Get out the microscope, because we’re going through this poem line-by-line.
Though worlds of wanwood leafmeal lie;
And yet you will weep and know why.
- With these lines the speaker continues the same sentence he started in lines 5-7: when Margaret is older, she won't "sigh" over dead leaves, even if whole heaps of them are lying at her feet.
- More made-up words occur in this line. "Wanwood" just means dead leaves or bark, but it also suggests sickliness and disease ("wan" means "pale").
- "Wanwood" also sounds like "wormwood," which is a kind of bitter plant used to make absinthe. Poets sometimes use the word "wormwood" to describe anything that tastes bitter. Hmm. Now why would dead leaves make you feel bitter?
- And "leafmeal" means that the dead leaves are lying in a scattered, disorganized way, kind of like the word "piecemeal."
- The repeated "w" sounds in "worlds of wanwood" and the repeated "l" sounds in "leafmeal lie" make for some excellent alliteration.
- The speaker says that, even though Margaret won't cry over whole heaps of dead leaves when she's older, she will still "weep."
- The exact meaning of "know why" is ambiguous at this point. Perhaps the speaker is saying that, in the future, Margaret "will" "know why" she's crying. That would be the most straightforward reading of this line. But it's not clear whether that helping verb "will" goes with "know" or just with "weep." So "know why" could be an order (what grammar teachers call the imperative). In other words, the speaker could be saying, "all right, Margaret, you need to hear this. Listen up! Know why!"