Seems like glyphosate doesn't do very good on anything woody, also I don't think it's suppose to. But if you cut something off and douse it in glypho it seems to do a pretty good job killing it..
What's some plant examples it won't control, just curious?
Historically, glyphosate has been considered a "non-selective" herbicide. When ROUNDUP entered the market in the late 70s, it was a "miracle product" - and a virtual gold-mine for Monsanto. No other
systemic,
non-selective,
soil-inactive herbicide existed at that time. Off hand, I can't think of a comparable herbicide-chemistry that exists even today.
However, "non-selective" may have been an overstatement to some degree. Many vine species, including poison ivy, are very tolerant to glyphosate. Sedges (nutgrasses) are another tolerant group. With some tolerant species, the above-ground portion of a treated weed may turn yellow or "brown-out", but the roots or tubors remain viable and can quickly generate new growth - usually requiring repetitive treatments to "maintain control" (< industry-lingo meaning "treat it again"). In many cases, a
product's label will recommend a tank-mix companion-herbicide to provide better control of tolerant species.
Glyphosate actually works fairly well on several woody species (foliar-applied, usually at relatively high concentrations) - but will not work at all on others. With woody species (and even perennial weeds), application-timing can make a lot of difference. For instance, several willow species and Chinese tallow trees (aka "chicken trees" in LA) become susceptible to glyphosate in the fall (after seed-set but before leaf-color change). As mentioned above,
"Hack-n-squirt" and cut-stump treatments broaden the spectrum of glyphosate-susceptible woody species - but it still isn't a 100% bet for full "root-kill" control. There are other herbicide-chemistries that usually perform much better than glyphosate for this purpose.
A concerning issue with glyphosate over the past several years is the rapid development of
"resistance" within weed-species that were previously susceptible to this chemistry. These resistant species usually occur in farming regions due to decades of glyphosate's repetitive use - especially at low and often sub-lethal rates (farmers shaving $). Basically, members of a weed-specie that survive a low-rate glyphosate treatment pass along their genetic tolerance to the next generation. Several successive generations later, the resulting progeny become increasingly tolerant or completely immune to the herbicide. The same concept applies to insecticides, fungicides and even pharmaceuticals - which is why many antibiotic prescriptions admonish the patient to finish the entire prescription (otherwise, any surviving pathogens may pass along their elevated genetic tolerance to the next generation - and subsequently render the antibiotic useless). This is why it is advisable to rotate the use of different pesticide or antibiotic classes (modes of action), to avoid tolerance-magnification toward a single chemistry's mode-of-action.
I catch myself rambling - so I'll shut up. Did this answer your question - or was it gross overkill?
