My experience so far: Once hit Poa trivialis and all other grasses are toast (rarely KBG returns from strong rhizomes). I have blanket sprayed areas that have been fallow for over a year. Poa annua has sprouted there and a lot of weeds, but never have I seen Triv there again. If the lawn is very dense and the blades are covering each other, a second (and third) application may be appropriate.

I recently brushed some Triv with glyphosate and tried to paint only a few leaves at a time so that the surrounding grasses would not be damaged. Futile effort. Although I used only a few drops, it almost looks like I sprayed everything. Today I found more Triv partially on the edge of the dead spots. I think that is the reason for the reappearance: Some Triv have been overlooked. Or introduced by reseeding.

I was actually going to cut out the infested areas and replace them with a specially created replacement lawn, but I have now found Triv in those as well (more about this in another topic).

 

Timing - When the plant is actively growing and not stressed by mechanical or chemical injury. It should be well watered and happy with the weather/temperature for a month.

It is better to spray again when the plant has stopped responding to the herbicide (as in trying to grow again). At this point it is weak and beginning to regrow (in a favorable environment). Most herbicides will have this time listed as 2-4 weeks.

The recommendation is pretty common on most professional herbicide labels because that is how systemic herbicides work. If you want a kill, it only works when the plant is moving the chemical through the plant. If/When you apply something that stops this growth, applying more or early doesn't help as much and tends to be a waste. It also is advised not to pull weeds as the goal is to keep the ai in the plant and affecting the roots. If the plant is pulled, there is less leaf tissue for the ai to be absorbed by on a following treatment and the roots might be able to survive and grow another day. The following treatment is likely only to work when the plant is using up stored energy to create new growth. The best time to reapply is when you see it trying to grow anything green again - to introduce more into the plant along whatever new path(s) it created or is using to survive.


I have successfully painted leaves of Quack grass growing inside of bunch of ornamentals with successful kills. After about 2 weeks, it finally turned brown, and I ended up just pulling it. Never came back in the same area.

I have also killed off established Bermuda grass without Glyphosate. It takes 3-4 applications/months, but you can't do it in a season because as you slowly kill it, you have to wait for favorable conditions (regrowth) to treat again. This usually means it actually takes 2 seasons (maybe 3) to fully remove Bermuda grass (without full renovation/solarization/glyphosate).

 

Green, hopefully AI will give us answers!! I don’t think timing of the gly app is the issue. Cole Thompson’s research said spring but that was not at all conclusive.

My experience with multiple reno’s in late summer: 3X gly apps 2 weeks apart with plenty of water in between. First year post reno showed no obvious signs of triv. Year 2 had a few spots. Year 3 a few more, etc.

I’m on about year 5 or 6 and probably need another reno given the amount of triv. The spots are like salt and pepper through the yard. My conclusion is that it’s coming from seed. The plant does seed despite claims to the contrary. I find it germinating in the cracks between my brick patio. If it comes back from viable stolons after roundup then you would expect it would come right back in year 2 and would not germinate on a patio…..

 

My conclusion is that it’s coming from seed. The plant does seed despite claims to the contrary. I find it germinating in the cracks between my brick patio. If it comes back from viable stolons after roundup then you would expect it would come right back in year 2 and would not germinate on a patio…..

I agree with this. My recent experience suggests that seed plays a major role as well. I recently used a sod cutter to cut out triv spots. I cut it about 2 inches deep to make sure I got it all. I left it bare in a few spots while I waited for sod to arrive, and a few triv plants actually returned in the bare spots within a couple weeks. My only conclusion was that it came from seed in the surrounding areas (neighbor's yard)..unless 2 inches wasn't deep enough.

 

I really need to do some tests with the seed. I have Triv seeds from my lawn. Just have not tried growing them yet.

But let's not diverge from the original topic too much. We can start a new thread on seeds.