sluggish dazed spring approaches (lines 14-15)
This is the beginning of the change. Up to this point, everything has been lifeless and still. Nothing has changed in the landscape. Now, something new is coming. The transformation doesn’t happen all at once. Williams points out that spring is still sluggish (talk about a word that sounds like what it means!), but things are waking up.
Now the grass, tomorrow the stiff curl of wildcarrot leaf (lines 20-21)
Next, Williams describes the change actually happening. It goes in steps, one thing after another. Some grass today, a few leaves tomorrow. We know in our heads that spring is here; it’s been introduced, almost like a character in a play. But, now, we actually get a description of spring, of how the transformation begins and continues.
the profound change has come upon them (lines 25-26)
He lays it on the line here. This transformation is definitely the big event of the poem, its reason for existing. It’s kind of mysterious, too, though. We see spring coming, but we don’t really know what it is. It isn’t something the plants do, it is something that "has come upon them." Where does it come from? Is it in the plants? Does it arrive from outside? Williams tries to make us see spring happen, but he also tries to make it seem strange, to make it harder for us to take it for granted. He wants us to know that it is profound and magical, but also sort of foreign. We can watch it happen, but what do we know about the thing itself?