ivy - klimop - lierre
Love it or hate it? Ivy polarises opinion as few other plants - and has done so since antiquity. I love it - for the many good reasons that I set out here. Where will you stand when you’ve finished reading?
This post looks at:
1. What ivy is
2. Why ivy matters in ecosystems
3. The love-hate relationship with ivy since antiquity
4. Whether ivy really is destructive
5. Ivy in garden design
6. How to manage ivy in the garden
What is ivy?
Common or English ivy (Hedera helix) is an evergreen creeper/climber, native throughout the British Isles, Europe as far east as Ukraine, and into Asia Minor (northern Turkey, Iran). There are around 10 other species, a subspecies Hedera helix ssp. hibernica, and numerous cultivars of Hedera helix in all manner of variegation. This article is restricted to common ivy – klimop - lierre.
Ivy is common in woodlands, where it creeps until it encounters something to climb. It is common on heavier clay-rich soils and less abundant on poor and well-drained sandy soils [1], but nevertheless tolerates a wide range of conditions. Noted that it is more common in disturbed or secondary woodland, and struggles to establish in old, primary woods. Ivy climbs – up to 30m - in order to reach sufficient light to enable flowering, which usually happens once it reaches the top of whatever it is climbing. The flowering growth (or ‘arboreal growth’ is very different from the creeping/climbing growth. Shoots emerge horizontally from the stem, and are much more ‘woody’. Most noticeably the leaves have a very different shape, being light green and oval or heart-shaped rather than the familiar dark-green lobed leaves of lower growth. When cuttings are taken from this arboreal growth they will develop into small shrubs that no longer climb. These cuttings are frequently sold as Hedera helix ‘Arborescens’. So you can choose, in your garden, for a climber or a shrub form.
A glorious tangle of flowering and climbing/creeping growth
Ivy is the only Northern European plant from the Araliaceae family, a predominantly tropical family of plants. Other members include Fatsia (Japanese aralia), Schefflera (the umbrella tree, familiar as an indoor plant), and ginseng. It’s northern and eastern limits are at about -2°C winter average, although it withstands temperatures down to about -23C, while its southern limit appears to be defined by moisture availability.
Given its preference for warm and relatively humid it is no surprise that with increasing global temperatures, ivy is driving an increase in liana understorey in temperate forests [2]. It is not yet clear what the consequences of such systematic change may be, such as whether it may outcompete other species in the shrub and floor layers of woodlands.
Why ivy matters in ecosystems
Shelter
Ivy has a unique place in European flora, as the only large woody climber able to provide voluminous evergreen shelter for birds, bats and insects year-round. Our other lianas – clematis, bryony and honeysuckle – are also hugely valuable, of course, but are smaller and largely deciduous. They fill a different ecological niche.
In shrub form, ivy still provides evergreen shelter for insects and some birds year round.
Food
Over 100 insect species are associated with ivy as a food plant.
The flowers provide a critical source of autumn nectar and pollenfor late-flying insects before they go into hibernation. Some 70 insect visitors to ivy flowers have been recorded, including bees, wasps, hoverflies, micro- and macromoths, and butterflies such as red admiral and small tortoiseshell. The ivy bee (Colletes hederae) takes pollen only from ivy.
Male ivy bee Colletes hederae on ivy flowers
By Hectonichus - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14621494
The foliage is an important food plant for some butterfly and moth caterpillars such as holly blue, and the angle shades moth. Other insects, such as mites, scales, aphids, and whiteflies also feed on the foliage, and the tough ivy is unlikely to decline as a result. And yes, these insects - often classed as ‘pests’ for ‘eradication’ - are of enormous ecological importance to the longer food chain, attracting species such as ladybirds, lacewings, spiders and small birds.
Sixteen bird species have been recorded eating ivy berries, including robins, blackbirds, thrushes and blackcaps.
Some 50 fungi species are associated with ivy.
