On Saturday, February 15, 2020 at 9:46:05 AM UTC-5, dpb wrote:
On 2/14/2020 9:57 PM, wrote:
...

Roundup is still just a defoliant more than a systemic herbicide. That
is why you can spray it on your dormant zoysia grass in the winter.

"Glyphosate is a broad-spectrum systemic herbicide and crop desiccant
which acts by inhibiting the plant enzyme
5-enolpyruvylshikimate-3-phosphate synthase. ... Once absorbed,
glyphosate moves quickly through the plant and accumulates in areas of
active growth called meristems. ..."

The only reason it doesn't kill zoysia dead is that it's dormant at the
time.

Similar issues with application at times is hot and dry and stuff isn't
actively growing.

Like most other herbicides, against well-established wood brush it will
undoubtedly take multiple applications or combinations to kill all the
roots so it won't re-establish.

--

You can probably also spray it on cool season grass in the cold of winter
and it won't kill the grass too, for the same reason, the chemical is not
readily absorbed and transported. I know when I decided to kill my lawn
and reseed, I got delayed and didn't apply the Roundup until Oct. Even
though the temps were still moderate, I wasn't counting on how long it
would take for it to kill it and for it go brown. I guess I probably could
have just proceeded to reseed and the old grass wouldhave died, but I
wasn't sure it would kill it. Instead of a week, it took maybe two and
a half weeks for it to go brown.