An annual predominantly found in arable fields, where it can be a weed, but also recorded from road verges, trackways and quarries. It has a more permanent niche in some tightly grazed grassy or grass-heath habitats. It occurs in waste ground as a casual from wool shoddy and imported aggregates, and as a seed impurity. Lowland.
The distribution of A. interrupta, which was first recorded in the wild in 1848, seems to be stable or even increasing, at least at the 10-km square scale. The seed is long-lived and disturbance is the key to its survival.
A Eurosiberian Southern-temperate species.
Light (Ellenberg): 9
Moisture (Ellenberg): 5
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 6
Salt Tolerance (Ellenberg): 3
January Mean Temperature (Celsius): 3.4
July Mean Temperature (Celsius): 15.9
Annual Precipitation (mm): 671
Height (cm): 40
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 104
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.8
Scarce Atlas Account
Apera interrupta (L.) P. Beauv.
This grass is a shallow rooted, lowland annual of arable land, which also colonises road and rail verges and chalk and gravel excavations. It is mostly confined to field headlands but has become a troublesome weed at a few sites. More significantly, there are a number of long established populations on grassland or heathland where mammals have maintained a close-cropped habitat. On trackways and heathland it is usually a very low plant growing alongside Arenaria serpyllifolia, Catapodium rigidum and Sagina procumbens, attracting attention only by its silky green coloration which is especially noticeable when other species have blanched in the sun. In contrast, in the enriched arable soils it is usually a tall, leaning grass half a metre high.
This annual grass produces a large number of lightweight grains, each with a long, rough-awned lemma which should facilitate a wide dispersal. However, the inability of the seeds to germinate where any sort of competition from established plants exists restricts its spread. Longevity of seed enables it to survive at its strongholds, where it often appears after an apparent absence of several years, and explains its frequent appearance after soil disturbance where long buried seeds are brought to the surface.
Probably native only on the light soils of eastern England. Other records are mainly of a casual nature or are the result of introductions with agricultural seed, wool-shoddy or aggregates from gravel pits where the plant grows as a native. At these sites it is usually a short-lived invader which fails to survive competition from other species.
A. interrupta is patchily distributed across Europe and North Africa to Asiatic Russia and has been introduced into North America (Hubbard 1954).
In ancient times it may have grown on sheepwalks on the sands and chalklands of eastern England. Easy (1992) presented evidence that this is a native species; it is described as introduced by Stace (1991) but not by Kent (1992).
G. M. S. Easy