How to chill out with cool plant colours

Cool colours (greens, blues and whites) are deemed calming, while hot colours (reds, oranges and yellows) are seen as exhilarating. Research studies tend to bear this out when it comes to flower and foliage colour. Cool colours are relaxing and create harmony in a planting composition. Sometimes less is more, and limiting yourself to two or three colours can provide better synergy and bring out the subtle effects of individual plants more effectively.  

If you have a semi-shady corner in the garden, or want to cover an unsightly wall or shed, consider planting a mix of small trees, shrubs, herbaceous plants and annuals to create a harmonious effect with cool colours. If you have a lightly shaded spot, choose one of the green Japanese maples (Acer palmatum). The types with dissected leaves, such as “Emerald Lace”, have a refined, dainty appeal.

Hydrangea paniculata

To provide a little contrast through a bolder, stronger leaf shape you might add Hydrangea paniculata “Limelight”, with its large plumes of pale lime-green flowers maturing over time to white and sometimes pink. In a similar vein is Viburnum opulus “Roseum”, with its balls of sterile flowers in pale green or cream.

Consider planting one of the mock oranges (such as “Beauclerk”) to add to the white floral theme, but also bring the luscious scent of orange to the mix. For a delicate late summer effect, Fuchsia “Hawkshead” has simple white bell-like flowers. Ivy can be used to screen a wall, and here Hedera hibernica “Hamilton” stands out with its distinctive leaf shape, providing an attractive mid-green facade.  

Herbaceous plants can be dispersed among the shrubs, or positioned slightly in front to take centre stage when they flower. Continuing the white theme, you can achieve early flowers with the Christmas rose (Helleborus niger) in late winter and the pheasant’s-eye daffodil (Narcissus poeticus) in spring.

Dicentra spectabilis “Alba” provides an arch of heart-shaped flowers in early summer, and this can be followed by Phlox paniculata “White Admiral” and Physostegia virginiana “Alba”. (“Alba” means white, so you will come across this word a lot when searching for white flowers.)

Maintain late summer interest with Anemone × hybrida “Honorine Jobert”, its anthers creating an amber wheel at the heart of each flower, which is reminiscent of the pheasant’s-eye daffodil. Bold-textured Hosta provide ground cover throughout the growing season and add to the relaxing mantle of green.

Veronica spicata

White and green alone are both dramatic and soothing, but blue can be added for a different effect. Veronica spicata “Royal Candles”, with its deep-blue spires, will do well in a more open position near the front of the border. Jacob’s ladder (Polemonium caeruleum) has a mauve-blue flower and fern-like foliage, while Tradescantia virginiana "Blue ’n’ Gold” throws up strap-like green-gold leaves set off with blue button flowers.

Finally for the perennials, I would squeeze in Aquilegia coerulea (or caerulea), from the Rocky Mountains, for its blue-and-white flowers.

If there is any space left, add some annuals and biennials. In fact, even if there isn’t any space, placing a few pots in front of the border gives you an excuse to grow more plants and provides additional summer interest. The star-white flowers of the white Beacon Impatiens (busy Lizzie) will simply glow out from a background of deep-green foliage.

White snapdragons, such as Antirrhinum “Sonnet White”, have a fresh appeal, and Nicotiana Cuba strain comes in pure-white or lime-green flowers, so either will fit into the scheme. The flowers on the foxglove Digitalis “Pam’s Split” are not pure white, having a deep-purple centre, but this is not intrusive enough for us to exclude it from the mix.

For the blues we have the classic Lobelia; L. erinus “Crystal Palace” is deep blue, and although L.e. “Cambridge Blue” is not Cambridge blue at all, it is a very attractive denim-blue, and warrants its place on that basis. A plant that prefers a bit more sun is Nigella damascena “Moody Blues”, but I would take the chance and include it here.

If you want the best of both worlds, the amusingly named Viola hybrida “Sorbet Yesterday Today & Tomorrow” has flowers that come out white but after two or three days turn mid-blue. It’s fairly uncommon—and thus spectacular—to see a variety of hues all on the same plant.

Extracted from How Plants Can Save Your Life by Dr Ross Cameron (Greenfinch) 

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