Green roofs are packed full of incredible benefits – they reduce GHG emissions, save on energy consumption and provide much needed urban habitation. But without the right plants and vegetation cover, none of these benefits would be applicable.
So we’ve picked the best plants for a green roof in a UK climate. Anything that thrives in largely damp, grey conditions (with the occasional week of sun in the summer) is high up our list.
How to choose the Best Green Roof Plants
Ultimately the:
- Size
- Durability
- Purpose – both aesthetic and otherwise
Of your green roof should dictate the best plants for it. If you’re new to this our guide(s) to building a DIY green roof would be a good starting point. And it’s worth checking out the type of green roof you’re looking for.
If you’re less concerned by reducing GHG emissions or your energy bills, but keen to get the pleasing aesthetic and wildlife benefits, you can focus on attractive wildflowers and sedums. Plants that have less impact on stability, stormwater management and your roof’s life expectancy.
They just look beautiful. And sometimes that’s all that matters.
But if you’re looking to build a green roof for the financial and environmental benefits, you’ll be better off focusing on hardier flora. Plants whose environmental benefits – generally – outweigh their aesthetics. And of course some lucky species have it all.
But we generally advocate a combination of the two. We want roofs that brighten up urban spaces whilst reducing our impact on the planet. And you can do both.
9 Best Green Roof Plants for Extensive Roofs
Most people looking to build a DIY green roof go for a lower maintenance extensive green roof. And whilst extensive roofs are cheaper and more self-sufficient, there are limitations on what plants can survive and thrive based on:
- How much substrate they need. Extensive roofs are lighter and hold less soil than their intensive green roof counterparts.
- You can find the best living roof substrates here.
- Size. Extensive roofs can’t support huge plants due to the lighter-weight nature of their infrastructure
- Maintenance. You want plants that don’t require much watering as extensive roofs aren’t generally accessible.
Plant | Family | Key Feature | Cost |
|---|---|---|---|
Gold Sedum | Sedum | Incredibly hardy, drought tolerant perennial | £ |
White Stonecrop | Sedum | Creates a lightweight, sprawling cover on a roof | £ |
Widow’s Cross | Sedum | Very hardy. Can survive almost any weather conditions. | £ |
Two Row Stonecrop | Sedum | Very hardy. Can survive almost any weather conditions. | £ |
Birdsfoot Trefoil | Pea | Perennial plant that attracts bees | £ |
Sempervivums | Evergreen | Hardy, low maintenance plants that can grow between rocks | £ |
Oregano | Mint | Aesthetically beautiful, cooking (obviously) and perennial | £ |
Aenoium Arboreum | Evergreen | Hardy, survives in minimal soil and can tolerate shade | ££ |
Aster Alpinus | Asteracae | Hardy, perennial wildflower | ££ |
Obviously these plants would work on an intensive roof too. But you can afford to be a little more extravagant.
Gold Sedum
Gold sedum – gold moss or sedum acre – is an incredibly hardy, drought tolerant evergreen perennial that forms a mat of bright, beautiful yellow flowers.
An incredibly low maintenance sedum that grows well in dry – medium, moderately fertile soil. Perfect for lazy gardeners.
- £14.47
- 500 seeds
- Delivery time usually around a week
White Stonecrop
White stonecrop – sedum album – is a herbaceous perennial with a sprawling growth habit. Perfect for spreading a lightweight covering on a rooftop.
An individual plant won’t spread more than two feet and, like most sedums, it’s particularly hardy. It’s pretty white flowers are very attractive to pollinators. Ideal for encouraging wildlife habitation.
Bright green in nature until the Autumn, when the green leaves transition to a reddish-brown colour. Hence the name coral carpet. It’ll tolerate almost any kind of soil, but does better in the sharp-drained variety, only requiring very occasional, substantial watering.
- £10.99
- 5000 seeds
Widow's Cross
Widow’s Cross is an annual (or evergreen) perennial with attractive pink and light green stems. A larger sedum that can rise to a foot in height, it provides some much needed vertical variation to your living roof without significantly increasing the weight.
Like most sedums it’s very hardy and requires little maintenance, growing well in generally dry, lower quality soil. Although they do prefer full sun exposure.
- £13.99
- 50+ seeds
Two Row Stonecrop
Two Row Stonecrop – Sedum Spurium – is a mat forming sedum that creates a carpet of reddish hued flowers in the later summer months.
Soil-wise they grow best in moderately fertile, well-drained soil in full sunlight.
On the smaller size height wise – only growing to around 6 inches – this low maintenance, low weight sedum creates a burgundy coloured ground cover. A perfect lightweight mat cover for a rooftop.
- £13.99
- 100 seeds
Birdsfoot Trefoil
A member of the pea family with beautiful yellow, slipper-like flowers, Birdsfoot Trefoil can add a nice element of vertical variation to your roof, as it grows upwards of 12 inches.
