Green Roofs for Bees

Since becoming a beekeeper I’m acutely conscious of the number of opportunities to help our pollinators we, as a society miss. We’re super-keen to remove ivy from walls and trees – even though ivy flowers are one of the best sources of pollen and nectar for autumn-flying bees. We’re still paving over gardens to make less work and more parking space. We’re also building homes, retail parks, offices etc with less green spaces.

bee on green roof plant

Bees are incredibly important to our economy, food production and biodiversity. As their habitat is swallowed up by towns and developers, could green roofing be the answer to preserving bee populations?

All that new development means that wildlife habitat is in danger of becoming fragmented, particularly in our cities. Instead of joined up green spaces with soil for nesting and plants for foraging, bees (and other insects) have to travel between islands of habitat.

With so many benefits attached to green roofs other than wildlife benefits, perhaps we should all be striving to add a living roof to whatever surface we can. (Benefits of green roofing include insulation, flood amelioration, noise abatement, air quality and protection for waterproofing).

Some cities are acknowledging the need to join up these “habitat patches” in order to support wildlife. And indeed, to promote wellbeing amongst human inhabitants and visitors. Who wouldn’t prefer to walk along tree lined streets where flowers bloom in planters, birds sing and butterflies flutter by?

Join up the gaps between parks and gardens

Green roofs offer a fantastic way to create vegetative “stepping stones” between parks and gardens.

typical urban roofscape with relatively little bee fodder

A bees-eye view of a city. The potential here for increasing habitat is quite large. Provided these buildings are sturdy enough, they could support living roofs.

A living green roof doesn’t need to impinge on human life at all. It’s up out of the way, you can still park your car beneath a green roof car-port. You can store bins, bikes and buggies in a green roof shelter. You can cook just as well in a kitchen extension with a living roof. In fact, if you have upstairs windows, you get a better view and a sense of wellbeing from looking onto plants instead of bare waterproofing.

What do bees need from a green roof?

There are more species of bee than you can imagine living in our cities. We all know the honeybee of course, they live in hives that are carefully positioned by beekeepers. But what of the bumblebees and solitary bees that nest in soil? Honeybees often receive supplementary feed when forage is in short supply. Wild bees rely entirely on what they can find locally.

Green roofs have the potential to provide nest sites AND forage for bees.

Which plants are best for bees?

Bees need two things from their food source. Pollen and nectar. Pollen is high in protein and is fed to bee larvae to help them develop. Nectar is an energy drink. It’s nectar that the honey bees store as honey.

Native flowering plants such as those found in Meadowmat Roof and Garden Mix or Meadowmat for Birds and Bees are just awesome. By planting a mixture of flowering plants you are offering bees a varied diet over a long period of time.

Some non-native plants, such as sedums are also a big favourite with bees. They’re incredibly nectar-rich and the shape of the flower allows bees easy access to the valuable energy drink.

Tiny green roof on a bird feeding table

A green roof doesn't need to be enormous to be effective. A sedum topped bird table like this one could fit on a balcony and still be found - and used - by foraging bees.

Which plants are best for green roofs?

The skill in designing a green roof for bees is in finding a balance between the plant species and the suitability of the building itself.

Let’s think about wildflowers for a moment. The average wild flower roof needs 15cm of growing medium in order for the plants to thrive. That puts quite a lot of strain on a building because it’s heavy. Around 250Kg per square meter. Not many garden sheds or bin stores can cope with the loading.

A sedum roof weighs considerably less than a wildflower roof. If it is created using Enviromat sedum matting it can exert as little as 42Kg per square metre loading on the roof. Bear in mind though that you should also factor in what architects call “live loading”. So work on 120Kg per square metre to allow leeway for snow and for maintenance people working on the roof.

A mix of sedum plants offers a nice long flowering period too. In the case of Enviromat, you can expect to see flowers from April-October, which is when bees are most active.

 

More information on green roofs

How green roofs benefit wildlife

Download our FREE green roof design guide

Green roofs for healthy cities – international organisation researching and promoting the benefits of green roofs

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