Happy New Year! Since we have a few days to go until Twelfth Night, there is time to shoehorn in a festive reference:
“The holly and the ivy,
When they are both full grown,
Of all the trees that are in the wood,
The holly bears the crown.”
I do like Holly, Ilex aquifoilum, but I prefer Ivy, Hedera helix. And Ivy isn’t just for Christmas – it provides a year-round habitat and food source for wildlife.
Ivy is an evergreen climber and is native to western, central and southern Europe but it has been introduced into Australia, New Zealand and the western United States. It is Britain’s only evergreen liana. It belongs to the family Araliaceae, a family of around 250 species found in the Americas, Eurasia, Africa, Australia, New Zealand, New Caledonia and Pacific islands. Other well-known members of the family include Ginseng, Panax quinquefolius, whose roots are used in herbal medicine, the British wild flower Marsh Pennywort, Hydrocotyle vulgaris (which was considered to be a member of the Umbelliferae when I did Botany), the widely grown ornamental shrub Fatsia japonica and the Rice-paper Plant, Tetrapanax papyrifer, which I wrote about in October 2013.
Six pages of Richard Mabey’s ‘Flora Britannica’ are devoted to Ivy. It has a rich folklore, some of which is documented by the Owlcation website. I like Ivy’s association with the sale of alcohol – in medieval times ivy-covered poles were used to advertise taverns. (This led to the expression “Good wine needs no bush“.) Goblets were sometimes made out of Ivy wood and Ivy berries were supposed to overcome the bad effects of alcohol, although trying this is not a good idea because the plant is mildly poisonous. The Plants For A Future website describes Ivy as a bitter aromatic herb with a nauseating taste, so possibly it is better to stick with that hangover.
Various other uses for Ivy include making a brown dye from the twigs, using the leaves to wash clothes or restore black fabrics and, under the supervision of a qualified practitioner, as a folk medicine. The last point is important, as Ivy leaves and berries contain a saponin known as hederagenin, which can cause breathing difficulties and coma if ingested in sufficient quantities. Ivy sap can also cause dermatitis with blistering and inflammation, possibly due to the presence of polyacetylene compounds.
Other English names for Ivy include Cat’s foot, Me Hoofe, Robin-run-in-the-edge, True Ivy and Tun-hoof. Our Ivy, Hedera helix, is not related to the American species known as Poison Ivy, Toxicodendron radicans (Eastern Poison Ivy) and the related Toxicodendron rydbergii (Western Poison Ivy).
As the tough stems of Ivy creep along the ground, they root into the soil at intervals and produce lovely deep green leaves with three to five lobes and contrasting pale veins. These are known as shade leaves and the plant produces them as it grows over the ground and then first starts to climb up trees or walls. This growth can be very dense and will smother out other plants which is why it is often planted in gardens as a groundcover plant and especially as it happily grows in dense shade and dry conditions on poor soils. There are many garden cultivars, with different leaf shapes and colours.
Once the Ivy has scrambled its way up a tree or building and is growing in full bright sunlight it will it produce what are known as sun leaves. These are a lighter shade of green with less prominent veins and are a pointed oval in shape. It is only when the plant has put on a good growth of these leaves that it will then produce its lovely delicate flowers. An interesting fact about Ivy is that if you cut a stem of sun leaves and root it, it will grow into a self supporting free standing Ivy Bush.
Ivy is a very divisive plant, loved by some but loathed by many – including some foresters and custodians of ruinous buildings. It has a reputation for strangling or smothering trees and is sometimes assumed to be parasitic, sucking the life out of its host tree. But this is untrue – Ivy makes all its own food through photosynthesis and has its own root system for drawing up water and nutrients from the soil.
Ivy uses trees and walls as a support to scramble up and it can eventually clothe an entire tree in an evergreen mantle. This can deprive the tree’s leaves of light and, on dry soils, Ivy’s roots will compete with the tree for available water. Eventually the lush growth of Ivy at the top of the tree can make it top-heavy and vulnerable in strong winds or heavy snow fall, when the extra weight can bring branches down or even topple the tree. Because of this, foresters will regularly hack through the thick stems of Ivy enveloping trees near their base, cutting out a foot or so and then leaving the whole lot on the tree to wither and die, leaving an unsightly mess.
