Lucy's 'Cosmic love' dahlia collection

Dahlia tubers can be planted outside after frost, or started off in pots under glass in late winter to early spring. Plant them horizontally approximately 12cm (5in) deep, making sure the ‘eyes’ are uppermost. Allow enough room between each tuber so the plants can grow and spread to their full size being over-crowded.

Potted plants should be protected from frost in a well-lit location such as a frost-free greenhouse, cold porch, or cold-frame. Gradually acclimatise (harden-off) in mid-late spring before planting out into borders, protecting from late frosts with cloches or horticultural fleece.

While in growth, provide a high-nitrogen liquid feed each week in June, then a high-potash fertiliser each week from July to September. Stake with canes or brushwood if it becomes necessary. In mild areas, leave them in situ over winter, but protect the crown with a generous layer of dry mulch.

In colder areas, carefully lift and clean the tubers once the first frosts have blackened the foliage and allow them to dry naturally indoors. Then place the dry tubers in a shallow tray, just covered with slightly moist potting compost, sand or vermiculite and store in a frost-free place until planting out again.