"paghat" wrote in message
news
In article , "Stephen
M. Henning" wrote:

"Doug Kanter" wrote:

"Stephen M. Henning" wrote:
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.

Really? Even 5-6 feet away from the shrubs themselves?

It depends on the spread of needles or scales. The chemicals are
released from the needles or scales. If they get scattered around, then
the toxic effect is scattered around.

But additionally plants like junipers sometimes grow in hard compacted
organically depleted & dry soils that little else can get a foothold in.
If the whole area had its soil loosened & some peat worked into it, & a
bit of water gotten to the improved soil, there are a whole host of plants
that actually thrive in the environment created by junipers or walnuts &
other trees & shrubs that exude growth-retardants -- such as virginia
creeper, daffodils, grape hyacinths, daylilies, cranesbills, sweet
woodruff, & a god's plenty of weeds.


I agree with this. Once you kill off all the perennial weeds and let the
soil surface crust over, weeds just don't grow. If you break-up the surface
and mix in some organics to prevent it from crusting over, all kinds of
weeds will grow.