In developing my ideas for the perennial meadow

Scampston Hall, UK, perennial meadow, design Piet Oudolf.
In developing my ideas for the perennial meadow it is this dilemma which has lead to the concept of theme plants. I restrict myself to a maximum of five, but do sometimes bend the rule by using different species or cultivars of the same genus. I have a grassy meadow in my own garden using low growing molinia grasses, but have ended up using three different cultivars to increase the diversity without diluting the idea. In another place, I have adjacent borders using the same planting scheme, but in one I use a tall growing pennisetum grass and in the other, another, more arching, cultivar. These theme plants are randomly planted at intervals across my schemes to create a matrix within which the other theme plants are spread to create a block of vegetation that as a whole represents my main idea.
If perennials have one weakness it is that they are dynamic and this, of course, is one of their strengths as well. In spring they start growing, later they flower and when this ceases they tend to slip into a decline. If carefully chosen we can extend the period our schemes look presentable by including plants that not only look good in flower but both before this starts and, later, when maybe they make seed heads. Inevitably perennials die back and this means as structural elements within a garden's design they are weak. This weakness was shared by the traditional herbaceous border, however, these were typically presented within a strong framework, often created by a wall or hedge as background. However, our new-look perennial borders with their need to draw us into the ideas they foster need to be entered and not presented as an abstract tableau set within a picture frame.
To overcome the weaknesses I see in perennials I follow a number of strategies to create year round structure. Firstly, I select some plants that stand up throughout the winter months such as miscanthus grasses and monardas. Secondly, I organise the meadow into a series of crisply defined beds separated by bold purposeful paths. And, finally, I create a framework of some sort; perhaps with shrubs, hedges or fencing that define the internal structure of the garden.
Such beds can be arranged into a labyrinth that leads visitors on a journey amidst the plants they contain and even in small gardens this can be made to work. Admittedly, these scaled down schemes lack the grandeur of the parkland meadows we seek to emulate, but when the plants are well chosen and grouped as I have described they are more than capable of presenting a clear idea that can exert a powerful influence upon the garden spaces they occupy.