The secrets of ivy

An important source of autumn nectar, as well as providing roosts for birds, rodents and bats, ivy is an unexpected champion of our waterways.

Words by Fergus Collins

Illustration by Alan Baker

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Take a walk on a sunny, late autumn day and you’ll enjoy the stirring sight of insect life buzzing in our hedgerows. Even as the days shorten and the nights generate the first frosts, a bit of afternoon watery warmth brings wasps, hoverflies, late butterflies and other flying critters out in their multitudes.

It’s odds-on that these late drinkers will be heading for the last-chance saloon – the nectar-rich flowers of ivy. One of our last native plants to flower, ivy offers abundant food in an otherwise lean period for insects, albeit delivered in yellowish-green dome-like clusters called umbels – a far cry from the soft, petalled stereotype of a ‘flower’. These buds mature into deep purple berries providing a reliable source of fat-rich food for birds throughout the winter and early spring, especially thrushes, woodpigeons and the first migrants such as blackcaps.

You would expect universal affection for such generosity but matters are never that simple. Ivy is a vine-like creeper and it survives by using other plants, especially trees, as a support as it climbs into the canopy to expose its glossy spear-head-shaped leaves to sunlight. It uses special stems with thick hairy roots, which are strong enough to penetrate mortar and brickwork on houses, to grip smooth surfaces. Many people believe that ivy strangles, starves or even poisons its host tree as it climbs, and call for the plant to be removed from woods and gardens wherever it is found.

“This is a myth,” says Canal & River Trust ecologist Laura Mullholland. “Ivy doesn’t steal or feed on its host – it gains its nutrients and water through its own roots. It doesn’t kill the tree it is climbing on.” Similarly, in its report on ivy, Arboriculture and Advisory Service (AAS) states: “There appears to be no scientific research or quantitative investigation of either the distribution of ivy or its effect on trees. As such there is considerable prejudice but no evidence.”

So where does the myth come from? “In old diseased or dying trees, ivy can begin to dominate the entire crown of the tree,” says Laura. “This can be a burden and, in the high gales of winter, the ivy’s evergreen foliage can act as a sail, catching the wind and toppling the tree. People think that the ivy has killed the tree when in fact it was already dying or dead.” A normal, healthy tree will be unaffected according to the AAS.

The myth becomes a problem when people, even well-meaning conservationists, take drastic action to remove ivy. “It’s heartbreaking when you see ivy removed on every tree in a protected woodland,” says Laura. The AAS also notes that when old, established ivy is removed from trees, the scars left behind can let in infections and diseases. The Canal & River Trust has a more sensitive approach and assesses each tree to see whether ivy is becoming a burden, especially on old trees. The wildlife value is so important: as well as its nectar-giving properties “the dense growth of ivy offers nesting and roosting sites for birds, rodents and bats. Wrens in particular love to skulk and forage in ivy,” Laura stresses.

Ivy has many cultural and mythological associations from being used to ward against evil in Celtic tradition (and hence finding its way into our Christmas decorations) to symbolising the Greek god Dionysus (the Roman god Bacchus), known for his drinking and often depicted with a crown of ivy. Perhaps this later association is due to the ivy’s vine-like leaves, climbing habit or grape-like berries… or maybe it’s because it offers the ultimate drinking hole for our autumn insects. And if the wildlife had its say, it would offer a very powerful defence of this generous plant.

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Posted on 08/11/2019