PLANT YOUR BORDER
All these plants prefer a sunny site, so pick somewhere with no more than partial shade. A fertile but well-drained soil will give the best display, although there’s a bit of a balancing act here because the agastache, verbena and artemisia must have good drainage over winter, while the dahlias and lobelia want enough moisture to power their summer growth. Therefore, add plenty of well-rotted organic matter, which both opens up the soil structure and holds onto moisture. Take care to deal with any perennial weeds before you start.
Start with the dahlias
Order dahlia tubers early from a specialist supplier to be sure of good quality plants. Pot up in a bright, frost-free place in early spring using multipurpose compost, keeping an eye out for slugs. Take cuttings from a couple of shoots and you’ll have extra plants for free. Plant out after all risk of frost, improving the planting hole with compost and stake taller cultivars. Deadhead every couple of days in summer and water in dry spells.
Once the foliage has been blackened by frost, dig up and overwinter tubers in barely damp compost in a frost-free shed. If you’re in a sheltered part of the country and have well-drained soil, you can try leaving them in the ground with a protective mulch laid over the top. Apart from prolonged winter wet, the biggest threat is slugs and snails damaging the new shoots in spring.