Don't use RoundUp and don't try to dig out. Japanese maple roots are very sensitive to any disturbance or herbicide and you will risk the health of the tree if you attempt either method. Just snip the leaves off when you see them appear - after a couple of seasons, you will have effectively starved the bulbs and they will disappear completely.

That is why I recommended brushing the leaves. Don't spray. I literally mean get a cup and a paint brush and carefully brush the individual leaves. Habitually cutting the leaves would have the same effect, but could take years. Round-up as a chemical will not damage roots or bark unless you soak the ground with it, but it is always best to be careful, lest you accidentally spill the cup or splash an unintended leaf. The dissolved chemical (Glyphosate) cannot be absorbed through bark, and binds quickly with soil particles, so it is generally not a root risk. It also breaks down very quickly after it is applied. If the chemical is not immediately absorbed through a leaf or other soft tissue, it breaks down into carbon dioxide and nitrogen. Because of this mechanism of operation, it is also an excellent way to get rid of persistent sucker shoots around the base of a tree. The tree will not be harmed, but the proliferation of shoots will be permanently curtailed. Like all things, used sparingly, targeted, and with careful application, it can be an effective time saving tool.

Science:

https://www.biology.iupui.edu/biocourses/N100/goodfor13.html

Cheers,

Werner

Manufacturer propaganda insists RoundUp is not persistent in the soil. Our extensive landscape maintenance experience proves otherwise.

At one time RoundUp was used to spray weeds in tree rings-- no responsible arborist would recommend that now.

And this is a most curious statement-- Round Up will not damage roots or bark--? Actually you can kill a good sized tree stump by simply painting RoundUp on the circumference, altho removing strips of bark is faster. Our favorite way to eliminate invasive mulberries and Bradford pear seedlings!

Just saw this thread, and would go with what you mentioned in the OP above - for next spring I'd just mow or weed eat them down as they come up ( or by hand if the tree roots are in harms way), repeat once more next spring and that should do it. Being that the daffs have been in the lengthening hours of shade under the expanding maple tree they should be weak enough to kill through physical means and some time.

No fun killing things like you said, we went thru that bit of guilt digging up an aged asparagus and strawberry beds last year. They both had a good 14 years....but we won't miss all the bending over picking them!

Thanks so much for your post!