"Pam - gardengal" wrote in message
news:kK7Tc.301797$XM6.35745@attbi_s53...

"Stephen M. Henning" wrote in message
news
"Doug Kanter" wrote:

At my apartment complex, there are long
stretches of flower beds where the only thing growing is the usual
generic
evergreens.

Many of these "generic" evergreens shed needles (or scales) that are
preemergence herbicides and prevent weeds from coming up from seed. One
good examples is juniper Virginianis. That is why some forests have few
weeds on the forest floor.


This is not exactly true - allelopathy is not exactly the same as a
pre-emergent herbicide, although the effects can be somewhat similar. And
the lack of weeds or significant undergrowth in heavily forested areas is
most often due to competition of the larger root mass of the trees for
nutrients and soil moisture combined with persistant shade from the forest
canopy. In more open areas, weed and native growth is generally pretty
prevalent.

The lack of weeds in this case is probably a combination of factors.
There
are some pretty heavy duty herbicides out there which are commonly used in
the maintenance of commercial properties plus many wood-based mulches have
allelopathic properties of their own, albeit small and not very
longlasting.
Also, many pre-emergent herbicides can have a rather longlasting effect -
upto about 9 months. That combined with the fact that most common weeds
seed
in fall or spring (but not in summer) can account for the fact that you
haven't seen any significant weed development yet.. If no further spraying
is done this fall, I''ll bet you see some weeds start to develop with the
fall weed crop and the autumn rains.

pam - gardengal



Hmmm. I'm glad I didn't plant any herbs or vegetables there.