Lime species are excellent forage for bees, especially honeybees and short-tongued bumblebees such as Bombus terrestris. There are 30 odd species of Lime, all native to temperate regions, and 3 are prevalent in the UK: common
lime (Tilia x europaea), small-leaved lime (Tilia cordata), and large-leaved lime (Tilia platyphyllos). The common lime is a hybrid of the other two and is the lime you often see in towns and cities, on streets and avenues. They can be very old and grow up to 40m or so. Both large-leaved lime and common lime are particularly good for bees as their flowers are pendant (they hang down) meaning nectar is not easily washed away by adverse weather such as rain.
Nectar (the sweet sugary substance secreted by flowers to attract bees and provide them with energy) is produced copiously on the inner side of the sepals of the lime flower. Nectar production in limes is acute in mornings with the optimum temperature being around 20 degrees celsius. It seems that in recent years beekeepers have reported poorer provision of lime nectar, perhaps due to adverse/wetter weather. Trees of the same species may differ in the time of their flowering, even in the same area, which is good for bees as it can provide a longer time period for them to be able to forage on the nectar.
Lime (especially the common lime) is a major producer of honeydew, a sticky, sugary liquid produced by aphids that live on the trees. Because of this it has been planted less and less in recent years and lime trees are reducing in numbers. People find the honeydew problematic as it comes off the trees and has caused pavements to be slippery, as well as making a mess on cars and public seats. Limes are also seen as too large for many streets now, they often drop their leaves early, ruining the feel of late summer, and they have a soft bark susceptible to injury.
Perhaps we need to redress this quiet lack of favour for the lime as it is a hugely valuable tree to many bees. It is only really the common lime that is such a perpatrator of the honeydew issue. Other limes that could take its place include Caucasian lime (Tilia x euchlora), Mongolian lime (Tilia mongolica), and Japanese lime (Tilia maximowicziana) to name but 3.
Planting young lime trees for the future is undoubtedly a positive thing to do, if you aren’t so concerned about your car’s squeaky clean look that is.
Kirk, W. and Howes, F. (2012) Plants for Bees, International Bee Research Association, Cardiff.