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?