I think it's not just a difference in national cultures, but also in company cultures. I've known companies to send a donation because that is what the family (and therefore the co-worker) asked but would always send a card to the co-worker. It is not uncommon for the family to be traveling very soon and the flowers stay behind and die. I know that the majority of the flowers sent to my family immediately upon a member's death were taken to residents of the facility, so the flowers weren't around for the family anyway. Simply no room for them all, but plants are always good because they last and have less chance of causing an allergic reaction.

One way to find out without the obit is to simply ask the co-worker with the closest emotional ties to call and ask. It's certainly not rude. If all else fails, the boss can call (if they're a good boss).