Much attention is given to the Bee Hotels you can attach to your garden wall or fence that are typically wooden boxes filled with hollow tubes and plant stems. And very good they are, too, with a very high chance of success if the holes are the right size (about 2–10mm diameter) and the box is put in a sunny sheltered location at about chest height.
What isn't so widely known is that they only provide nesting chambers for a relatively small number of the 220 or so solitary bee species found in the UK. Many species actually require quite a different home, and one of the best habitats to find lots of types of mining bee is bare, warm banks of sandy soil that they can burrow into.
However, as Marc Carlton explains in what are my 'go to' webpages for gardening for pollinators, gardeners tend to overlook such habitats, and "advice that encourages you to dig soil, or to mulch it, or to grow ground-cover plants, means that there is often little habitat for mining bees in gardens".
So when I was helping our Pagham Harbour nature reserve team devise their enlarged and much improved Discovery Area, I challenged them to include a Bee Bank.
However, it was over to the reserve team to actually turn the idea into reality, and the warden, Barry O'Dowd, enthusiastically took on the challenge of coming up with a design.
With little advice out there on how to go about it, Barry based his plans on what was done by the Friends of Rawcliffe Meadows in York, added some of his own creativity, and then turned to the gallant team of RSPB volunteers to build it.
There was no source of sandy material nearby, or the use of a digger, so subsoil had to be bought in to build the embankments before they were covered with sand.
In the centre of the bank, the team created two wooden bays to contain sandy material, one large, one small. They were constructed with recycled timber from old pond dipping platforms, and are effectively open-fronted 'boxes' made using 6” x 6” uprights and 6”x 2” horizontals. There is no cement base, just a sand and gravel mix. In retrospect the structures didn’t need to be so deep from front to back (it took many tons of material).
The back half of the big one was filled with ballast (sand and gravel mix) and the front half was layered with builders sand (pink and yellow). By placing a plank in front of the 'open box' as material was added ('shuttering' I believe is the term), a vertical face of sandy material could be built up.
Most layers are 20 parts sand to one part cement. The cement mix keeps the sand in place and on the lower layers a 10:1 mix was used to deter rabbits digging. Some layers have a little soil mixed in for variety. The outside bank has 2–3 inches of sand over it and on the steeper front face this is again a 1:20 mix with cement.
Also the team dug up some clay on the reserve, moistened it and mixed in some straw. This added to the variety of substrates on the vertical front face. In wet weather it does get a bit soggy, but in the summer it developed some nice cracks.
The large bank has a green roof. This is made of 18mm marine ply, with 3" square treated softwood sides. It is lined with pond liner on the base of the roof and includes five layers of pond felt to hold some moisture. This was raised on a sloping strip of wood to allow water to run off. Then a 2–3" deep layer of light green roof soil was added, which is £5 a sack from www.greenroofsubstrates.co.uk. This has been sown with a native green roof flora mix and also some plug plants of native sedum etc. The smaller bank has a deep sand roof (6") for wasps to bury down into.
The team also added sandy banks either side of the main 'cliff faces' and added some drilled logs for extra variety. On the outside front sides of the wooden structures it was difficult to keep the sand bank steep so the team used logs to form a structure and drilled holes for invertebrates.
Here is the finished construction, fenced off from rabbits with the back slope and ground in front sown with a wild flower and grass mix.
And what a good time it looks like the team had building it.
Even though construction took place over the summer, some small wasps and bees have already used the sand banks, including some black spider-hunting wasps which took up residence using cracks on the edges of the sand faces to burrow into.
I look forward to checking in with the team in summer 2019 to find out what has moved in - it should be fascinating, and I am already planning my own Bee Bank. And if you want to see the bank, and all the other wonders of RSPB Pagham Harbour (West Sussex), the Discovery Area is open daily and is just a 2-minute walk from the visitor centre - the team will be delighted to see you.
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