Winter 2023

GREEN ROOFS
>>> Continued from page 14
Above: “Each 500mm x 500mm modular M-Tray sedum tray is packed with hardy plants carefully chosen to deliver the best coverage, year-round
interest, and an ‘all-you-can-eat’ buffet for bees and insects through the nectar in the flowers.”
important than ever to us to help
create sustainable environments for
pollinators, as their habitats come
under increasing pressure. When
you take into account that wildflower
meadows have declined by around 98%
in almost 100 years and the destruction
of habitats in pursuit of farming and
house-building have taken a huge toll
on natural habitats, no green roof is too
small or too big.
Sedum’s edge
We firmly believe that all green roofs –
wildflower and sedum – are brilliant at
supporting wildlife, from bees to bats,
butterflies to birds and a host of spiders
and other invertebrates, but sedum
definitely has the edge when it comes
to providing a highly nourishing food
source.
Each 500mm x 500mm modular
M-Tray sedum tray is packed with
hardy plants carefully chosen to deliver
the best coverage, year-round interest,
and an ‘all-you-can-eat’ buffet for
bees and insects through the nectar
in the flowers. Plants include sedum
species album, porchellum and caesars
gold. Wildflowers include forget-menots,
daisies, oregano, sea campion
and thrift. Native – and wild origin –
flowering species ensure maximum
diversity.
But increasing the number of green
roofs in urban areas should not
necessarily mean increasing the
number of bee hives; a key point that
often gets lost in the conversation is
ensuring that bees have sufficient food
to flourish. In cities, including London,
food can be scarce for hive-cultivated
honey bees, which are larger than
wild bees and have pollen appetites to
match. Hungry hive bees can crowd
out wild bees, so the challenge in urban
landscapes is to create more food
through more nectar rich flowers for all
bees.
To understand why wild bees are
important requires a dive into bee
behaviour. Some plants – including
blueberries, tomatoes, aubergines and
kiwis – need ‘buzz pollination’ which
honey bees can’t do. Bumblebees, which
only produce tiny quantities of honey,
can, vibrating their flight muscles to
dislodge pollen.
Bumblebees are also very good at
their job. A 1993 study found that
they could pollinate more flowers per
bee than honey bees. A study in 2001
reported that 250 female orchard
mason bees – neither a honey bee
nor a bumblebee – could pollinate an
acre of apple trees. In comparison,
their honey bee cousins required up
to 40,000 busy bodies to achieve the
same.
So while we may fete the honey bee, it’s
our wild bees that need protecting, and
we therefore need to be putting beefriendly
food sources back into towns
and cities – and that’s where green
roofs come in.
Contact
Wallbarn
T: 020 8916 2222
www.wallbarn.com
16 GREENSCAPE WINTER 2023 • www.greenscapemag.co.uk