by Graham Easy (again without mention on the cover!). It includes many of the aliens
that have moved in recently, discusses the taxonomy and ecology of the taxa and has
10km sq. distribution maps. For definitive keys to aquatic plants we have the British
Water Plants, AIDGAP Field Guide. Haslam, Sinker & Wolseley Field Studies Council,
1987. This has illustrated keys and drawings of each plant. Alien aquatic plants, in
common with trees and scrubs, are commonly imported and planted in garden ponds
and lakes and often get out into semi-natural ponds. A useful book I picked up second-
hand in this respect is Aquatic Plants of the United States, Muenscher. Comstock
Pub.Co. Inc. 1944. with superb line drawings and keys! Apopular group among botanists
and non-botanists alike, the Orchids, give a lot of trouble to recorders as without careful
examination of flower structure it is easy to come unstuck (see part one of this article!).
To my mind the large format Orchids of the British Isles, Foley & Clarke, Griffin
Press, 2005 - with its fabulous photographs, maps and diagrams is the most useful. A
cheaper alternative is the Field Studies Council Guide to Orchids AIDGAP key folded
card. Before getting finally onto trees and shrubs, I must just mention that BSBI News,
the newsletter of the BSBI, has accumulated over the years, large numbers of line drawings
of alien plants found in the U.K., and numerous generic keys. If you ever get the chance
to buy a second-hand set -jump at it!
Books on tree and shrub identification
Unfortunately, although there are numerous well-illustrated books on trees, very few
have definitive, easily assimilated, descriptions or keys, to permit unequivocal
identification. To complicate matters, large numbers of different tree taxa have been
imported from abroad as specimen trees in arboreta, or have been planted in woodlands,
parks, public gardens and private garden collections. Of these a high percentage have
been further selected for habit, colour or leaf shape and designated as 'varieties' or
'cultivars'. Furthermore, many exotics are passed off as natives by supply companies.
At the present time for example a range of Japanese and American birch species are
being planted on new housing estates and labelled Betula pendula''.
The best book for the beginner is undoubtedly the Reader's Digest Guide (Field Guide
to the Trees & Shrubs of Britain. Reader's Digest Nature Lover's Library, 1981.
London), reprinted in 2004 and still available in Waterstones. It gives a good range of
both native and introduced taxa, superbly illustrated, and a good range of comparative
descriptive features, including illustrations of buds and twigs. The Collins Tree Guide,
Johnson & More. Harper Collins, 2004 is also a superb book in that it has paintings of
just about every cultivar of native and exotic tree likely to be planted in the U.K., but the
descriptions are cryptic and more often than not do not allow unequivocal identification.
To LD. a tree one has to wade through pages of illustrations for a rough match and then
extract key features as a set of notes in order to weigh up the evidence - and even then
doubts may linger as features may be mentioned for one taxon and not for another. The
magnificent large format Cassells's Trees of Britain & Northern Europe, More and
Essex Field Club Newsletter No. 57, September 2008 13