White Dead-nettle: A Feast for Bumblebees in Early Spring
White Dead-nettle is a perennial plant of the Mint Family that grows well on the sunlit edges of paths, in or close to woodland. It is not found in all woodlands, but we are lucky to have it abundant in some of those in Dalgety Bay.
Having a preference for growing along path edges does however make it quite vulnerable to path-edge tidying, especially as its leaves closely resembles those of the unrelated Stinging Nettle (White Dead-nettle does not sting).
This year it has particularly benefited from the heavy rains in February and then just enough rain to keep it going in March and early April so it is particularly plentiful. Being one of the few flowers available in early spring it is particularly important for most of the bumblebees in our area, providing food for the queens as they emerge from their winter hibernation, establish a nest, and start to feed their first broods of workers.
What the Survey Data shows
To see just how important it is, is demonstrated in the data from the bumblebee/flower surveys. The survey in 2021 was a repeat of the one I did along the same route in 2015. The results of both surveys show that in the 6 or 7 weeks from early to mid-April when the counts started through to the end of May, it was a constant feature of counts of bumblebees visiting flowers. The other two main species being used at that time were Gorse, in the area between the gun emplacements and steps, and Yellow Archangel in Bathing House Wood.
Looking just at the total counts of all bumblebee species over the first 6 or 7 weeks of the surveys in 2015 and 2021, between 80% and 75% of the 192 and 190 bumblebees counted in these early weeks were feeding on White Dead-nettle in 2015 and 2021 respectively. Gorse accounted for 4% and 12% in the two years and Yellow Archangel 9% and 3%. Seeing how abundant Gorse was on the survey route it may be surprising that it was not more visited for pollen and/or nectar, so the rewards available from White Dead-nettle appear to be greater than those from Gorse. Evidence for this may be seen from the short time bumblebees spent on each individual Gorse flower compared to the long time they spent immersed in a White Dead-nettle flower. More energy would need to be expended flying from flower to flower on Gorse rather than being able to spend a longer time on each White Dead-nettle flower.
The importance of White Dead-nettle is even greater for one species, Garden Bumblebee, with 93% of visits to this flower out of 61 recorded on all flowers in these weeks in 2015 and 100% out of 33 in 2021.
As analysis of the survey data continues, future postings will provide more information on flower choices by the different species of bumblebee that can be seen here. The findings so far confirm that this one species, White Dead-nettle, plays a vital part in maintaining and enhancing the biodiversity that has been part of the work of DBCWG from its start in 2014.