Sea pea Lathyrus japonicus

 

Watsonia 1977.   R. E. RANDALL 

L. japonicus is a creeping or climbing perennial most commonly found on shingle beaches but occasionally recorded from dunes and other coastal habitats. It is fairly long-lived and once established it is not likely to disappear except where coastal changes or human pressure cause this to occur. Where beaches are accreting seawards and more closed vegetation enters as humus builds up, it disappears on older shingle but persists nearer the shore where the vegetation is open. 

 Its seeds are avidly eaten by birds, and many animals, especially sheep, find the whole plant palatable. Brightmore & White (1963) suggest that an exceptional spread of L. japonicus at Rye Harbour from 1962 until 1964 resulted from dispersal of seeds by flocks of stock dove, Columba oenas.

 The plants cease flowering and soon die when heavily or frequently trampled.

In eastern E. Sussex, V.c. 14, and E. Kent, v.c. 15, L. japonicus is much more abundant. In the former it is present in great quantity for over 3 km of shingle from Winchelsea Beach to Rye Harbour and on to Camber Sands, where it becomes a dune species. It is most abundant on new shingle ridges but persists locally as these become covered with blown sand east of the estuary of the River Rother. East of Dungeness power station, E. Kent, there is a colony which has increased considerably between 1946 and 1973, though two other colonies nearby known in the 1940s have now apparently disappeared. Along this stretch of coast, especially at Winchelsea and Dungeness, pressure from tourism and fishing have made some colonies poor or non-flowering, but at Palmarsh, west of Hythe, a colony first recorded in 1954 on the rifle-range is expanding. 

Elsewhere in E. Kent, L. japonicus is now absent from its old sites at New Romney, Kingsdown and Reculver, although it still persists at Walmer and at Whitstable, where it was first recorded in the 1970s. Walmer beach is heavily used by holiday-makers but there is a wooden track across the shingle to which most visitors keep. This has reduced the pressure on the beach vegetation and the colony of L. japonicus is expanding. Perhaps this augers well for future conservation of the species and suggests a satisfactory means of reducing trampling on the species at other sites.

'Native. Shingly shores; very rare. In some stations it seems to be extinct; but it may still be found at Dungeness and Kingsdown, in small quantity.' (Hanbury & MarshaIl 1899)  

Coastal vegetated shingle structures of Great Britain  1993

England appendix

Key 

SH119 Rubus fruticosus - Arrhenatherum elatius scrub community; 

SH71 Arrhenatherum elatius (false oat grass) grassland community; 

SH68 Festuca rubra - Plantago lanceolata - Poa pratensis community; 

SH66 Festuca rubra - Plantago lanceolata - Lotus corniculatus community; 

SH48 Festuca rubra - Hypnum cupressiforme (moss) - Lotus corniculatus - Plantago lanceolata community; 

SH44 Dicranum scoparium  (moss)  - Rumex acetosella -Aira praecox (early hair-grass) community; 

SH11 Lathyrus japonicus (sea pea) pioneer community; 

SH8 Senecio viscosus - Glaucium flavum (yellow horned-poppy)  - Rumex cripus littoreus pioneer community. 

SH39 Silene vulgaris maritima (bladder campion) - Arrhenatherum elatius   moss- and lichen-rich community;