the surface, whitish, and ending in small tubers
  • often shy-flowering: many populations said to flower rarely or not at all
  • spikelets tiny, short, and few-flowered
  • lowest glume encloses base of spikelet, and is at least half as long as spikelet
  • stigma 3-forked (as in multicaulis and parvula; contrast uniglumis and larger species, 2-forked)
  • ripe nut smooth (unlike acicularis); style-base tiny, confluent with nut (again unlike acicularis)
  • very local indeed, on estuary mud only

Growth

~ makes open or sometimes dense patches; often vegetative only; can make extensive sheets in sheltered bays


closer view of individual plants, Cromarty Firth

~ spreads by stolons at/near the surface, whitish, and ending in small tubers: a distinctive difference from acicularis

Eleocharis parvula SM 2105 sm (1 of 1)
showing stolon with white tuber (above, Robin Walls; below, Roger Smith)

Eleocharis parvula Beaulieu Aug 1981 crop 2 sm

Stems
~ up to 8 cm but often much shorter
~ 0.3-0.5 mm wide

Eleocharis parvula R Avon Devon Aug 1998 - 2a crop sm
River Avon, Devon, August 1998 (Roger Smith)

Eleocharis parvula 7861 sm
Gwynedd, early September (Robin Walls)

Spikelets
~ short, ovoid, few-flowered
~ lowest glume at least half as long as the spikelet, and encloses its base
~ glumes pale cf.
acicularis

E-parv2 sm
Gwynedd, early September (Robin Walls)


Flowers
~ stigma 3-forked
~ perianth bristles (usually) 3, longer than nut

Nuts
~ small (1-1.4 mm)
~ style-base (stylopodium) tiny, not swollen, confluent with nut

Habitat
~ grows only in bare sheltered estuarial mud. Robin Walls informs me that at a site near Christchurch (below) the plant occurs in what must be only slightly brackish water, and is exposed only on low spring tides. Conversely, at Penmaenpool in Gwynedd the site is in small pools at the highest level of the saltmarsh, often dry, and only inundated on spring tides: opposite extremes!


Cromarty Firth near Dingwall; E. parvula abundant on the open mud, with Callitriche sp. only associate;
fringing vegetation is
E. uniglumis, Triglochin maritima, Bolboschoenus maritimus, Phragmites

Eleocharis parvula SM 2101 sm
Dorset; E. parvula revealed on bare mud at low spring tide;
fringing vegetation
Bolboschoenus maritimus and (beyond) Phragmites
(Robin Walls)


Frequency & range
~ very localised indeed; some newly-discovered sites far from those previously-known, so perhaps still overlooked.
See distribution map.

Links to the other Eleocharis spike-rush pages (also accessible from the sidebar)