Re: Eucalyptus Questions
I'd like to pose the same question in reference to cypresses. Since they don't
have a canopy the same answer probably doesn't apply. What is it about them
that discourages surrounding growth?
Cali Doxiadis
Margaret Moir wrote:
> ----- Original Message -----
> From: Glenn Breayley <valhalla@iafrica.com>
> To: medit-plants <medit-plants@ucdavis.edu>
> Sent: Wednesday, March 14, 2001 3:42 PM
> Subject: Eucalyptus Questions
>
> > While on the subject, does anyone have the answers to the following
> > questions.
> >
> > 1/ Are Eucalyptus leaves & compost truly poisonous to underfloor plants ?
> > Might not their bare floor areas rather be due to their superior water
> > robbing capabilities. ?
> >
> > 2/ Does anyone have any knowledge of the Jarrah ( E. marginata ) being
> grown
> > commercially outside of Australia ? Being one of the worlds greatest &
> most
> > durable of timbers I was wondering if it has commercial possibilities.
> >
> > Regards
> >
> > Glenn Breayley. Ragnarok & Valhalla Research.
> > POBox 26158, Hout Bay, 7872, Capetown, South Africa
> > Ph/Fax SA 021 7904253 E-mail valhalla@iafrica.com
> > Wholesale nurseryman & Tillandsia specialist wholesale & retail grower.
> >
> Glenn, I don't believe the leaves themselves, once parted company with the
> tree, have any toxic properties at all. In common with many other species
> many of them are allelopathic, and the canopies may also have a "toxic
> drip"........rain leaches a chemical from the canopy that is a growth
> retardant to other plants. This is not universal with all eucalypts, mostly
> just the ones that have to be super-competitive in their own environments.
> Your surmise, that like a lot of trees they drink a lot of water and
> out-compete other plants is frequently the case when no allelopathy is
> present.
> The WA Jarrah/ Marri/ Karri forests are the overstorey for thousands if not
> millions of plants, growing densely underneath the trees, no toxins there.
> But once a tree is mature, it is almost impossible to get things back in the
> understorey if it has been lost thro' grazing or whatever. However a fire
> will release nutrients trapped in the humus and leaves and provide an
> ash-bed that the re-generating plants can germinate in.
>
> The reason the leaves are resistant to being composted is because they're
> sclerophyllous and have a very hard waxy coating to make them resistant to
> transpiration. If the leaves are chopped up, such as through mowing or a
> mulching machine they break down much more quickly. In combination with a
> high nitrogen plant matter such as lawn clippings, they can make a great
> mulch/compost. Eventually, even if entire, they will crumble to a superb
> leaf mould but in the natural environment this is much hastened by fungal
> associations.
>
> Jarrah? It's never been attempted as forestry plantings......the tree is
> much too slow growing to interest any foresters. Probably about [this is
> just a rough guess] 200 years old before millable.
> Margaret.
> Margaret River
> Western Australia.
