Which perennials will do best in my unusual soil?
Ann Elliot, Buckinghamshire
CHRISTINE SAYS You say you have 15cm of topsoil and beneath that, gravel. So before planting any new plants, incorporate lots of organic matter into the soil that has been taken out of the hole, then use this to refill the hole once the plants are in position. Plants that will do well in this situation include Lilium superbum, which produces maroon-spotted flowers in late summer to autumn on plants that grow to about 2m high. A lovely ground-hugger is Phlox adsurgens ‘Wagon Wheel’, which has trailing stems covered in pink flowers with petals that look like wheel spokes. Try trilliums such as T. grandiflorum, which produces white, three-petalled flowers, or T. erectum with deep red-purple blooms. They like organic matter, so keep them well mulched every year.