permaculture

["John Schinnerer" <john@eco-living.net>]

Aloha,

Could your observations be due to poplars' extensive and aggressive root
systems combined with their generally thirsty nature?

This is the first indication I've ever heard that poplars have
allilopathic properties...where is this documented?  PFAF doesn't mention
it...


> Beware of allelopathy with poplars....
> I saw a poplar windbreak in New Zealand, there was a farm track between
> the trees and the farmers field  of sweet corn - the allelopathic impact
>  of the poplars was the most dramatic visual example I've observed yet.
> Near the track germination was sparse and plants severely stunted
> (barely  18 inches high), the density and plant size gradually and
> uniformly  increased with increasing distance from the trees and at 1
> and half times  the hight of the poplars into the field the plants were
> dense, lush and  over 6 foot high. The sunflower crop on the other side
> had exactly the  same phenomena. It was interesting that the most
> stunted section was  within the height of the plant horizontal section
> and plants rose in a  J-curve to the 1.5xh point.
> I'd be rather cautious to use poplars in a productive cropping system
> especially vegies. Poplars are fine in grasslands and agroforestry
> systems, don't have the same allelopathic relationship with grasses and
> clovers quite like growing under them.
> Robyn
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John Schinnerer, MA
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