Re: grass clippings as mulch
Good morning, Middle Earth Gardeners
Being new on this list, may I introduce myself, Peter Lewis, Cambridge UK, the
nearest thing to Med. area in England - anmd quite close to the real thing. We
are in the driest part of Europe north of the Pyremnees, 50 cm rainfall, and a
lot of sun. We grow many Med. plants - Olives, Oleanders, Lemons, Callistemons
etc etc. with success, so long as we take some cunning measures over winter.
When we plant tomatoes, we plant a long-tom pot beside them, and only water
them through the pot. This tends to drive the roots down rather than them
scattering over the surface as they would like to do. It may be unnatural, but
it works.
Thanks for the space.
Peter Lewis, UK
Jerry Heverly wrote:
> At 10:05 AM 6/29/99, Damian Martin wrote:
> >Dear Med-planties,
> >
> >Can anyone comment on the relative benefits of raw grass clippings as
> >mulch?
>
> Let me introduce another concept, one that many of you may be familiar
> with; allelopathy.
> Everyone knows that the leaves of *Juglans* species contain toxins
> injurious to other plants. It's a readily understandable genetic advantage
> for one plant to be able to suppress the growth of potential competitors
> for scarce nutrients. A researcher at the University of Rhode Island in
> the States in the 70's discovered that one of the most potent allelopathic
> producers were cool season grasses; rye, bluegrass, fescue, et. al. and
> that the most common effect of these allelochemicals was on woody
> plants......
>
> I have recently lost some newly planted Celtis
> >australis
>
> I used to take classes to local places where, by chance, architects had
> designed in bunches of trees, some in turf, some in bare soil. It was
> always an eye-opener. There would be a line of trees, all obviously
> planted at the same time, yet the turf-encumbered trees were generally half
> the size of those in bare soil. Competition accounted for some of the
> difference but allelopathy produced most of the contrast. The grass was
> clearly secreting substances (still unidentified) that were killing
> roothairs of trees. The same effect can be observed if you grow several
> trees with varying amounts of grass-free areas maintained at the base of
> each tree. The bigger the grass-free patch the faster grows the tree.
>
> I should add, however, that allelochemicals are highly soluble. I.e., the
> harmful effects usually leach away after a couple waterings. *However*, if
> one were conscientious and adding new clippings all the time you could
> easily kill off a young tree.
>
> Ironically turf allelochemicals are a public hazard in the US. California
> passed a law some years ago mandating that municipalities reduce their
> waste stream by 50% by the year 2006(I confess I'm vague on those numbers,
> someone more knowledgeable should correct me) and the principal target for
> most cities has been lawn clippings. Not only do they form one of the
> largest components of what people throw away but they poison waterways with
> concentrated leachates. Most counties in California have funded public
> agencies designed to encourage backyard composting; again the idea is to
> reduce waste, especially, ta da, lawn clippings.
>
> >Damian Martin
> >Talavera, Central Spain (hot dry Summers, cold Winters)
