What I do have under there is either yellow rag weed or something very similar that blooms in the fall and gets blamed for making everyone for miles have hayfever, if I don't "do something", and wild blackberries which are indestructible and make weeding harder.

On the weekends, I usually get up and put the dogs out and then go back to bed. Today I weeded that ragweed stuff a while. Right now, it hasn't flowered so it doesn't make anyone sick. it won't flower for 2-3 months.

I'm thinking in a few weeks, when I have more money, to ride through the flowers on the riding mower to get in there, mow all the 'ragweed' all flat, and put down something indestructible that would still let the tree have water. No idea what this magic substance is, but I think I need some.

What should I use?

It blooms at the same time as ragweed & gets the blame for making people sneeze, but really it's the ragweed's fault.

I don't disturb goldenrod in my garden.
It makes a beautiful, brilliant yellow punctuation mark when everything else is ho-hum boring.

I wouldn't bet on anything voluntarily spreading toward shade & away from sun;
most plants would migrate toward the sun, out from under the tree canopy.

Beneath & around my weeping willow right now, there's some tough coastal bermuda grass (the stuff they bale here in Texas to make hay!) & a few Mexican Primroses.

Little by little, I'm weeding out the bermuda & leaving the wildflowers.

Once every summer, I cut them back, & they always bloom the following spring.

Any area not colonized by the Mexican primrose can remain bare, covered with a thin layer of mulch.

If you don't like the look of mulch, & you don't want Mexican primrose, you might use English ivy, vinca, or some other low-maintenance, shallow-rooted groundcover.

Coleus is beautiful & colorful, but this is the first year I've used it:
I'm *thinking* it freezes in the winter & you have to take cuttings & keep them on a sunny windowsill all winter & then re-plant it in the spring.

Best luck!

sylvia

(ps:I think we gardeners fret ourselves silly over what'll grow under a tree:
the tree doesn't want anything under there drinking up its water, & most plants don't want to be under the tree, anyway.)