I have a few plants onboard, and I kinda dig them. I sail with them too... usually one sits in the beer holder by the wheel. They are indoor plants, and my rule is unless I'm mid-project, I want to be ready to sail in 20 minutes or less... so the plants have a place.
I think I'm going to make a planter that resides on the post that contains the cable for the centerboard. It'll be right under the leaking deck hatch
, so it'll stop the rain from getting on my table.
One of the plants on board right now is a cactus... I can advise you against having a cactus on a boat (completely not my idea, and I threaten to teach the thing to swim everytime it bites me)! But it has character.