FIG 44. Tresco Abbey Gardens, April 2005. (Rosemary Parslow)
great range of plants from countries with a Mediterranean climate, Australasia, the Canary Islands, South Africa and parts of South America (see Chapter 13). Visitors to the Abbey Gardens will also remark on the extraordinarily tame birds. In 2004 the entrance to the Gardens was updated and the tea room moved. If you visit the tea garden, kamikaze robins Erithacus rubecula snatch crumbs from your lips and blackbirds, chaffinches Fringilla coelebs and other birds will help themselves to cake from your plate. At certain times of the year the odd appearance of the house sparrows Passer domesticus, starlings Sturnus vulgaris and blackbirds – with bright yellow caps of pollen from drinking the nectar of Puya chilensis plants – has occasionally led to them being identified as something far more exotic! Another curious phenomenon in the former tea garden was the pecking of holes in the mortar of a wall by dozens of house sparrows, presumably seeking minerals after the manner of some tropical parrots.
Some of the exotic plants that grow around Tresco and the other islands are spread intentionally when people take cuttings or seeds to cultivate for their own gardens or pass around to their friends. Other plants escape from the Gardens by natural means, blown by the wind or otherwise carried accidentally, to end up elsewhere in the islands. Many of these are now established as part of the Scillonian flora. Perhaps the most unusual inhabitants of the Gardens are the two species of New Zealand stick insects that have been part of the fauna for about a century and are now found elsewhere around Tresco. Recently they have also reached St Mary’s. Also from New Zealand but less obvious are the woodland hoppers Arcitalitrus dorrieni, the little back amphipods that now live under every rock and log on the island. These are the most obvious and well-known examples, but there are many other insects and other invertebrate species that originally arrived as stowaways with horticultural material from abroad.
It is not just insects and other animals that have arrived in Scilly with introduced plants. A series of discoveries of rare introduced bryophytes began in 1961 when Miss R. J. Murphy discovered two unexpected liverworts on Tresco, Lophocolea semiteres, new to the northern hemisphere, and a new species of Telaranea that was named T. murphyae after her by Mrs Paton in 1965. Telaranea murphyae may have been introduced to Tresco from the southern hemisphere, as has happened with many other species such as Lophocolea semiteres and L. bispinosa, which are found only on Scilly and in Scotland, pointing to introduction with exotic plants. Besides Lophocolea bispinosa, found by Mrs Paton in 1967, was a moss Calyptrochaeta apiculata, later also found in East Sussex.
Since then, the moss Sematophyllum substrumulosum was first recorded as new to Britain on several of the islands (it has since been discovered to have been found, but not identified, in West Sussex in 1964). It was growing on the bark of Monterey pine in 1995 and again may have arrived with horticultural material (Paton & Holyoak, 2005). Other species recorded have included two mosses rare in Britain (Chenia leptophylla, Didymodon australasiae) and another that has become very widespread and common (Campylopus introflexus). By 2003 some of the alien bryophytes had greatly extended their ranges since the 1960s, with both alien Lophocolea species now widespread throughout the islands, and Telaranea murphyae had spread from Tresco to St Mary’s.
ST MARTIN’S
St Martin’s is a long narrow island with a mainly west-to-east axis. It is just over 3km long by 1.5km wide and covers 238 hectares if you include White Island (15ha). First impressions of St Martin’s are of long, empty white beaches (Fig. 45), intense turquoise sea, little clusters of houses tucked into the hillside and the strangely modern-looking (it actually dates from 1683) conical red and white banded tower of the daymark on high ground on Chapel Down at the eastern end of the island.
FIG 45. The south coast of St Martin’s, looking towards Tresco at low tide with the sand flats exposed. June 2005. (Rosemary Parslow)
As on St Agnes, the individual hamlets are named, rather unoriginally, Lower, Middle and Higher Town. They are strung out along the two-kilometre concrete road from Lower Town quay in the west to Higher Town Bay and New Quay, just over halfway along the length of the island. Beyond the farmland to the east the land rises up to the heathland on Chapel Down. Heathland also extends all along the northern edge of the island; only the insert of the dune grassland of the Plains and in some places wetter areas and a small pool break the continuity. Around the higher and exposed land are rocky promontories and cliffs where seabirds nest. Looking northeast from the cliffs on a clear day you can often see the cliffs of Land’s End, 45km away.
The southern shores of St Martin’s are mainly sandy, with sand dunes and just a few stretches of low cliff. Along the back of the dunes at Higher Town Bay are small bulb fields, frequently inundated by blown sand (Fig. 46). Indeed, much of St Martin’s is composed of blown sand that has been deposited over the whole top of the island in the past. This has led to some of the most impressive arable weed populations in Scilly being found here, including unusual species not found elsewhere in the islands. The sandy soils are also found around Higher Town Bay, where the cricket field is mown maritime grassland dominated by
FIG 46. Bulb fields with rosy garlic Allium roseum, whistling jacks and great brome, St Martin’s, May 2003. (Rosemary Parslow)
chamomile and several species of clover, including both suffocated Trifolium suffocatum and subterranean clover. The cricket field is low-lying and sometimes floods completely – perhaps not ideal for the cricket, but maybe why there is a superb show of chamomile most summers. The sand-dune areas around the quay and along the track ways are also places where some rare clovers are found. Suffocated clover can be difficult to find, as blown sand often drifts over the plants and completely buries them. It also flowers early in the year so has usually dried up and disappeared by early summer. In the corner of the cricket field is a small brackish pool, sometimes covered by the pretty white and yellow buttercup flowers of brackish water-crowfoot.
The dune system along the Higher Town Bay is typical of the NVC (National Vegetation Community) SD7 semi-fixed dune, relatively species-poor but with some interesting herbs such as balm-leaved figwort and Babington’s leek. In places bracken and the evergreen shrub Pittosporum crassifolium are invading the dune. A sub-prostrate form of wild privet occurs along the edge of the track. There are species of unstable foredune habitats such as sea rocket Cakile maritima where there are breaks in the dune. In summer this is one of the best places to see ringlet butterfly Aphantopus hyperantus, a recent arrival in Scilly. At the back of Lawrence’s Bay is a low cliff with a hanging curtain of the succulent Sally-my-handsome Carpobrotus acinaciformis, with its distinctive curved leaves and carmine flowers.
There is a series of rocky headlands with exposed rocks and thin soils along the north side of St Martin’s. Wind-eroded heather and gorse heathland cover the area between Top Rock Hill and the separate group of the Rabbit Rocks. The slopes below the hill are covered with bracken and gorse communities on deeper soils and a fringe of maritime grassland towards the coast. At Round Bowl both small adder’s-tongue fern and orange bird’s-foot have been recorded, but the dune is being invaded by heath and scrub species in this area. Pernagie is a group of small bracken fields below the hill with maritime grassland and a small area of heathland at Pernagie Point. The westernmost headland on St Martin’s is Tinkler’s Hill. The top of the hill has a cover of gorse scrub surrounding a smaller area of heather. At the bottom of the hill is heathland and coastal grassland alongside Porth Seal, where small adder’s-tongue fern may be found. Porth Seal is a geological SSSI on account of the raised beach