Good Plant Association or Companion Planting
One of the biggest changes in twentieth-century garden-making, has come about through our increased awareness of how important it is to group plants that go together well. In the right company the beauty and effectiveness of a plant can be greatly enhanced; with the wrong companions the reverse can happen.
At one time it was thought that good plant association (the gardeners’ term) meant keeping plants of a siilar kind together — hardy perennials in, shrubs in shrubberies, trees in arboretums, roses in rose gardens, and so on. Two factors have destroyed that notion: one the decreasing size of gardens, which has made it physically impossible to segregate plants in this way, the other a growing realization that the contrasts between plants of totally different character can be used positively to devise effective arrangements.
So the idea of the mixed border was born and prospered exceedingly. Shrubs form the permanent framework,provide variety of form and colour, and roses and bedding plants help to maintain colour much more continuously and for a longer period than would be possible without them.
Mixing Colours and Forms
In all plant associations there are two major factors to be considered: colour and form. Colour is a particularly emotive subject and people react to it in highly personal ways. Some cannot stand white, often explaining that it reminds them of funerals. Many are irritated by bright yellow or orange, depressed by blues and purples or find reds vulgar and dominating. How is it that colours can exert such a range of impressions? All the colours that we see can be made by mixing three primary colours, red, yellow and blue. At full saturation these colours, in association, produce the strongest contrasts, but their effect can be diminished either by lowering or increasing their luminosity, the one making them appear much duller and blacker, the other much lighter or closer to white. Mixtures of any two of the primaries will produce intermediate colours — orange when red is mixed with yellow, green from yellow and blue, and purple from blue and red. Mix all three primaries and you get the endless varieties of muted shades which eventually lead, by way of the browns and greys, to black.
We can see something of how this works by making a colour clock. Red occupies a segment at 12 o’clock; pure blue is at 4 and pure yellow at 8. At 1 is violet-red, at 2 violet, 3 blue-violet, 5 blue-green, 6 green, 7 yellow-green, 9 yellow-orange, 10 orange, 11 orange-red. The clock shows which colours will produce contrasts and which harmonies, and just how strong or soft those contrasts or harmonies will be. The nearer together the colours are on the clock, the softer the harmonies they produce; the effect can be further softened by diluting the colours.
Colours known as ‘complementary’ face each other across the clock-face — orange-red and blue-green, for example, or pure yellow and violet. If you look at a strong colour for a while and then switch your eyes to white or a neutral colour, the complementary colour will then appear for a few seconds. Gertrude Jekyll, who in the early years of this century wrote the best book about the use of colour in the garden, believed that this apparition represented a natural longing for a totally different colour and she made great use of complementary colour associations in the flower borders she planned so skilfully. She also used contrasts when she wanted to please; the principles of colour association have not altered since her day.
However, though it is correct to regard harmonies as restful by comparison with contrasts, they vary a great deal among themselves. Harmonies based on the red, orange and yellow section of the colour circle can be very bright and exhilarating, whereas those in the red, violet to blue section are much quieter and those in the blue-green section are the most sober of all.
Green is a basic garden colour which can be associated with any of the others. But proceed with caution: leaf greens are much more varied, both in composition and in luminosity, than is generally realized. The very brightest greens tend, by competition, to tone down other luminous colours such as scarlet, yellow and orange whereas dark greens, such as those of yew and cherry laurel, tend to enhance the tones of contrasting colours.
You can also use colours in the garden to create illusions of distance. Very luminous colours, such as white and yellow, stand out so clearly, even when a long way off, that they often appear to be closer than they really are. Dark colours, and those of low luminosity in the purple and violet range, do the opposite, and exaggerate the distance between themselves and the viewer. Some colours are so alien to all the others that it is nearly impossible to assimilate them. This is one reason for using very bright reds with caution in Britain. Someone once referred to them as ‘burning holes in the landscape’.
Contrasts and harmonies of form are just as important as those of colour, but it is more difficult to codify them simply. Leaves may be large or small, rigid or soft, smooth-edged, jagged, lobed, fingered or composed of numerous separate leaflets arranged along a central mid-rib, a form botanists term pinnate They can also differ enormously in surface texture.
Not only are there many different greens in leaves, as well as blue-greys, silvery greys, purples, coppers and bronzes, there is an immense range of variegations, with white, cream, yellow and pink arranged in all manner of ways — speckled, blotched, veined and feathered.
Trees and shrubs vary enormously in habit, from spreading to narrowly erect, densely branched, open branched, angularly branched or ‘weeping’.
The best way to learn about plant associations is by observing them in well planned gardens and for this purpose there are few better ‘schools’ than Sissinghurst Castle, Kent; Great Dixter, Northiam, East Sussex; Cranborne, Dorset; Hidcote Manor, near Chipping Campden, Gloucestershire; Knightshayes Court, near Tiverton, Devon; and Crathes Castle, Banchory, Grampian.
Wherever you go you can pick up ideas, even from the simplest cottage or suburban garden. Genius in these matters is not confined to the great and in any case the most felicitous results are often more the result of luck than good management. Even when you know fairly precisely what you want, it is often difficult to get it quite right at the first attempt and adjustments may be necessary later in the light of what actually happens on the ground.