The goal of the management of naturalistic herbaceous vegetation is to achieve a satisfactory balance between maintenance costs and the appearance and persistence of the sown or planted species. As a result, the management of such plant communities requires a greater understanding than traditionally planted herbaceous vegetation but generally substantially fewer maintenance hours. The reason for this dichotomy is that in traditional herbaceous planting the objective of management is very clear; any colonising plants that are not part of the original planting scheme are weeds to be removed. The practice of maintenance is in effect to maintain a plant community in a state of suspended animation. Plants that fail are replaced and gardened until they succeed. This may be highly demanding of labour but the objective is clear even to the most unskilled gardener or manager.
With naturalistic vegetation, managers need to recognise that suspended animation is not a realistic concept, some plants will succeed, some will fail, and some of the former will colonise territory (by seeding or vegetative means) vacated by the latter. Species that were not included in the establishment mix will establish; some of these will be welcome (or at least acceptable), others will be unacceptable. The role of the manager therefore involves walking a tightrope between what is perceived by them and members of the community to be acceptable or unacceptable. Unless there are abundant resources for management, there is, however, no longer a simple stereotype to manage towards. There may be many different points on the gradient from acceptable to unacceptable. Management becomes the art of defining the limits to acceptable change.
Judgements on this will depend not just on the values of the manager but also on their perception of how site users feel about the vegetation, which, in turn, will be dependent upon the site’s context and role. The final arbiter in this decision-making soup will be biological and, in particular, the impact, for example of invading plants or animals, on the capacity of the desired species to persist and do what they were selected for. Managers can only make this latter judgement satisfactorily if they have experience of what is likely to happen, backed up by a scientifically based ecological and horticultural understanding of the impact of factors such as weed density and slug grazing on the persistence of a given species.
From an intellectual perspective, this is much more professionally challenging than the management of conventional decorative herbaceous vegetation. Do vegetation managers see it this way? People who are capable of integrating these intellectual and practical aspects appear to be very uncommon in public landscape management where the world is dominated by generalists with very limited depth in vegetation management per se. The richest vein of managers with these skills exist as head gardeners in large private and institutional gardens, and as managers of semi-natural vegetation of high-conservation significance. Few of these people are likely to choose to ply their trade in the world of public green-space management and landscape contracting, where extraneous factors often severely restrict what can be achieved. These problems are not restricted to Britain, as Hein Koningen describes in Chapter 10.
The successful management of herbaceous vegetation obviously starts at conception; if inappropriate species or communities are chosen, then management is almost doomed to fail from the outset.
Management to aid the persistence of desired species
Assuming that species are broadly well-fitted to the site, there are three factors that primarily determine persistence: typical longevity-capacity to establish offspring, competitive displacement by other plant species, and predation by herbivores such as slugs and snails.