permaculture

[Rick Valley <bamboogrove@cmug.com>]

Robyn says: 
>> 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.

And John S. replies:
>> 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...

I'd guess it's the shallow, hungry, thirsty roots. I've noticed the same
phenomena with bamboo next to Lombardy poplars; Robinia is not stunted at
all. The description of the corn fits moisture stress.
I was impressed by the monster circular saws they have for tractors in NZ
for cutting roots of Lombardy poplars and Matsudana willows in their
windbreaks, so the crop yields don't suffer.
-Rick