Filling gaps in the dahlia border

Filling Gaps in the Dahlia Border

Let's explore how the plants you grow from seed can be used to fill gaps and bring a border to life, and how I use these to create successional interest that lasts over the whole growing season.

This bed at the front is the only bed where I grow hybrid dahlias that aren't from seed because passing people enjoy the colour. But I don't want it to be just dahlias, so I use other things to soften around the dahlias:

• lots of Alchemilla mollis, which is spreading and froths over onto the gravel
• annuals I've grown from seed, such as Nicotiana in white and lime green, and Cynoglossum 'Mystery Rose'

Perennials Grown from Seed Filling Out the Border

I've grown perennials from seed for this border, such as:

• Oenothera (previously Gaura) lindheimeri – very useful for softening the dahlias because it contrasts with the big blousy flowers of the dahlias
• Verbena bonariensis – really good for adding movement and airiness to a border and now self-seeds around
• Erysimum 'Apricot Twist' – first time I've grown it and will have beautiful coloured flowers.

Sequencing of Planting

I aim for a sequence of successional interest in this border throughout the season.

1. Early spring – tulips.
2. When tulips are over – dahlias go in mid-May.

• I either lift and keep tubers in the greenhouse or leave some in the border, mulched heavily.

1. Beds are quite bare then so I add in Nicotiana, Cynoglossum etc., which I've been raising in pots, in the gaps around the dahlias
2. The dahlias go on right into autumn; I then cut back and leave Verbena bonariensis to go to seed. The Oenothera (Gaura) and Erysimum I also leave until early spring, as they're a little tender and this gives them a better chance of surviving the winter.

• It's a good idea to leave slightly more tender things until spring as they then have more chance of surviving over winter.

Bringing the Border to Life with Annuals

This border goes from looking to bare to full within a few weeks in late May and June. Slotting annuals I've grown from seed into the border gives an instant fix of colour that you need at that time of year to bring the border to life.

Plant Directory

Alchemilla mollis

Lady's mantle

Herbaceous hardy perennial

Rosaceae

Cynoglossum 'Mystery Rose'

Chinese forget-me-not 'Mystery Rose'

Hardy annual or biennial

Boraginaceae

Dahlia hybrids

Hybrid dahlias

Tuberous tender perennials

Asteraceae

Erysimum 'Apricot Twist'

Wallflower 'Apricot Twist'

Evergreen hardy perennial

Brassicaceae

Gaura lindheimeri: now Oenothera lindheimeri

White gaura

Herbaceous hardy perennial

Onagraceae

Nicotiana 'Lime Green'

Tobacco flower 'Lime Green'

Short-lived tender perennial, grown as half-hardy annual

Solanaceae

Nicotiana alata 'White'

Tobacco flower 'White'

Short-lived tender perennial, grown as half-hardy annual

Solanaceae

Tulipa species and cultivars

Tulips

Bulbous hardy perennials

Liliaceae

Verbena bonariensis

Purple top

Herbaceous hardy perennial

Verbenaceae