Patricia Ruggiero wrote:
> Deb wrote:
> On the subject of English Ivy and trees...will it eventually kill
> trees that it climbs into?
> By now you've seen Kathryn's post on this.
> Here are some pieces of info I've picked up from various Internet
> articles
> 1) EI doesn't actually kill the trees into which it climbs; it
> attaches itself to the trunk and branches but it's not taking
> nourishment from these;
> 2) EI can make trees top heavy and/or provide resistance to wind;
> either way promotes toppling of trees in strong winds;
> 3) roots "steal" valuable water and nutrients from the trees and
> other vegetation in the area. This is important to us, here in
> Virginia, during drought years...... 6) am still investigating
> whether EI has allelopathic effects, so as to decide what to do with
> the nice big pile of ramial wood that Husband recently chipped which
> includes vast quantity of EI lately pulled out.
Pat
There is no need for a plant to be an actual parasite taking nourishment
from it victim to eventually kill a tree. I don't think there has ever
been a suggestion though that ivy might be an allelopath.
When one sees how closely ivy can invest a tree, eventually leaving very
little if any tissue uncovered I can't perceive that much different from
wrapping the unfortunate host in a sheath of black plastic. It will be
so thoroughly deprived of light and air I fail to see how it can survive
very long.
Mind you, I suppose you could call the ivy an amateur at this game.
Among trees there is a whole group of professional stranglers which
regularly start life as an epiphyte up in the branches of their chosen
victim, gradually reaching down with special long-range roots, looking
like great thick lianes, till they can establish connection with the
ground and root down, and then multiplying and joining these stems to
form a continuous trunk surrounding the host, to eventually smother it.
After the host dies completely it often rots away leaving a cavity in
the centre of enveloping tree.
I have seen this thuggary being carried out by certain wild Ficus spp in
Africa, and here in NZ we have a very good example in the form of the
Northern Rata. This is a species of Metrosoderos and so a close relative
of our precious crimson-flowered "Christmas Tree" (M.excelsa), which
however has a blameless and exemplary character and makes its own roots
right from the start.
Mind you, the Rata (M. robusta) is eventually an equally magnificent
tree, and even taller, towering over the forest in which it grows to as
much as 25m, but always at the expense of sacrificing a forest tree to
get it going. The flowers can be just as numerous as those of the
Pohutukawa but a lighter rather orangy-red. We are all very fond of it
and prepared to overlook it rather doubtful starting tactics, but it is
unfortunately a really favourite food of our horrible possum pest which
eventually kills even huge specimens by constantly defoiiating them, and
strenuous efforts have been needed in recent years to prevent this tree
becoming extinct. Fortunately a newish policy of trying to keep the pest
numbers right down even though eradication is just not possible seems to
be gradually paying off.
Moira
--
Tony & Moira Ryan,
Wainuiomata, North Island, NZ. Pictures of our garden at:-
http://mywebpages.comcast.net/cherie1/Garden/TonyandMoira/index.htm
NEW PICTURES ADDED 4/Feb/2004
