Ivy IS a real problem

[Mick Dempsey]

I mentioned this before, it was David Humphries who pointed it out on here but it’s clear once you understand.

 

Ivy doesn’t engulf the crowns of living trees, it stays just underneath.

 

How or why I know not.

 

 

[Haironyourchest]

This it it. Healthy canopy, not much light for the ivy, and not much water either, in the dry spells, as the tree will out compete it. If the tree is poorly, the ivy will have a larger share of water, nutrients and light. At some point, the balance will shift in the ivy's favor. So it's fine, it essentially hastens the demise of genetically or otherwise sub-par trees, and also replaces them as habitat. Probably helps them rot quicker too.

[Guest Gimlet]

There you go. Ask a reasonable question and you get more sensible answers in four posts than toy chucking achieves in four (or was it five or six...?) threads. 

[Dan Maynard]

I have read it starts off growing away from the light, which pushes it under the tree canopy. At some point in maturity it switches to growing towards the light, and then climbs up and away. I'd have to find the source again.

[sime42]

I have read it starts off growing away from the light, which pushes it under the tree canopy. At some point in maturity it switches to growing towards the light, and then climbs up and away. I'd have to find the source again.

I've read that too. In theory you can use ivy on a tree to deduce the direction of North.
I can't quite remember the name of the book but I think it may have been this one;-

Waterstones

WWW.WATERSTONES.COM

---

[scottythepinetree]

I live in the West of Ireland. We're absolutely covered in the stuff. It's everywhere and has been for as long as I can remember.

If you have a tree that you're particularly fond of or want to look nice, sever the ivy every few years. No dramas at all. Same as it has always been.
 

If you were really stuck for a research topic, I bet you could get some mileage out of this. Canvassing a group of tree surgeons on a forum probably won't add much to it though.

[scottythepinetree]

16 hours ago, Dan Maynard said:

I have read it starts off growing away from the light, which pushes it under the tree canopy. At some point in maturity it switches to growing towards the light, and then climbs up and away. I'd have to find the source again.

Any chance you could find that source? I wouldn't mind taking a look at it. Provided it isn't an out-of-print edition of a 30-year-old book that costs multiple hundreds of £/€ of course.

Edited April 26, 2022 by scottythepinetree

[Guest Gimlet]

I wonder if it "knows" when a tree is dead. It would be to the plant's advantage to single out a dead host tree if it can, so it isn't wasting energy climbing something it will have to compete with for light. Which goes back to my earlier mention of elder. You rarely see a living elder that's been colonised by ivy, but equally you rarely see a dead one that isn't engulfed. 

Is it just pot luck that the ivy picks a dead one and then capitalises? Or is it in some way attracted to dead ones? If it were just pot luck, you'd expect to see more partially colonised elders. 

It's known that most climbing plants are stimulated by a chemical trigger to climb when they contact a likely host. Could that chemical trigger also identify whether the host is alive or dead?

Edited April 26, 2022 by Gimlet

[sime42]

Any chance you could find that source? I wouldn't mind taking a look at it. Provided it isn't an out-of-print edition of a 30-year-old book that costs multiple hundreds of £/€ of course.

I think I read about it in this book;-

The Walker's Guide to Outdoor Clues and Signs : Tristan Gooley (author), : 9781444780109 : Blackwell's

BLACKWELLS.CO.UK

---

Readers may be familiar with such things as natural weather forecasting, basic tracking and natural navigation, but this guide will reveal intriguing new lesson

[Dan Maynard]

4 hours ago, Gimlet said:

I wonder if it "knows" when a tree is dead. It would be to the plant's advantage to single out a dead host tree if it can, so it isn't wasting energy climbing something it will have to compete with for light. Which goes back to my earlier mention of elder. You rarely see a living elder that's been colonised by ivy, but equally you rarely see a dead one that isn't engulfed. 

Is it just pot luck that the ivy picks a dead one and then capitalises? Or is it in some way attracted to dead ones? If it were just pot luck, you'd expect to see more partially colonised elders. 

It's known that most climbing plants are stimulated by a chemical trigger to climb when they contact a likely host. Could that chemical trigger also identify whether the host is alive or dead?

Plants are sensitive to chemical triggers, I guess alive or dead should be really easy to tell from water content or how much water vapour is around the plant so yes absolutely plausible it responds to the host being dead.