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Encouraging nesting aculeates |
| The BWARS forum carried a useful discussion on
various ways to facilitate nesting aculeates on green roofs. This contained
many interesting suggestions that are applicable to most situations. The
discussion is reproduced below: |
Does anybody have advice on plants that provide
stem nesting resources please? I am trying
to find plants that will grow on green roofs that will provide nesting
resources. I am aware that
there are many species that nest in brambles, but they are not really the
kind of plant that you would ideally want to grow on a green roof.
Other advice on the best way to create other nesting resources (e.g. the
character of wood and masonry used by wood and masonry nesting spp., etc.)
will also be gratefully received.
Many thanks
Adam Bates |
There are many other rubus species that would
be O K for a green roof without being invasive. I don't see why raspberries
wouldn't work well. Any "pithy stemmed" plant are suitable for stem nesters.
Umbellifers would double up as great foraging plants then as nesting sites.
Timber for nest sites: The type of timber (from my experiences) doesn't seem
to matter all that much. They will utilise anything that has holes (there is
even a case of Megachile ligniseca using an iron tube!) OR if the timber is
of a sufficiently rotten state, then some will be able to create their own
nests.
I've used sycamore very effectively in my garden. The biggest issue is the
positioning of the nest post. It took me two years of fiddling to get the
best spot but now is inundated with Osmias and Anthidium. Like most nesting
sites choose the sunniest spot in a sheltered position.
Angle the post south and make sure the post is drilled with many holes of
different sizes. A 6 - 8mm hole seems to be the most productive in my posts.
I have a range of 3mm to 10mm. Of course the usage of different hole sizes
will change depending on where you are in the country and the foraging
provisions of the green roof. Don't forget about the provisioning of
suitable forage plants on the roof (for the location) to attract the bees
in.
Andy Jukes |
That is really helpfull thanks. How deep do the
holes need to be, or is a good range of depths
helpfull again? I will have a good think about suitable pithy stemmed plants
that will survive the conditions. Do the stems need to be dead in order to
be utilised? In which case it may be more usefull if the pithy stemmed
plants are only partly successful. Will they nest in bundles of dead pithy
stems?
Many thanks
Adam |
Depth of hole: I don't know what a minimum
depth would be, but mine are approx 15cm deep. As long as they are deep
enough for protection from the elements and producing nest cells then I
guess that may be enough. Someone else may have more info on this aspect.
Stem bundles: Bundles are more than fine for the bees as many of the
stem nesters are fairly social, particularly the megachilids. Dead plant
stems: Engineering the design so only being partly successful is one way of
having dead plant stems. The other of course is by using annuals
or species that have significant die back each year so there is a constant
supply of dead stems the following year that are either standing or
collapsed.
For green roofs, you should also consider bee box designs to go into brick
work. Old air bricks (which you don't see too often on modern houses) would
make ideal nesting boxes for bees. The can be installed in a similar fashion
as bat bricks in mitigation projects or on new-builds. Contract direct if
you want any more so we're not clogging up the group e-mail.Andy Jukes |
I have had homemade bee nests for three years
now - for the first two nothing happened, then I changed the nest sites
after reading advice and instantly at least three species moved in. They do
not like shade or overgrowing plants, or sites too near to the ground. So
south, SW or SE facing, in full sun, open, not overgrown are the best sites,
and they must be along a 'solid boundary' such as a wall or fence as bees
seem to move along these boundaries regularly. They have not inhabited a
nest bundle on a planted trellis for example. I find the best height is
between 30 and 60 inches from the ground.
I use bundles of hollow dead plant stems, roughly 17cm long, either tied
together with string/wire, or better still (but less attractive) stuffed
firmly into plastic tubes made of old juice bottles with cut off ends, which
i then tie firmly against the wall so they don't bounce in the wind. i leave
both ends open, but i have heard that the wind can fly through them too much
if the site is exposed - against the house wall they have worked very well,
the plastic keeping the rain off etc. i cut the stems slightly shorter than
the plastic tubes for the same reason, and the stems then don't rot as
quickly as they do if they are left open to the weather. I have just made
some wooden boxes to stuff stems in (as they look nicer - sad woman) but
will only know how effective they are later in the year.
The stems i use are hugely variable in size and species - so far the best
are sedum species, stipa gigantea flower stems, fennel, allium flower stems,
cow parsley and similar, old elder - almost anything that is hollow. i leave
most stems on plants overwinter for the seeds and only clear up in the
spring so i have lots of dead/dry stems by spring. I am not sure about the
green roof side of this - leaving stems in place on the plants might not
work so well - but you could try sedums as they would work well there and
would certainly suit other beasties. Why not add bundle nests close by for
the bees? With wood/post nest holes i think up to 17cm depth and various
sizes works best - the secret is definitely in the position, and wood should
obviously be untreated as bees are very sensitive.
hope this helps
Louise Hislop
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