Ivy on walls and buildings can sometimes do damage too, but it can also protect walls. As the Ivy scrambles up any structure, it clings to it with little rootlets coming off the main stems. When the rootlets find crevices in walls, the plant will then send out proper roots into the structure and as these grow they can split any cracks further open. Often the main problem with ivy on old walls is when you try and pull it off – it clings so tenaciously that you can end up pulling off bits of wall with it. Because of this, on many old ruins it is now left in place, indeed sometimes it is the Ivy that is actually holding the structure together and keeping it upright. In cemeteries Ivy will cover gravestones, making them unreadable and potentially damaging some memorials, so it is often removed before it puts on too much growth.
However, if Ivy is allowed to climb up a dead or moribund tree, it can extend its wildlife habitat value beyond the life of the tree. Dead and decaying trees are of supreme wildlife importance to a variety of rare and vulnerable creatures, from beetle and moth larvae to roosting bats and nesting birds. Unfortunately such trees often end up being felled as they can pose a threat to people and property when they eventually come down. There is also a tendency amongst some to constantly ‘tidy-up’ the countryside by removing ‘dangerous’ trees even in the middle of woods.
Provided Ivy is given the occasional trim, it is a very beneficial plant, as it forms a kind of high-rise hotel for wildlife. Being evergreen, it provides shelter for invertebrates all year round, nesting sites for birds in the spring and summer and food for much of the year.
On woodland floors and hedge banks, a thick covering of Ivy leaves will conceal the entrances to mice and vole holes as well as bumblebee nests. Higher up, on old walls, Wrens, Blackbirds, Robins, Thrushes and other birds will nest in its dense cover. Ivy’s dense evergreen foliage provides ideal places for hibernating insects to securely sit out the winter, including butterflies like the Small Tortoiseshell (pictured above), Brimstone and Comma, as well as hoverflies and ladybirds. In spring a big clump of Ivy in a sunny position is a good spot to to look for emerging hoverflies and ladybirds as they crawl out of the dense cover to warm themselves before flying off to forage.
Ivy flowers in autumn are perhaps its greatest gift to wildlife. Ivy flowers are produced in small, dense umbels and are pale yellow-green in colour. They are produced in September and will carry on flowering through October and well into November. Ivy is one of our latest flowering native plants and is an extremely important source of nectar for honeybees, wasps, hoverflies and butterflies. The flowers have a distinctive scent – a heady smell of honey – and some beekeepers harvest Ivy flower honey from their hives. It has a very distinctive taste, which I personally find a bit too overpowering.
On a sunny autumn day Ivy flowers will be covered in honeybees, so much so that you can actually hear the hum of their wings. If you search amongst the honeybees you will hopefully find some hoverflies, usually Eristalis species (Drone Flies) which mimic the honeybee in coloration but also sometimes something a bit more exotic like Volucella zonaria, a very large migrant hoverfly that is a perfect hornet mimic.
Ivy flowers are also a magnet for wasps, including the males, with their long antennae. There were good numbers of wasps on Ivy flowers this autumn, but numbers have plummeted in the last few years. Although they can be a nuisance at picnics, wasps form a vital part of the web of life. They are important pollinators and pest controllers, collecting and killing numerous caterpillars, whitefly and other nuisances to the kitchen gardener.
Another beneficiary of Ivy’s rich nectar is the Red Admiral butterfly which can often be found feasting on the flowers. In milder winters the butterfly may well hibernate in the dense leaves but they can be killed off by heavy frosts and long cold spells.
Holly Blue butterflies lay their eggs on the infant buds of the Ivy, their caterpillars feeding on them as they develop. Once the flowers are pollinated, the small green berries start to swell, turning brown and then ripening a lovely deep blue-black. These will persist right through the winter, surviving frosts and snow. They are beloved of Wood Pigeons and are a saviour to Blackbirds and Thrushes as well as overwintering Blackcaps.
When I wrote about Sea Aster last month, I mentioned the Sea Aster Bee, Colletes halophilus. Since 2001 the related Ivy Bee, Colletes hederae, has been spreading northwards in the British Isles. It reached Norfolk in 2014 and by the end of last year it had reached North Yorkshire and Lancashire. It is a very distinctive species, emerging late in the summer ready to feed on Ivy flowers. We found it in several parts of North Norfolk in our week staying at Wells-next-the-Sea, and there is a large colony on the outskirts of Costessey, only a few miles away from home. It is likely to continue its spread in 2017, so keep a look out on Ivy flowers this autumn.
Some plants benefit directly from Ivy too. Ivy Broomrape, which I wrote about in June 2016, is a parasite that grows on Ivy.