Another reason not to poison ivy

Saving the bees is a popular cause, and with good reason. They’re essential for pollinating many important crops. However, we don’t always coördinate our aims and our actions. There are concerns that various chemical treatments, either neonicotinoid pesticides or fungicides could be responsible for the reducing the bee population in the UK. There’s probably many other reasons. 97% of lowland meadow in the UK has been lost, a scale of destruction that makes the loggers in the Amazon look amazingly unambitious. But there’s all sorts of little actions that make it worse.

Ivy is currently a villain. It climbs up walls and around trees. It doesn’t actually kill trees, but that gets overlooked. It can make damage on walls worse if the wall is already in a bad state. It can also insulate walls, so properly managed it will save you money. Recent research also shows that it undervalued in supporting bees. The title of a recent paper spells it out very clearly: Ivy: an underappreciated key resource to flower-visiting insects in autumn by Mihail Garbuzov and Francis Ratnieks at the University of Sussex.

When I think of ivy I picture the lush green leaves, but it’s the small white flowers that are important. They appear in the autumn at a time when there are few other flowers. Garbuzov and Ratnieks examined hives around Brighton to find out what the bees were foraging for. The results surprised me. Honey bees need ivy, a LOT. During September and October Garbuzov and Ratnieks found that 89% of the pollen pellets the honey bees brought back were from ivy. They also found that the majority of honey bees and bumble bees were bringing back ivy nectar to build the winter honey stores. Ivy nectar is unusually high in sugars.

The key factor in ivy’s importance is timing. Spring brings out the blooms and it’s a feast for insects that are bringing up the next generations over the summer. Winter in contrast is a famine and hives need stocks and supplies. The late flowering of ivy provides a boost to bee hives to put them in a better position for surviving overwintering.

Garbuzov and Ratnieks go so far as to say that ivy may be a keystone species, a species that has a disproportionate effect on the local environment. Ivy’s ability to feed bees, wasps and flies in the autumn provides a better chance of survival and so more insects to reproduce in the spring, not simply to pollinate other flowers, but also to provide food for predator species.

There is no obvious connection between ivy and many other crops species, but it looks like Garbuzov and Ratnieks have shown that what looks like a very localised problem What do I do with my ivy? has consequences much further afield.

The Laboratory of Apiculture and Social Insects has produced this video on how to identify insects on ivy. The university has also blogged the paper with some nice photos.

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Insects on ivy flowers. Photo tomylees/Flickr. [cc]by-nc-sa[/cc]