Complementary Plants for Perennial Meadows

This will be the penultimate post in the Meadows 101 section of this site, but in many ways it is one of the most important. This series of posts aims to give an introduction to the ideas and practices of creating naturalistic perennial meadows in modest sized garden landscapes. I hope to inspire others to have a go and share their experience of this exciting aspect of garden design with me and the other followers of the site.

The theme plants in our perennial meadows are chosen to grow well together to form a coherent block of vegetation that looks good for as long a period of the gardening year as possible. Ideally they should perform together to create a sequence of highlights – flowers I mean – to hold our interest. If it is the theme plants that create the backbone of our perennial meadow plantings, then it is the, so-called, complementaries that introduce the magic.

Perennial meadows mimic nature by repeating their theme plants across the ground surface to create a bold, evocative atmosphere. The danger, and I have seen it on a number of occasions, is that the planting scheme becomes monotonous like green wallpaper rolled out to decorate the landscape; it is complementary plants that are the answer.

The term, complementary plants, is my own, but it is rather difficult to define as these plants are used for a number of different reasons in my planting schemes – let’s go through some of them:

• Extending the schemes season of interest. The best example of this is a prairie style scheme using perennials that flower from mid summer onwards. If these are the only theme plants you use then the meadow will look very dull/green for most of the spring and the first half of summer. The answer is the addition of either spring flowering bulbs or perennials that flower in spring and tend to go to sleep for the rest of the year. Spring flowering bulbs abound with tulips and daffodils being the first we think of, but there are many other bulbs to use to follow on, such as ornamental onions. Further, many perennials originating from deciduous woodland conditions flower in spring to take advantage of available sunlight. Some, such as mertensia, die down later and others simple tick over all summer as an understory to anything growing taller than themselves – in either case they will function as valuable complementary plants in our meadows, bringing colour and interest sooner than many other perennials.
• Add variety. A well designed perennial meadow should project a coherent image that registers at a distance. If you start walking nearby and all you see is the same four or five plants repeated over and over again, no matter how well chosen, they are going to start waning in interest. Complementary plants that pop out here and there prevent this happening and as keen gardeners here is a way to sneak in those impulse purchases that we didn’t really have a place in mind for when we allowed passion to rule over logic. The danger here is that we need to take care with what we add. All too often this group of complementaries ends up growing too vigorously or distracting from the schemes in my own garden.
• Linking. This is a common practice of all good garden designers. Use the same plant in different parts of you garden and link together its different parts.
• Creating a secondary or counter theme. This is similar to the idea of linking just mentioned, but here we may be distributing another plant throughout our main scheme to create a subtle variation or in order to merge two adjacent schemes together by selecting one plant and using it in both areas. This is where the process of perennial meadow gardening moves away form the dogma of its formula into the intangible arena of magic and music.

Returning to practicalities, in order for the theme plants to function they need to be present in sufficient numbers, which means ideally that they should fill no less than 75% of the available area. This means that we need to develop strategies for not only calculating how many plants (both theme and complementary) we need, but also how we are to go about arranging them on the ground.

My meadows use around 8 plants per square meter/yard and when the schemes include some large growing species this number tends to drop down to around 6. Knowing the surface area of a meadow and the numbers of each theme plant needed per square meter/yard it is a simple matter to calculate the total numbers. These numbers need then to be reduced to allow space for the complementary plants we decide to introduce. This could be one for one in the case of typical summer flowering perennials, but for ephemeral spring flowering species and bulbs which die down a few weeks after flowering there is hardly any need to decrease the numbers of theme plants at all. Some rounding up and down is the order of the day here and my experience suggests that with a mix of complementary perennials and spring flowering bulbs a reduction of between 10 and 15% in the numbers of theme plants is about right.

When it comes to setting out a meadow with a mixture of theme and complementary plants the complementaries are usually set out first as their distribution is often not even over the total area, but maybe confined to a part of it or to the edges. I then distribute the theme plants starting with the largest and most dominant species and filling in with the smallest. Finally, following planting, the bulbs can be dropped into the gaps left between the other plants.

To write about using complementary plants in a perennial meadow is far more difficult than recognizing their contribution when it has been carried out well. Some gardeners will do this type of tweaking intuitively, but with just a little forethought it is really not beyond the reach of most of us.