Elmo wrote:
How does weed killer get INTO the plant (leaves? roots? stem? mechanism?)

After cutting a 500-yard long path through thick poison oak, I'm now
applying huge amounts of glyphosate-based Roundup weed killer to kill
remaining emergent plants left behind after the battle.

These constant skirmishes are depleting my Roundup, gallon by expensive
gallon (bought in concentrated bulk from Costco).

I'm spraying the stems, the ground, and the leaves ... but ... I wonder ...
what is the mechanism that allows UPTAKE of the glyphosate?

I looked up how weed killers kill, and can easily ascertain that
glyphosates mimick the natural EPSP Synthase needed as a catlyst for the
plant to create proteins ... but nothing I've found so far tells me how the
glyphosate is ABSORBED into the plant and WHERE it is best applied
(leaves?, stem?, roots?).

Mostly, I'm left with huge tangles of poison-oak stems ... so I ask ...
WHERE does weed killer get INTO the plant and how?


The label will give you the simplest answer. Bear in mind that
herbicides have different modes of action. Pre-emergents, used for crab
grass-type weeds (atrazine, etc.) are taken up by roots. Timing is
critical.

Broadleaf herbicides, like Weed B Gone, are taken in through the leaves.
It's been a while, but Weed B Gone worked wonders on the weeds in
our southern lawn. There are lots of combinations and mixtures sold
these days, and a lot of overuse because people don't maintain lawns
properly or apply chemicals properly.
The instructions for WBG are important....weeds must be actively
growing, don't apply if rain expected, etc. When we used it on our
lawn, we fertilized a couple of weeks in advance so everything was
growing and avoided using it during hottest weather when grass is stressed.

With tough weeds, it is easier and safer to cut the plant down, wait for
new growth to appear and then use Roundup or similar vegetation killer.
One especially nasty weed is asparagus fern...one of many house plants
that idiots like to plant outdoors...that is invasive in Florida. It
has loads of berries and huge, tuberous roots that make it impossible to
dig up when it takes root in hedges. I crawled around under our hedges,
cut the asparagus fern and ivy to the ground, waited until they had some
new growth and sprayed with Roundup. Using this method, you don't hit
the desirable plants and you don't need to use much Roundup. Logic
tells one that a plant can't thrive without leaves and if you cover all
of it's leaves with suitable herbicide, it will be effective. Some
tougher plants, especially stuff with waxy leaves like ivy, are more
susceptible this way because the new growth is more tender but might
require another application.