Transatlantic seeds revisited
Another nameless plant

Ivy is not always a menace

News arrives of an American insurance company getting their knickers in a twist (as we say in England) about ivy growing up the walls of a brick-built house. The broker passes on the message from the insurance company: “If you can't take the ivy down they may chose to not renew your policy.”

So – are they mad, or are they wise and prudent?

In its native habitat ivy, Hedera helix, clings to tree trunks using aerial roots which are produced from stems as they come into contact with almost anything: bark, bricks, glass even. The function of these very short roots is mainly support, although they do absorb some moisture too.

Ivyonhouse On a relatively new brick-built house, the bricks and mortar are so hard that the ivy roots cling without causing any problems. In fact the presence of ivy can be advantageous: it provides extra winter insulation, it certainly sheds water from the wall and keeps it dry. It also provides a valuable nesting and roosting site for songbirds and food for butterflies and birds. And I’ve seen ivy that covered a relatively modern brick wall from top to bottom fall off completely without revealing any damage at all. In that case it couldn’t grip sufficiently well to support itself.

On older houses - and in Britain that usually means houses built before about the 1930s - any problem usually arises because the mortar used between the bricks is softer and as those aerial roots grip then fragments are loosened. You can see from these pictures of ivy growing on a brick house built in the 1800s how it can get out of hand. But here the value of the ivy in keeping the wall dry is also important. More of a problem is the ivy getting under and loosening the roof slates – but with relatively few American houses built of brick or roofed in slate this is less of an issue in the US. Yet in the US ivy is regarded as more of a villain than it is in Britain.

A huge range of problems is attributed to it from the quite reasonable fear of damage to certain types of building to harboring both rats and bacterial leaf scorch (a significant disease of trees). What was interesting is in that in a recent exchange the prevailing opinion was “every little bit of damage we can do to ivy's reputation is a good thing” and “I have to give (the insurance company) kudos for showing leadership in this area”.

No one asked: is the insurance company’s attitude reasonable? And then you see comments like “English ivy is a menace everywhere” - when in almost twenty states it doesn’t grow at all and is only cited as noxious in two – and “ivy strangles native trees” when it doesn’t strangle trees at all, is most vigorous in trees whose canopy is already thinned by disease or other causes and whatever it does is not restricted to natives.

HederaRippleJytte600 Now don’t get me wrong: I’m not saying that English ivy is a saintly plant with no faults. It is indeed a menace in some areas, and the insurance company, in this particular case, may be taking a prudent approach. But in other areas it’s a valuable ornamental climber, an attractive ground cover, useful in hanging baskets in areas not cold enough to kill it and a pretty and tolerant house plant.

But it’s not invasive in states where it doesn’t grow. And is ivy’s value as shelter and food for wildlife, which is much appreciated in its native Britain, utterly redundant elsewhere?

Can we please have less hysteria and panic and more reality and reason?

Comments

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eliz

I love the look of ivy but it is both rampant in the garden and does need to be pulled away from my 1870 brick house. I still love it though and if I can then everyone else can put up with it too!

VP

I'm in a real quandary about ivy. I value it for the wildlife it nourishes and at first I welcomed it across the fence into my UK garden from the public land next door.

But now I find it everywhere in the garden and it's out competing the other groundcover plants - also chosen for their wildlife nourishing qualities...

Graham Rice

That's exactly right: being conflicted about ivy is perfectly reasonable and logical. Condemning it utterly and universally is not.

luise h.

I have Ivy as groundcover in two places.Every spring it get's a radical "haircut".Have been doing that for 6years.Visitors to the Garden always ask:is'nt ivy hard to control?
For me it's not.I garden in zone 6.I like how it looks at the foot of my Stone Benches in the shade.

Graham Rice

I'm in the same position as you, luise h. I planted a couple of ivies as ground cover and they grew well but they will need trimming back in the spring to keep them where I want them.

I think it's important to remember that ivies only flower and fruit (and so spread to new areas when the birds carry off the berries) when they climb a wall or a tree trunk and emerge into brighter light. Sprawling across the ground they never flower and fruit.

Digger Evans

Well I have ivy growing over my side fence and up the house wall, also we have it in a tree in the back garden the blackbirds eat the berries, also I have a fine virginia creeper growing up onto the potting shed, The ivy growing up the house is a lovely sight, if it grows where I don't want it to, I just prune it back, it's not a problem it grows quite slowly and my insurance company hasn't mentioned the ivy at all, the hysteria is undeserved and is probably wasting insurance holders money on a nationwide ivy cull, and the US is a wide country! however I now can expect insurers in the UK to follow suit and condemn ivy as well, my Ivy on the house is "paddy's pride" and it competes with a species montana, right now the ivy is a bit of colour in an otherwise barren picture

Graham Rice

'Paddy's Pride' (correct name 'Sulphur Heart') is not a form of the British native H. helix but of the much larger-leaved and more dramatic H. colchica. Your plant must really sparkle in the winter gloom.

Suzanne Warner Pierot,

There are scientific articles that show ivy does protect walls by shedding water from them, and that it does insulate the walls from heat and cold. The problem with ivy in America is that there is such confusion as to what "English Ivy" is. In the two states (Oregon and Washington) that have problems, it is Hedera Hibernica, the Irish or Atlantic Ivy, not Hedera helix the true English Ivy, that is causing most of the problems. There are many cultivars of true English Ivy Hedera Helix, that are very slow growing and would not cause problems.

There are more than 400 different cultivars of English Ivy Hedera helix. As a rule, the dark green ivies with larger leaves and long spaces between leaves are the fastest and most vigorous. Ivies with small leaves that have compact growth habits (generally sold as house plants) are perfectly good in the garden and will have more tame growth habits. The variegated ivies and miniature ivies are very easy to maintain in the garden. These ivies can easily be kept in check in the garden if pruned once or twice a year.

For more information on ivies go to the web site of the American Ivy Society, www.ivy.org.

Suzanne Pierot, President American Ivy Society

Graham Rice

Thank you, Suzanne, that is so important. The fact that it's not English ivy (H. helix) at all that is causing most of the prolems in OR and WA means that all over the country people are getting worked up about the wrong ivy!!

The USDA plants website (http://tinyurl.com/irishivy) has clearly got it wrong too - they give H. hibernica as growing only in the Carolinas!

Suzanne, the Ivy Society needs to be making a big noise about this - and putting the USDA straight as well.

And thanks for putting me straight.

Genevieve

We have problems with H algeriensis here, I believe. It climbs up our massive redwoods and shades them until they die. Then it spreads to the neighboring trees.

While I appreciate that mass hysteria is never a good plan, there are significant problems with many species of Hedera, and the majority of homeowners are not going to educate themselves on the matter, so I think it is better to help bring awareness to the issue, even when it veers into the hysterics territory, than try and squelch it.

'Cause the thing is, hysteria only reaches those of us who know what we are on about. The masses only get the smallest flicker of a clue that they might want to think twice before planting, which gives nursery workers and landscape professionals a chance to educate them about what works and what doesn't in the individual's climate.

Graham Rice

Well, you have a point in that homeowners are rarely going to educate themselves thoroughly so, as you say Genevieve, nursery workers and landscape professionals have to be aware of the situation so they can give proper advice.

The problem is that the professionals are hardly immune from this hysteria. In fact I get the feeling that in academic circles there's a need to keep stoking up the controversies to generate more grant funding.

In our part of the world the H. algeriensis which is troublesome for you is not even hardy but a column in a local paper urged us not to plant ivies at all.

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