It's all in the mix - Diarmuid Gavin's top tips for a magical border

Indulge your inner artist by creating a colourful, magical mixed border with my top tips

Geranium Rozanne

Diarmuid Gavin

Last week I gazed at the emerging perennials at the herbaceous border in Powerscourt Estate Gardens in Enniskerry, Co Wicklow. In many ways it's the archetypal vision of a beautiful garden - wide beds soon to be packed with a kaleidoscope of tasteful colours. Gertrude Jekyll is most associated with this type of gardening. Originally an artist, she applied her knowledge of colour to great effect in planning her famous borders.

Today, most of our gardens aren't big enough, and we don't have armies of gardeners to maintain borders that require endless feeding, weeding and staking. The contemporary answer is the mixed border: a combination of herbaceous planting alongside evergreen and deciduous shrubs, annuals and bulbs. It's a good time of year to plan and plant, so here's what to consider.

PLAN: Location is first. If you have a nice, open, sunny position, that will be ideal. If you have a shady garden, that will determine your plant choice. Dig the soil over to remove any weeds, and add compost or well-rotted manure. Will you have a colour theme? Gertrude Jekyll liked to run colours, from cool whites and blues merging eventually with warmer pinks to hot reds and oranges. Vita Sackville-West's creation at Sissinghurst is famously all white, while Helen Dillon in Ranelagh, Dublin, separates hot and cool.

You want to create different shapes, through a mixture of shrubs - evergreen and deciduous - small trees such as Japanese maple, and your perennial plants. This will be the backbone of your border, providing structure and substance all year long. Examples here are box, skimmia, hydrangeas, phormium, azaleas, rosemary and bay trees.

Consider the different textures: soft feathery plumes of grasses; strong shapes like hosta leaves; the jagged serrations of melianthus; architectural acanthus leaves, and frothy fern fronds. Try to incorporate different flower shapes: globes of alliums; daisy- like coreopsis, anthemis and rudbeckia; spikes of veronica, and bell-shaped foxgloves and campanulas. Different heights will create a rhythm in your border: tall spires of ligularia, lobelia, red hot poker, foxtail lilies and white willow herb contrast beautifully with softer mounds of hardy geraniums, Alchemilla mollis and lavender. Don't forget about late summer… sedums, leucanthemums, penstemons and crocosmias will all extend your colour season.

PLANT: When you've made your final selection, the golden rule is to plant in uneven numbers - groups of three or five of the same plant always create the most pleasing effect on the eye. Repeat planting of the same species at another position in the border, even several times, will create unity. Find out how big the plant will become and give it sufficient room to do so. Gaps can be temporarily filled with your favourite bedding plants and annuals.

My border stars

Geranium ‘Rozanne’ (pictured): Once voted Plant of the Centenary at the Chelsea Flower Show, it’s a sterile hybrid so it won’t invest energy into producing seed, just into flowering right through the summer into autumn. Its purple/blue flowers are still attractive to bees.

Nepeta ‘Six Hills Giant’: Catnip or catmint

(cats love this plant!). Very long season of flowering from June to October, producing small lavender-blue blossoms. This is great plant for edging borders and pathways — it grows like wildfire, and its crushed foliage smells of mint.

Thalictrum delavayi ‘Splendide’: Meadow rue is a very beautiful and delicate perennial with dainty mauve flowers atop tall stems throughout the summer. I’m pairing this with yellow hemerocallis, which they will tower above.

Melianthus major: Strictly speaking, this is a shrub but behaves like a perennial in our climate and will need some winter protection in harsher areas. Wonderful serrated silvery foliage — a prize specimen.