He know what it means. And he's said it before, half-heartedly, in the context of me saying it to him. But this afternoon, while eating a snack, Seth looked across the table at me, stared me right in the eye, and said "Mommy, I love you." He ran around the table and climbed onto my knee and hugged me fiercely. He said it again with his face buried in my neck. He meant it.
I guess I know how which flower petal I'll pull out last this time!