To put these numbers in perspective, other self-clinging climbers such as Boston ivy (Partenocissus) and climbing Hydrangea (H. anomala var. petiolaris) are associated with a few insects, and provide some degree of deciduous shelter. Similarly, other evergreen shrubs such as Viburnum or Mahonia provide some limited food potential. But as non-natives, the number of associations is a fraction of those that have, logically, developed through co-evolution since the end of the last glacial maximum (some 14,000 years ago). This is a subject for a whole other blog, and I will return to it.
Love-hate relationship with ivy since antiquity
Early reference to ivy appears in the Iliad, [3] when Homer describes the staves or fennel-stem sceptres (thyrsi) of the devotees of Dionysus adorned with ivy and vines [4]. The association of Dionysus with ivy goes further back, to his mythical triumphant return from a military campaign in India wearing a wreath of ivy. The theme recurs in Greco-Roman art.
Ancient Roman relief in the Museo Archeologico (Naples), depicting Dionysus holding a thyrsus and receiving a libation, wearing an ivy wreath, and attended by a panther
Author: Sailko. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
The Greek philosopher Theophrastus (c. 371 – c. 287 BC), so-called father of botany, left us two astonishing botanical treatises: Enquiry into Plants(Historia Plantanum) and On the Causes of Plants, the first known scientific description of the botanical world [5]. It's fair to say Theophrastus was not a fan of ivy:
“All ivies have numerous close roots, which are tangled together woody and stout, and do not run very deep; but this is specially true of the black kind and of the roughest and wildest forms of the white. Wherefore it is mischievous to plant this against any tree; for it destroys and stanes any tree by withdrawing the moisture. This form also more than the others grows stout and becomes treelike, and in fact becomes itself an independent ivy tree, though in general it likes and seeks to be against another tree, and is, as it were, parasitic. Moreover from the first it has also this natural characteristic, that it regularly puts forth roots from the shoots between the leaves, by means of which it gets a hold of trees and walls, as if these roots were made by nature on purpose. Wherefore also by withdrawing and drinking up the moisture it starves its host, while, if it is cut off below, it is able to survive and live…... Such are the facts about ivy.” (Chapter 3.18.8)
Pliny the Elder (Gaius Plinius Secundus AD 23/24 – 79) 350 years later took a similar view.[6]
“It is said that the ivy now grows in Asia … and that Alexander, in consequence of the rarity of this plant, had himself crowned with it, after the example of Father Liber (Roman name for Dionysus or Bacchus), when returning victorious with his army from India: and at the present day even, it is used to decorate the thyrsus of that god, and the casques and bucklers employed by the nations of Thrace in their sacred ceremonials. The ivy is injurious to all trees and plants, and makes its way through tombs and walls; it forms a haunt much frequented by serpents, for its refreshing coolness; so that it is a matter for astonishment that there should have been such remarkable veneration for this plant.”
So, is ivy really destructive?
With all due respect to Theophrastus and Pliny ….. ivy really does not actually ‘strangle’ trees. Ivy has a separate root system in the soil through which it absorbs the nutrients and water it needs, and is not able to parasitize a host tree. The aerial ‘rootlets’ are simply for clinging on, and the only danger ivy poses to trees is where it becomes so dense as to form a kind of ‘sail’ within the canopy. Within woodlands this is rarely problematic, as the canopy prevents such dense growth.
As for walls, a 2010 project for English Heritage [7] aimed to investigate the effects of Hedera helix canopies on walls in England in order to test whether ivy serves as a beneficial (bioprotective) or detrimental (biodestructive) agent on historical walls and buildings for conservation purposes.
In essence this report found that where walls are solid in structure, with sound brickwork and no problems with rising damp, ivy had essentially positive effects as a wall covering. It acted as an effective insulator on all sites tested, by lowering the maximum daily temperature of the wall, raising the minimum daily temperature, and, on average leading to a 3.5 x lower daily range of temperatures across all sites. The precise degree of mitigation depended on factors such as the density of the ivy and orientation of the wall.
