Kim Wilde answers your gardening questions.
I have tried to grow Chinese lanterns from seed and from roots, but with no success. What's the secret?
I love the orange lanterns of this decorative plant, but Physalis alkekengi, a member of the nightshade family, is poisonous - especially the leaves and unripe berries. The ripe berries are edible but very sour. This hardy perennial from Brazil will grow happily in well-drained, sandy soil that's not too rich. It is usually easy to grow from seed, sown indoors in March. Seedlings can be initially thinned out, then grown on in 9cm pots and planted out after hardening off some time in June. Taking root cuttings during the dormant season (November to March) will usually give good results. Lift the plant and cut some healthy roots into 5cm lengths, lay them flat in a seed tray and cover with 2cm of compost. Chinese lanterns grow well in dappled sunlight and make effective groundcover, although slugs love them.
I have an area that is perfect for a roof garden. How do I plan one, and what plants can I grow?
Roof gardens present several challenges, including extremes of temperature caused by exposure to wind and sun. The load-bearing capacity of walls and floors needs to be appraised to make sure that they can take the weight of containers as well as people. You will probably find an area for storage useful, and an outside tap for a watering system should be considered as soil can easily dry out. And don't forget lighting. As for plants, choose ones described as good for windy or coastal areas such as Escallonia rubra var. macrantha, Griselinia littoralis and Olearia x haastii - all effective evergreen screening plants. Bamboo makes an elegant screen, as well as a lovely rustling sound, which is useful for masking the noise of traffic. Pseudosasa japonica is more tolerant to windy and exposed conditions than some bamboos, and can tolerate full sun to deep shade. Hedera hibernica will reliably form a dense, evergreen climbing screen for privacy, and could be combined with the beautifully scented Trachelospermum jasminoides (also evergreen).