No, generally a wall is not the same as the ground
Grasping weeds and vines sprout from the ground in a 20-foot square starting from a point within range.
The rules do not define what the word ground means, which means we use the common English definition:
the solid surface of the earth.
Thus, according to the rules as written and common English definition, a traditional manufactured wall is clearly not ground.
As Jeremy Crawford has said:
Saying that a wall is the ground defies the idiomatic meaning of the
word "ground." But a DM is free to allow bonkers things.
Which leads me to my next point...
...But many cases may come down to a DM ruling
However, there are definitely edge cases here. For example when you are falling down a pit dug into the earth. Or alongside a cliff face. However, these are edge cases that the DM must decide since they can go either way and the rules are vague.
If your DM is willing to accept an even more lenient view of what ground is, they could even extend the definition to include things like walls and structures. However, this would be a houserule at your table. It also has the potential downside of making the spell potentially a lot more versatile than the designers intended. After all, if walls could count as ground potentially any solid surface could. If your DM is fine with this though, it is within their power to rule it as such.
As Jeremy Crawford has also said:
The DM decides how generously to interpret words like "ground." Unless we redefine or focus a word, we use it in its idiomatic English sense, knowing that some words are open to creative interpretation.
It is important to note that there are other spells that also must be cast on the ground so a DM should consider carefully before allowing it for all.