Apart from its benefits as an insulator, the ivy also mitigated damage caused by cycles of high and low temperature and wetness/dryness, and by preventing rainwater, pollutants and other particulates from reaching walls. In sound stone walls, even the aerial rootlets were found not to cause any damage [8]. As for rooting, it was noted that “ivy only roots into the wall when there are holes in the wall, and that rooting into the wall is especially encouraged when the ivy is cut off at the base of the stems in an often misguided attempt to kill it off.”
The report notes, on the other hand, that ivy – and indeed any other climber on a wall - might also keep walls affected by rising damp etc. wet by reducing evaporation from the surface. Where walls are vulnerable, roots may indeed be put down in the wall and cause physical breakdown. And aerial rootlets may chemically deteriorate vulnerable minerals.
The crucial issue is the initial soundness of the construction, not the presence or otherwise of ivy. If you have a solid wall, then ivy not only provides a marvellous habitat for wildlife, but can also act as an important thermal insulator, and actually protect the wall from deterioration.
Ivy in garden design
Picturesque movement
Ivy very much had its heyday in the Picturesque period of garden design, a movement that emerged in the second half of the 18th century in England.
The first to use this term was one William Gilpin [9] in his Essay on Prints, where he defined the picturesque as "that peculiar kind of beauty which is agreeable in a picture" [10].
Uvedale Price, among others, developed the theory, publishing in 1794 An Essay on the Picturesque as Compared with the Sublime and Beautiful. The ‘picturesque’ fell somewhere between Edmund Burke’s ‘beautiful’ (that which is well-formed and aesthetically pleasing – pretty sights, if you will) and ‘sublime’ (that which has the power to compel and destroy us – mountains for example). On his own estate in the Wye Valley he nurtured the essential ‘natural’ qualities of the picturesque such as wildness, irregularity and sudden variation.
Gilpin, Price and others were working in an age when, in England at least, an earlier appreciation for landscapes as fertile places for production or for formal gardens of highly geometric design in which nature was firmly under the control of the human hand, had very much given way to a broader appreciation of rugged and wild nature. This fascination with ‘picturesque’ scenery and ‘prospect’ views is reflected in aesthetic tastes, with landscape painting enduring in popularity into the late 19thcentury. In garden design, Humphrey Repton became the most well-known proponent of the picturesque movement. He prepared some 400 designs around England, including Tatton Park, Bayham Abbey on the Kent-Sussex border, and the themed gardens at Woburn Abbey.
This 1809 sketch shows a typically ruined, overgrown arch at Bayham Abbey, shortly after improving works by Repton.
The aesthetic ideal was found at Tintern Abbey in the Wye Valley, a favoured destination of tourists in search of the picturesque. Writing in 1836 Thomas Roscoe praised:
‘the rich heavy folds of Nature’s most graceful drapery, luxuriant ivy, which adorns the lofty aisles and transepts of this majestic edifice, and scarcely suffers us to regret that it is a ruin ….’
Ivy in modern garden design
Most of us do not have estates, or romantic ruins of abbeys to adorn with wild and exuberant ivy these days of course. But it is fair to say that ivy – and other elements of ‘natural’ vegetation - are increasingly appreciated for their wider ‘ecosystem services.’ The English Heritage inquiry illustrates this nicely. In forestry management aswell, ivy is no longer seen as a destructive element and it is not removed.
In private gardens, homeowners are also increasingly aware of the benefits of ‘climate robust’ planting, that will weather the challenges of climate change. Not wither. Ivy has additional benefits, of course, as it also serves to support our alarmingly declining population of insect life, and by turn fauna higher up the food chain.
It can be used in many ways. One particularly striking effect is created by deploying ivy as an ecologically interesting ground cover. It grows faster and is much more wildlife-friendly than the ubiquitous Cotoneaster – which although the berries are interesting for blackbirds risks becoming invasive (as those very same birds spread the seeds of course).
