Mow and then cover the area with clear plastic. According to my horticulture prof. the resulting greenhouse effect it causes will kill everything and sanitize the ground. (Though we were in Texas at the time, YMMV)
I was thinking of different ways to get Roundup on the shoots only and not the grass. Using a brush, or sponge, but never thought of the pan method you mentioned! But when there are so many shoots, it becomes a daunting task.
Mow and then cover the area with clear plastic. According to my horticulture prof. the resulting greenhouse effect it causes will kill everything and sanitize the ground. (Though we were in Texas at the time, YMMV)
That's why you bend them down into a shallow pan of roundup and let it be localized (or brush / wipe it on the leaves to keep it off the grass). It will not harm the grass if it doesn't touch the grass leaves. It's soaked through the leaves and then kills the plants from the roots up.
You don't need to get all of the shoots....just a bigger one on each localized root. Kill the main roots, kill all the shoots.
Had a similar problem at my old house. Parents killed it once, cut it down to an inch of stump then my dad drilled a wide shallow hole and poured diesel(!) in it. It then grew about 10ft away in the fenced alleyway where the AC compressor was, between our house and the neighbors. It was originally a thicker tree, but after they killed it, it came back as two smaller, thinner trees.
We had originally tried to kill it because it was growing into the power lines and pulling the fitting where they connected to the house loose, and it was getting expensive calling out the power guys all the time to fix it.
Your method is pretty clever and while it is resourceful, I cant see myself filling and maintaining 100s of little pots all over the front yard. Every week, we get 50 - 100 new shoots, less in the area I've rooted and dug up.
Brushing on the leaves may be the next step I try.
Goats LOVE all varieties of maple trees. I just fenced in a couple of acres for the goats. There were dozen, if not hundreds of small trees up to 3 or 4 feet tall. The goats ate those first, long before they touched any grass (and wild grape vines - both are like candy for the goats.) If your yard is fenced in, get a goat for 2 or 3 weeks. It'll turn those weeds into fertilizer for the grass.
I used to have the same problem with sumac trees. I cut down 10 or 15 of them, and before I knew it, I had hundreds of them. I'd pull the new ones out by the roots. For every one I pulled out, 3 would grow back in its place. After a couple years, I added goats to that area. A couple weeks later, zero sign of the sumacs even trying to pop their little stems out of the soil.
I love lurker posts like this. In to save the day!
Be warned, if you do the roundup applied to the leaves trick, it will also kill grass in a small area around the saplings.
I had a Johnson grass in my yard. I read that the best way to kill it was to apply roundup to the leaves.
I used a sponge and was careful to only wipe it on the leaves.
A week later, I had 100 brown spots in my yard, about 6" in diameter.
They finally filled in, but it looked bad for the rest of the year.
I would just keep mowing it. There is no way they grow faster than the grass.
In your OP pics, how long had that been since you had mowed?
The tree will eventually run out of energy.