PLANT YOUR BORDER
Most of these plants do best on moistureretentive soil, except for the scabious that overwinters badly in cold and wet, so grow it as an annual. Clear weeds, break up compacted ground and spread plenty of well-rotted manure across the border this autumn then leave the worms to gradually pull it into the soil before planting next spring. In future years, mulch annually with well-rotted organic matter to reduce weeds and replenish soil.
1 Order dahlias and cosmos
Order dahlia and cosmos tubers early and once they arrive in March pot up in good multipurpose compost. Grow on in a frost-free greenhouse or on a sunny windowsill in the house. Their young shoots can be used as basal cuttings, giving you extra plants for free.
2 Sow the rudbeckia and scabious
Brightly coloured R. hirta cultivars are short-lived perennials that can be grown as annuals. If you sow them early enough they’ll flower in their first year. In March sow them in pots or trays indoors, on the surface of fresh seed compost. Seedlings can be a little slow in their early stages but eventually get into their stride. Scabiosa atropurpurea prefers a well-drained soil and sheltered site and can rot in heavy clay soil over winter. The alternative is to grow them as annuals, sowing under cover in or direct outside in March and April. Or, buy trays of young plants in late spring.
3 Plant out after frost
Buy in young plants of Rudbeckia fulgida sullivantii ‘Goldsturm’ and Lobelia cardinalis ‘Queen Victoria’ but avoid planting when the ground is frozen or waterlogged. Harden off the dahlias, cosmos, Rudbeckia hirta and scabious. Start with the lobelia, adding additional well-rotted organic matter to the planting hole to maximise the soil’s moisture-retaining properties – this plant even grows along the margins of a pond. Then add the perennial rudbeckia – neither of these plants needs staking. After all risk of frost, plant out the Rudbeckia hirta, scabious, dahlias and cosmos, improving each planting hole and mulching to finish. Short dahlia cultivars such as ‘Moonfire’ need little support but a single low cane and some craftily looped twine can help to keep things secure. Watch out for slugs and snails feasting on the new shoots and keep plants growing smoothly by watering during dry spells and deadheading or cutting for the house regularly to keep the flowers coming from July into autumn.
4 Help them through the winter
Towards the end of the season, leave rudbeckia flowerheads intact to catch the first frosts. The perennial rudbeckias and lobelia should bulk up relatively quickly so lift and split every couple of years to keep them growing vigorously. In more sheltered parts of the country, it’s worth leaving the rest of the plants in the ground with a layer of dry mulch for protection. They may reappear the following spring, especially if there’s a mild winter and you’re on well-drained soil. Alternatively, dig up the dahlias and cosmos and store in barely damp potting compost in a frost-free shed. Label plants as you lift to help identify them.