Garden at the entrance to Gaasbeek Museumtuin with serpentine streams of ivy
And an increasingly popular, and increasingly available, form of ivy in the smaller garden is shrub ivy (struikklimop). It grows as a dense, rounded shrub, to around 1m tall, producing both flowers and berries. It can be used in so many ways.
It can be clipped to form a small hedge, as a disease-free alternative to Box. You can see some beautiful examples here:
http://www.egelantier.be/index.php?Egltl=33&EGltML=6
Or you could use ivy as a stand-alone evergreen accent shrub, clipped to replace expensive yew and Osmanthus mounds.
Or leave it to grow out as a taller shrub behind the border.
It is a wonderful, versatile shrub for you wildlife-friendly garden!
Managing ivy in the garden
Ivy on walls
My best advice is: feel confident in using ivy if you are looking for a vigorous climber to cover solid walls. It will bring far more benefits than damage, and is far cheaper than some expensive system of cables for non self-clinging climbers.
Be prepared for annual pruning. Generally the right time to do this will be in late winter, after the worst of the cold weather. This will leave the berries for birds as long as possible, as well as leaving the habitat intact for overwintering insects. But you need to prune before birds are likely to start making nests in it, and to allow a long enough growing season for next year’s flowers and berries. In any case, check for signs of nesting before you prune! It’s not a bad idea, either, to rotate the pruning of different sections over different years, to leave some habitat intact.
Ivy as ground cover
Use it liberally to create ecologically sound ground cover in spaces where you can trim the edges to keep it in shape, including on slopes.
Ivy as a shrub
Trim it to shape, and it will reward you with either a beautiful hedge or stunning accent points in your garden, with the same pruning guidelines as for climbing ivy above.
Conclusion
I hope you found this post interesting and useful, and that it will inspire you to treat yourself to the many natural wonders that ivy can bring to your garden. I will leave you with a view of one of my favourite examples of the modern use of ivy in garden design. This from the silver garden in the marvellous Parc André Citroën, Paris, designed by Gilles Clément and Alain Provost.
The silver garden, Parc André Citroën. The glossy leaves of ground covering ivy on the side banks are the perfect foil for silvery, glaucous foliage in the centre.
[1] https://besjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2005.01021.x
[2] growing by an average 14% coverage between 1933 and 2015
https://pureportal.inbo.be/en/publications/increasing-liana-frequency-in-temperate-european-forest-understor
[3] conventionally dated to the late 8th or early 7th century BC
[4] From Iliad Book 6
“Not long Lycurgus view'd the golden light,
That daring man who mix'd with gods in fight.
Bacchus, and Bacchus' votaries, he drove,
With brandish'd steel, from Nyssa's sacred grove:
Their consecrated spears lay scatter'd round,
With curling vines and twisted ivy bound;”
Incidentally, having taken on Dionysus, Lycurgus finished up blinded and mad
[5] He examined the anatomy of plants and propagation (he identified seed germination), properties and uses of different types of wood, systematised plants into categories (wild trees, under shrubs, pot herbs, cereals and legumes), recognised links between climate, soil and vegetation, and wrote extensively on the medicinal uses of plants. Remarkably he described trees and shrubs ‘from abroad’ – Egypt, Libya, Asia, northern regions, aquatic plants from the Mediterranean, wetlands, reeds and rushes.
[6] Chapter 62, see:
http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D16%3Achapter%3D62#note8
[7] https://historicengland.org.uk/research/results/reports/7260/IvyonWalls
[8] Porous bricks and mortar were not investigated.
[9] a cleric, headmaster, travel writer and amateur artist
[10] He further developed his principles of picturesque beauty over the course of the following decades (essentially a set of rules for depicting nature), through his knowledge of landscape painting and his travels around, and observations of, landscapes in England such as the Wye Valley and the Lake District.