Biting Stonecrop

One of the sedums that make up the 'sedum mats’ widely flogged as ‘a green roof’. We have spent many years trying to lose this default planting and its accompanying thin soils and mats

Blue Flax

We nearly always include this in our seed mix for a roof, the hanging blue flowers and slender stems make this a wonderful sight during May.

Tradescantia

We found this on one of our container roofs; not sure what species it is but seems to be doing well. Although knocked back by the drought, it recovered each time and produces blue/purple flowers that seem to attract bees.  Probably best on soils 100mm + and light shade. One to try.

Quaking Grass

We don’t use many grasses within our initial planting, but this one is really good. It’s clump forming and spreads relatively slowly, so doesn’t compete for the moisture in the way other more vigorous species do.  It adds texture/shape and some denser cover for invertebrates, plus you get those droplet-like seedheads later in the year.

Wild Thyme

This is a must for your green roof. It will handle the heat even in soils down to 70mm, self seeds well, bees love it and smells great when you walk over it.  We have quite a few roofs that we visit simply to wander around, crushing the thyme, basil and marjoram – forget the flowers, go for the smell.

Bird’s Foot Trefoil

We’ve always associated this plant with sun-baked, very dry, shallow soils in which it happily survives in the wild. But the stress and high temperatures of a green roof test even this plant. Best grown in soils 120mm-180mm deep for it to do well.  In the right place its a great plant, good for bees and of course the food plant for seven native butterflies. Happy days.

Wild Chives

Very variable, but a great and some would say essential addition to a green roof. We use both the wild and culinary varieties on our roofs.  They make it through most droughts and can hang on in soils from 60mm deep. We really like the wild version as it varies in habit often with quite curly grey/green leaves.  It’s also more compact and tougher if walked over (Dusty take note!). As with virtually all the plants we use on our roofs, it’s great for bees and other pollinators.  It’s a green roof plant that’s naturally happy on shallow soils over rock – pretty much your average green roof conditions!

Orange Hawkweed or Fox and Cubs.

Not strictly native but widely naturalised.  A good greenroof plant, happy on soils 100mm + . Quite vigorous, we usually plant one reasonable clump on each roof. Great for bees, and if you’re like us, love orange!

Yellow Camomile

One of our favourite non natives for the roof. We always add this to the seed mix, it’s yellow flowers often dominate the roofs in the second and third years. Despite often growing over the whole roof, it doesn’t overpower its neighbours, and the flowers held up on single stems allow plenty of light and space for other plants. The foliage has a feathery grey/green colour contrasting with the bright yellow flowers. A must unless you have to keep to all natives.

Vipers Bugloss

Lots of nectar, and usually flowering June to September, when there is midsummer nectar gap and less forage for bees. A bi-annual, but it does seed back into the roof and has persisted on many of our roofs. Image: Derek Harper (creative commons sharealike)