With something as complex and variable as vegetation, no key can pretend to offer an infallible short cut to diagnosis. The following should thus be seen simply as a crude guide to identifying the types of heath vegetation in the scheme and must always be used in conjunction with the data tables and community descriptions. It relies on floristic (and, to a lesser extent, physiognomic) features of the vegetation and demands a knowledge of the British vascular flora and, in many cases here, of bryophytes and macrolichens. It does not make primary use of any habitat features, although these may provide a valuable confirmation of a diagnosis.

Because the major distinctions among the vegetation types in the classification are based on inter-stand frequency, the key works best when sufficient samples of similar composition are available to construct a constancy table. It is the frequency values in this (and, in some cases, the ranges of abundance) which are then subject to interrogation with the key. Most of the questions are dichotomous and notes are provided at particularly awkward choices or where confusing vegetation patterns are likely to be found.

Samples should always be taken from homogeneous stands with 4 x 4 m generally sufficing to encompass the scale of the vegetation. Complex mosaics may demand samples of identical size but irregular shape, while very small stands can be sampled in their entirety.

1 Ulex gallii or U. minor constant and often abundant with Calluna vulgaris and Erica cinerea 2

Calluna and E. cinerea can be frequent and abundant but without U. gallii or U. minor 20

2 U. minor present without U. gallii 3

U. gallii present without U. minor 8