Chrysanthemums — bright, fragrant and forgiving — can turn a bare roof into a garden. They come in yellow, white, red and pink, grow easily, ask for little care, freshen the air and, in some varieties, carry medicinal value.

• The pot: clay or ceramic, with drainage holes.
• The soil: loam mixed with rotted cow dung or compost, moisture-holding but airy.
• The plant: good seedlings or seed, spaced well apart in pots or beds.
• Water: chrysanthemums dislike wet feet; water lightly when the soil feels dry.
• Feed: a liquid organic fertiliser once a month, with extra potash and phosphate as buds form.
• Sun: at least five to six hours of direct sunlight a day.
• Pruning: remove dead leaves and stems; cut back every two months for new growth.

• Make a pattern of colours in one corner.
• Stagger pots by height, tall at the back.
• Ring a sitting-out place with flowers.
• Add LED lighting for the evenings.

A little care and a little planning, and the roof becomes a green, coloured refuge — good for the eye and for the mind.

Photo: Chrysanthemum × morifolium — Shuvaev / Wikimedia Commons (CC BY-SA 4.0)