Well, it's a lovely inventive scene!
The weeds at the base of the stone wall look good. As for the others, I suspect the problem is that you haven't yet looked closely at weeds. The problem with inventing anything on-the-fly is that you only have images stored in your mind to work with. So those images need to be fairly comprehensive.
When the weather improves later this year, take a sketchbook out into the countryside and randomly choose leaves of weeds to draw. You don't need to draw the complete plant, just interesting leaves. At the same time, look to see if they are growing in pairs from the stem (opposite) or are staggered (alternate). Now when you invent weeds to draw, you'll have those leaf shapes and growth patterns to draw on.
I have a couple of problems with this drawing, if I may?
ANDREW-Weeds1.jpg
THE STONE WALL AT THE LEFT
I'm seeing this as a low wall with a header course, that then continues upwards, but not quite as wide.
If the upper part is meant to be
behind the lower part, then you need to show that. That's easier said than done

, but I think I'd make certain the blacks in the lower half were darker, the edges a little sharper, and the stones possibly a little darker too. That would exaggerate the recession a bit, but there is hardly any recession present, so a little exaggeration might help.
And the top half worries a bit because its edge is remarkably straight. To my eye, the end of the lower part is more realistic.
I love those two birds on the wall!
THE GRASS
This is working well at the base, but somewhere around the girl's waist, I seriously doubt you'd see any detail at all. It's not easy to explain, so take a look at my "Spinney Lane End" for grass recession:
ANDREW-Weeds3.jpg
I'm not claiming it's the answer to everything, but it does contain two or three different ways of drawing grass at various distances, and they all merge into each other as your eye travels back. At the base, there is negative drawing (the dark spaces are drawn to expose the grass - as you've done with the weeds). In the middle it's positively drawn grass (the leaves are drawn, not the spaces), and in the background it's just the bands of shadow you'd expect to see, with no detail at all.
THE AVENUE OF TREES
Is that what this will be? If it is, I fear it's either too small or too low. The trees have the shape and feel of something BIG - not low bushes - yet...
ANDREW-Weeds2.jpg
The nearest tree is closer to us than the stone building at the left. Let's say the steps up to that building are nine inches high (23cm), so the total height of the steps is 28" (71cm)... the second tree back in the left-hand row, which is directly opposite those steps, is only 60" (1.5M) high. Just to check, I added convergence lines from the VP. If the girl is 5 feet high, so is the tree.
Or maybe I'm completely misreading your intention...

In which case I apologise for making assumptions. Everything else is looking gradely and grand, as they say around here.

And you're obviously enjoying yourself, which what really matters.