"Stems and seeds" refers to the hodge-podge of loose change one has prior to being COMPLETELY broke. To clarify, 'stems and seeds' are NOT the huge containers of change that people gradually compile; rather, the term applies to the usually worthless (i.e., mostly pennies) coins you're down to right before payday.
"Anyway, we stopped to grab a draft on the way home from work, like we usually do. Dumb-ass me forgets I'm broke,
and I order the first round. At the exact moment I saw the barmaid turn the corner with a trayfull of tall-boys, it finally dawned on me that I was down to my 'stems and seeds.'