An annual of old walls and bare ground on calcareous or neutral substrates. It is intolerant of competition, and is susceptible to nutrient-enrichment. It may occasionally occur as a casual or short-term introduction well outside its normal range. Lowland.
G. parisiense was first recorded in Britain in 1690. Always scarce, and lost from many 10-km squares before 1930, it has undergone further decline since the 1962 Atlas as many of the open, infertile soils on which it grew have undergone agricultural improvement and ancient walls have been cleaned, re-built or demolished.
Light (Ellenberg): 8
Moisture (Ellenberg): 3
Reaction (Ellenberg): 7
Nitrogen (Ellenberg): 2
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 3.7
July Mean Temperature (Celsius): 16.3
Annual Precipitation (mm): 693
Height (cm): 30
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 63
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: -0.57
Scarce Atlas Account
Galium parisiense L.
G. parisiense is a small annual of bare ground and walls, where it occurs alone or in the company of Arenaria serpyllifolia, especially subsp. leptoclados, Catapodium rigidum, Erophila spp., Sagina apetala, Saxifraga tridactylites and various mosses and lichens. The flowering plants listed are all shallowly rooting species which cannot survive if the habitat becomes sufficiently enriched to allow the establishment of more vigorous competitors. Trist (1979) lists as associates of G. parisiense a number of larger or perennial species recorded within the same square metre; it must be assumed that these constituted a fairly closed vegetation in which the smaller annuals were confined to the discontinuities.
G. parisiense can reproduce only by seed. Germination is triggered by a spell of warm weather following a wet period. In the Mediterranean climatic regime germination is always in spring, whereas in Britain it can also occur following unusual weather conditions in summer and autumn. Seed is set within two or three months of germination. Where the plant occurs on walls, subsidiary colonies may often be found at the base if there is suitable gravel, but it has no way of spreading further. Autumn-germinated plants on the ground are likely to be killed by frosts.
The colonies of G. parisiense on old walls are probably well recorded, whereas plants on the ground are much more easily overlooked. The outlying locality in Devon, discovered in 1954, is of this type, but as the plant lasted only until 1966 (Ivimey-Cook 1984) it might represent an accidental introduction. The nature of such accidents is extremely obscure. Some are indicated by the crosses on the map and others are hidden among the circles, most notably a colony at Tottenham, on the concrete remains of sewage filter beds, discovered in 1984 and still thriving in 1992. There may be other colonies of this inconspicuous plant waiting to be found in unexpected places.
Outside Britain, G. parisiense is common in the west and central Mediterranean region, but rare north of the Alps. The most northerly localities in Germany are even more isolated than the British ones (Haeupler & Schonfelder 1989). It is tempting to speculate that this species was able to spread rapidly northwards in western and central Europe during the period of warmer climate between 1150 and about 1300 (Lamb 1977), and outside its main range has been steadily decreasing ever since. This suggestion is supported by the observation by G. Beckett (pers. comm.) that five of the six old walls in west Norfolk where it still grows are of no later than 13th century origin.
R. M. Burton