Having permanent green plants on board is a different thing when doing long distance cruising, i.e. bringing your local plants across the seas and oceans to other continents or countries.
In most countries Customs, Immigrations or other agencies in charge for the fresh green perform a rather strict law about the import of fresh fruit, vegetables and plants. Most times the authorities are not amused when you carry these on board and you come from far away regions.*
Reactions were: leave it on the boat and make sure that it does not get ashore (as waste); Declare all fresh green (including plants) and hand it out as we will destroy it; Don't even think of having any fresh green on board when entering national waters!
Friends of us carried an Aloe Vera
(Medical Aloe) on board on their way around the world. Most times it was no problem to have this living plant on board, but there were some occasions that the authorities insisted that it had to be disposed of properly. Well, they were able to keep it after they convinced the authorities that this special plant should rather be seen as a medicine.*
*Other reasons that makes it not easy to keep plants on board are the harsh environmental conditions they have to live in. Just imagine the temperature changes in the cabin, as most boats do not necessarily have air condition on board. They use water. They bring additional moisture due to evaporation into the boat, a thing we do not really want to have in higher latitudes.
Considering all that a cactus is the type of plant that fits best, but it needs to be safely tied down to its place in case of hard weather
.* *And who wants to have a cactus on board! So, it is easier to have a vase (or tea pot or a cut off plastic bottle) with flowers once in a while. *