An annual, most frequent on drying mud but found in a wide variety of habitats associated with freshwater, including the margins of ponds, ditches, reservoirs, turloughs and flooded gravel-pits. It has also recently been found as a weed in aquatic garden centres. Lowland.
A. aequalis has been lost from many suitable sites, but seems readily to colonise new open habitats. Population sizes are very variable, and it may not appear when water levels remain high, possibly leading to under-recording. It may sometimes be overlooked as, or mistaken for, A. geniculatus. It was not discovered in Ireland until 1992.
Circumpolar Boreo-temperate element.
Light (Ellenberg): 8
Moisture (Ellenberg): 9
Reaction (Ellenberg): 4
Nitrogen (Ellenberg): 7
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.5
July Mean Temperature (Celsius): 16
Annual Precipitation (mm): 717
Height (cm): 40
Perennation - primary
Perennation - secondary
Life Form - primary
Life Form - secondary
Comment on Life Form
Clonality - primary
Count of 10km squares in Great Britain: 298
Count of 10km squares in Ireland: 3
Count of 10km squares in the Channel Isles: 1
Atlas Change Index: -0.33
Scarce Atlas Account
Alopecurus aequalis Sobol.
Status: not scarce
This species is found on the margins of shallow ponds, of gravel pits and of reservoirs, always in the proximity of fresh water. It is not often seen in shallow water but occurs on mud as the water level recedes. In some of the Breckland meres, where the water level fluctuates markedly from year to year, it can occur in great abundance. Its associates in these meres include Agrostis stolonifera, Chenopodium rubrum, Juncus articulatus, Mentha aquatica, Myosoton aquaticum, Oenanthe aquatica, Persicaria amphibia, Phalaris arundinacea, Potentilla anserina, Rorippa amphibia, R. palustris, Rumex maritimus and Sagina nodosa.
It is an annual plant, which reproduces by seed. Culms ascend from a decumbent base and root at the nodes, a habit which adds to the density of the colony. Populations vary greatly in number from year to year, being largest when water levels are low and much mud is exposed. In years of high water level the plant may only be present as dormant seed.
In the long term this species may be considered under threat. Old ponds have been reclaimed and many wet habitats have been drained. Suitable remaining habitats are in danger of pollution. It has, however, recently been seen as a weed in a number of aquatic garden centres and it might therefore be expected to spread into garden ponds.
This is a widespread species which occurs in the boreal and temperate zones throughout the northern hemisphere. In Europe it is rare in the oceanic western fringe and virtually absent from the Mediterranean region.
P. J. O. Trist