Colour-wheel gardening is the art of putting together colour schemes [through plants] that achieve classical harmonies and contrasts according to the relationship of individual colours on the wheel.

At the heart of the wheel are the three primary colours (red, yellow and blue), three secondary colours (green, orange and purple) and six tertiary colours created by mixing primary and secondary colours to get yellow-orange, red-orange, red-purple, blue-purple, blue-green and yellow-green.

In colour-wheel gardening, you achieve the greatest harmonies when you put flowers together that are next to each other on the typical 12-part wheel.

These are called analogous colours and usually any three colours that are side by side, such as yellow-green, yellow and yellow-orange, are eye-pleasing and evoke a sense of natural harmony.

Colours opposite each other on the wheel, such as orange and blue, red and green, are considered complementary and have a vibrant, high-contrast impact when planted together.

In the garden, blue and orange flowers can make a stunning combination and also have an interesting intensifying effect on each other -- blue strengthens orange and vice-versa. Silver, white, black and grey are considered neutral colours that can be mixed with any of the others.

How does all this translate into your planting schemes? Well, many gardeners get so frustrated with colour clashes, they decide to simply group all their warm colours together (reds, yellows and oranges) and all of their cool colours together (blues, purples and greens). However, this not only takes some of the fun out of gardening, it can reduce borders to boring monochromatic schemes.

A simple solution is to put together any three colours that are an equi-distance from each other on the wheel. Or you can achieve lovely results by sticking to same-side colours, warm or cool, by choosing three colours on the same side but allowing one or two to be more dominant such as yellow, green and blue.

Nature has one clever trick of bringing harmony to any scheme: Put lots of green between everything as a natural buffer. This always seems to work. If you want to try your hand at colour-wheel gardening, here are some great plants in specific colour categories.

Gorgeous greens

• Euphorbia characias wulfenii
• Achemilla mollis (lady's mantle)
• Adiantum pedatum (maidenhair fern)
• Albitzia julibrissen
• Hosta Canadian Shield

Passionate purples

• Clematis jackmanii
• Echinacae purpurea Magnus
• Calicarpa bondinieri
• Pennisetum setaceum rubra (purple fountain grass)

Basic blacks

• Black mondo grass
• Ophiopogon planiscapus
• Nigrescens
• Viola Black Magic

Sensational silvers

• Artemisia Valerie Finnis
• Dichondra Silver Falls
• Stachys byzantina
• Euphorbia myrsinites

Beautiful blues

• Delphinium Pagan Blue
• Campanula persicifolia
• Clematis Rhapsody
• Geranium Rozeanne
• Hydrangea Blue Wave
• Iris sibirica
• Nigella damascena (Love in the Mist)
• Meconopsis betonicifolia (Himalayan blue poppy)

Juicy oranges

• Lonicera Mandarin
• Hemerocallis Orange Crush
• Potentilla William Rollison
• Rudbeckia Indian Summer
• Zinnia Profusion Orange

Pretty pinks

• Rosa Pink Peace
• Hydrangea Claudie
• Lavatera Barnsley
• Rosa The Fairy
• Nicotiana Bright Pink
• Paeonia Bowl of Beauty

Brilliant whites

• Styachs japonicus
• Choiysa ternata
• Hosta plantaginea
• Hydrangea paniculata
• Lilium Casa Blanca
• Clematis Snowdrift
• Magnolia seiboldii
• Philadelphus coronaria
• Romneya coulteri

Mellow yellows

• Hellenium
• Brugmansia
• Carex Evergold
• Hakonecloa macra Aureola
• Hemerocallis Stella de Oro
• Coreopsis Moonbean
• Magnolia Yellow Bird
• Rosa Graham Thomas
• Achillea (yarrow)

Ravishing reds

• Clematis Rouge Cardinal
• Dahlia Delta Red
• Hydrangea City of Paris
• Lychnis coronaria Blood Red
• Hollyhocks
• Monarda Grandview Scarlet
• Rosa Opening Night
• Salvia splendens