The cherry blossom front.

I've been thinking about the first tanka we wrote in 習字. It seems to refer to a very specific moment in a cherry tree's life cycle, and I've never quite understood it:

薄紅に葉はいち早く萌え出でて咲かむとすなり山桜花 

The part that always really confused me was "sakamutosunari"—must have something to do with blooming, but what? 先生 explained, but I'm slow and still don't get it.

Today I happened upon "-mutosu"—a verb ending that means to be trying to do something, or to be just about to do something. With the usual なり ending (である？), that makes sense! 咲か-むとす・なり.

薄紅に
usubeni ni
pinkly

葉はいち早く萌え出でて
ha ha ichi hayaku moeidete
leaves sprouting quickly (early, too soon?)

咲かむとすなり
sakamutosunari
they're just about to blossom—

山桜花
yamazakurabana
(flowers of the) mountain cherry trees

I don't know much about plants, so I still don't quite understand how the leaves are blooming pinkly (rather than greenly), or whether the leaves are just coming out or are out too soon. Maybe em dashes will help:

pinkly—the leaves having sprouted too soon—
they're about to bloom, the mountain cherry trees 

いち早く also is confusing me—is it that they'll bud soon, or that they've budded too soon? If leaves precede blossoms, whence the pink? Clearly, in the future I'll have to pay more attention to the sakura in Fairmount Park, and not just on Sakura Sunday.

I love that the media in Japan track the "cherry blossom front" (桜前線), the blooming point of sakura up and down the country. It's a really fun idea, and here in the US we have nothing like that.