Val Bourne: here’s a tiny black bee that relies on bellflowers
Val looks at a tiny black bee that relies on bellflowers
ILOVE bellflowers and I really enjoy growing Campanula lactiflora ‘Prichard’s Variety’ for its rich-blue flowers. It begins to flower just after the roses and, if you cut the old flowers off, it produces another lot. It can give six weeks of flower, if deadheaded regularly, and fills the gap between the first flush of roses and the second.
‘Prichard’s Variety’ was raised by Maurice Prichard of Riverslea Nursery, which used to be in Christchurch, Hampshire. I’ve grown this plant for 50 years in various gardens, but it’s been around for longer. It has a mop of richblue flowers on a 3ft (1m)-high plant, and it’s something I wouldn’t be without.
We also grow a tall biennial called
C. trachelium in the garden. Commonly known as the nettle-leaved bellflower, this bears largish bells on one stem in various shades of blue. Our third is the delicate harebell, C. rotundifolia, with its 1ft (30cm)-high trembling stems of tiny grey-blue bells. This lover of warmth and sandy soil grows in our stone paving and on nearby limestone slopes.
The bellflowers I’ve mentioned are all British natives. There are five native species of campanula in Britain and four of them are garden-worthy plants.
Campanula lactiflora, known as the milky bellflower, is a plant of damp places scattered through Britain. The nettle-leaved bellflower, C. trachelium, is frequently found along hedge banks and on woodland edges. The harebell, named C. rotundifolia because the first pair of leaves is round, inhabits sandy light soils. C. glomerata, the clustered bellflower, is also found in the wild. On the Lizard Peninsula in Cornwall it barely reaches 4in (10cm) in height. However, in richer garden soil it’s about 1ft (30cm) high and prone to spreading.
The fifth native species, the spreading bellflower (C. patula), occurs mainly on the Welsh borders and in the West Midlands. It’s endangered, so it’s a priority species under the UK Biodiversity Action Plan, according to the charity Plantlife
(8 plantlife.org.uk). Reasons given for its demise are changes in woodland management, meaning less coppicing, and overuse of pesticides.
Native plants develop a special relationship with our insect life, because they’ve evolved side by side for millennia, so it’s no surprise that there is a specialised tiny black bee that visits harebells and other campanulas.
Chelostoma campanularum seems to have two names – the small scissor bee and the harebell carpenter bee. It flies between June and August, and it’s common in much of England, particularly the southern half, although it’s absent from Wales, Scotland and Ireland.
Although this bee is tiny, it’s easily spotted because the males roost inside the flowers in cool conditions. The males have two pegs on their lower abdomens to help them grip onto the flower. If you look into a campanula flower you may well see this tiny black bee at rest. You may even see a cluster on one flower.
The Bees, Wasps and Ants Recording Society website (8 bwars.com) has a fact sheet that explains that the harebell carpenter bee specialises on harebell, nettle-leaved and clustered bellflowers. These bees have also been recorded in gardens collecting pollen from geranium cultivars. The fact sheet states: ‘In order to collect the pollen, the female [harebell carpenter bee] lands on the anthers of the flower, holding them by gripping with her mandibles and front legs, while using her back legs to push the pollen backwards on to the hairs on the underside of the abdomen.’ The female has more hairs on her underside than the males do.
The harebell carpenter bee nests in existing holes in dead wood, small nail holes, old building timbers and fence posts. Often the holes have been made by small-bore beetles. The nest partitions are made of mud and the cells are arranged in lines.
My organic garden teems with life on every level, and the lack of pesticides brings its own rich rewards once again!
“This specialised tiny black bee visits harebells”