Whatever kind of green roof you have there is no excuse for a drab autumn. After a couple of years’ observation, I conclude that my top 4 skyplugs for late season colour can, between them, perk up any style of green roof.
Delosperma cooperii – I’ve said many times and will repeat again, I can’t understand why this plant is not included in standard sedum roofs. Big, bright purple flowers will last as long as they have a little sun. This succulent works in the same way as sedums and does not tolerate much shade.
Lychnis flos-cuculi – this classic wildflower is at home on any biodiverse or meadow style roof, and can flower at unusual times depending on yearly temperature variations. It is recommended by both Natural England and RHS ‘perfect for pollinators’ lists, and maybe the provision of nectar at times when other plants are dormant makes it even more valuable to hungry insects.
Trifolium pratense – also feeds a wide range of insects and is therefore great to support wildlife preparing for the winter. Unlike many wildflowers that require slightly higher nutrition or ‘semi-intensive’ substrates, clovers can thrive in ultra-low extensive substrates designed for sedums. They fix their own nitrogen which means they can grow and flower very quickly, but given too much space and nutrition they will need maintenance to keep them at bay.
Dianthus gratianopolitanus – although Dianthus carthusianorum is also excellent, this one keeps beating it for late flowering on my office roofs. D. gratianopolitanus has a shorter stem and therefore fits in well with low growing alpine schemes, whereas D. carthusianorum’s long slender stems can give a little more height and interest to an alpine roof or can fit in well amongst taller wildflowers.
Whatever your green roof style, it makes sense to keep it looking exciting for as long as possible!