Tree of the month: Ivy

The moon was new yesterday so we’re now in the Month of the Ivy. The popular version of Ogham tree months is based on a 19th century invention starting at a time of year barely of interest to ancient Celts. But I’m following the cycle of 13 lunar months for appreciating 13 tree species. I started the cycle two months ago because that fits our seasons here in Britain.

After Hazel and Bramble, in this cycle comes Ivy. Like several of the other ‘Ogham trees’ the common ivy (Hedera helix) isn’t an actual tree but it’s a woody perennial. It’s a climbing plant, widespread and common in Britain, growing on trees and walls or sprawling across ground.

Many places in Britain and in other places where H. helix is native or naturalised would look naked without the familiar ivy. It’s evergreen so ivy stands out at this time of year. Unlike many of the woody perennials and many of the grasses and herbs, it’s not turning colour and it’s not dropping its leaves.

Many people believe that ivy damages trees by strangling them and damages walls by growing roots into them. This may not be true. Andrew Cowan at ArborEcology says that on trees, ivy can be more a sign of stress than a cause of stress. The Woodland Trust (WT) values ivy and conserves it on trees. The WT removes ivy when it weighs trees down or when it impedes access for humans, but otherwise retains it for birds and insects.

Still, the Royal Horticultural Society (RHS) classes ivy as a weed. The RHS says that there ‘may be times when its control is advisable’ and suggests methods for ivy control.

When ivy grows on modern and ancient walls and on gravestones, opinion can be strong. Heather Viles at Oxford University, with English Heritage (EH), considered how ivy on walls should be managed. From that research Alan Cathersides of EH concluded, ‘Ivy is a noble and agreeable plant.’

Val Osbourne of the Royal Society for the Protection of Birds (RSPB) says that gardeners should grow ivy as food for hungry birds. In fact, this plant benefits insects as well as birds. The RSPB’s guide to wildlife gardening recommends ivy because this plant provides food for several kinds of birds and insects. It’s particularly important for caterpillars of the holly blue (Celastrina argiolus).

If you see wasps on ivy, you don’t have to assume that’s bad. Even the common wasp (Vespula vulgaris) may be doing something useful. Vespula spp. are important pollinators for ivy. So avoid the wasp because it might sting you, but don’t rush to kill it. Thanks to the wasp, there’ll be ivy berries for birds to eat when autumn turns to winter.

[Edit] My fellow blogger Spencer Woodard at Anthropogen tells us about the beauty and medicinal value of H. helix.

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About argylesock

I wrote a PhD about veterinary parasitology so that's the starting point for this blog. But I'm now branching out into other areas of biology and into popular science writing. I'll write here about science that happens in landscapes, particularly farmland, and about science involving interspecific interactions. Datasets and statistics get my attention. Exactly where this blog will lead? That's a journey that I'm on and I hope you'll come with me.
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6 Responses to Tree of the month: Ivy

  1. I love ivy, but it would completely take over our garden!

    • argylesock says:

      Yes I’ve hacked it back when it’s grown where it’s unwelcome! The old definition of a weed: a plant in the wrong place.

      • Exactly! I’m constantly having to remind people that it’s only a weed if you don’t want it! I love ivy and I love passion flowers, but sadly I know that these would be detrimental to both our garden and the foundations of our house.

  2. Carol Hague says:

    We have ivy growing from the far side of the back wall of our garden. We cut it back to keep it under control, but otherwise leave it alone, for the reasons you cite – the blue tits seem to enjoy foraging in it for creepy-crawlies for a start 🙂

  3. narf77 says:

    I thought that ivy was poisonous but Steve made an ivy peace sign for a horticultural unit where we had to produce some sort of topiary (I used a prostrate cotoneaster) and “something” keeps it very VERY neatly clipped on a regular basis 😉

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