The rich, egg-yolk yellow flowers lend themselves to evocative nicknames such as ‘eggs and bacon‘ and ‘hen and chickens.’
This generally low-creeping perennial plant is a valuable source of food for a number of pollinating insects. Perfect for biodiverse, or wildlife focused extensive roofs.
- £5.76
- 10g (c. 100 seeds)
Sempervivums
Sempervivums – houseleeks – are hardy, alpine plants whose name literally translates as always alive. A reference to their tolerance to extreme temperatures and droughts.
And really this is what makes sempervivums so perfect for living roofs. Their ability to survive the winter months, lightweight nature and lack of maintenance make these gorgeous succulents green roof essentials.
Dry, low fertile soil help these low-growing plants thrive. So if your roof is well-drained and in full sun, sempervivums are a must-have.
- £34.99
- Collection of 30 plug plants
- Each plug is 35mm x 50mm
Oregano
Oregano is a lightweight, perennial herb that thrives in direct sunlight.
It’s pretty rose-purple or white flowers fit perfectly onto a green roof and they thrive in direct sunlight. So if your roof is primarily shaded, oregano won’t thrive.
You will need to trim oregano as it reaches around 4 inches in height. This encourages bushier growth and prevents it reaching for the sunlight.
Ultimately oregano is a hardy, pretty little plant that requires a little maintenance, but, like most herbs, is relatively self-sufficient.
- £6.50
- 3 x medium plug plants
- Perfect for slotting into a newly formed green roof
Aenoium Arboreum
Aenoium Arboreum – dark purple houseleek tree – are evergreen succulents with succulent, fleshy leaves that can grow up to 1.5m in height.
So you’d need to be confident in your green roof’s stability as it’s a much larger, heavier plant.
If grown in full sunlight (a must for maximising growth and quality) the foliage turns such a dark purple, it almost looks black. An incredibly dramatic tree.
Soil-wise it’s best grown in dry – medium moisture, well-drained soil. And whilst they’re (sort of) drought tolerant, they need more consistent watering than other succulents as they have a shallow root system
But this is what makes them perfect for green roofs.
- £14.47
- 100 seeds
Aster Alpinus
Aster Alpinus – Alpine Aster – is a perennial flower that thrives in full sun and well-drained, low moisture soil.
Because of their alpine nature, they’re incredibly hardy plants with beautiful flowers. Daisy-like in nature.
So if your roof gets full sunlight, drains well and doesn’t have particularly high quality soil (but you’re in desperate need of a little colour) then Aster Alpinus is an excellent option.
- £3.20
- 10 seeds
Best Grass for a Green Roof
Grass’s hardy nature, vertical variation and ability to attract pollinators and create habitation for wildlife make them the perfect accompaniment to a green roof project. Here are a couple of our favourites.
Carex Nigra
Carex Nigra – black sedge – is a strikingly black grass that stands around 40-50cm tall. Again, a lovely bit of vertical variation on a green roof.
You’ll thank us when you see it. Especially as it provides welcome shelter for wildlife.
This perennial plant generally favours wet conditions. generally more associated with wetlands. So if your soil type is dry – and the rest of the plants you have grow best in dryer conditions – it’s probably not the friendliest mix.
Albeit a beautiful grass.
- 1kg of seeds
- Approx 1000 seeds / g
Carex Flacca
Carex Flacca – Blue Sedge – is a slow-creeping, evergreen sedge that stands around the same height as Carex Nigra. 40-50cm.
It can spread really quickly – in some cases this makes it absolutely perfect for a green roof. It does mean you may need to pay slightly closer attention to maintenance.
But it’s bright green leaves and blueish fronds form a picturesque ground cover. They generally thrive in medium – wet soil, but are pretty adaptable and – like most grasses – are drought tolerant.
- £15.99
- 2 x plug plants
- c. 20cm expected height
Green Roof Plant FAQs
What can I plant on a Green Roof?
It completely depends on the type of green roof you have.
Extensive green roofs are much more lightweight and focus more on the environmental benefits. Intensive roofs can be fully interactive gardens.
As such intensive roofs can accommodate almost any plant or tree. Extensive roofs – by far the most common – tend to use smaller, lower maintenance plants like succulents, sedges and small shrubs or trees.
How often do I need to Water the Plants?
Again this also depends on the type of roof you have, the climate and the types of plants.
But generally extensive roofs are low maintenance and only require watering a few times a year. Sedges and succulents are very low maintenance, drought-tolerant plants.
However if you have larger, more intensive plants and foliage, you may need to water more frequently. Especially at the beginning of the roof and plants lifecycle to help them bed in.
How much weight can a Green Roof support?
Intensive roofs have been known to support upwards of 500kg / m².
Extensive roofs wouldn’t weigh anymore than 150kg / m². And even that is pushing it. Most extensive green roofs won’t weight more than 60kg / m².
But as always it’s worth checking with a professional if you’re unsure. Ultimately this is the only part of a DIY green roof where we absolutely recommend professional assistance.
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