Hah, I am in this same position often. Rare (for this area) plant nobody else has... no local market to sell it to, too big to ship, don't want to give it away because the container and the soil is worth something to me. End up saving the soil and trashing the plant.
I guess I could offer them to Longwood Gardens but I'm sure they have enough resources if they actually wanted these types they could easily obtain them. They don't seem interested in fruit trees, the only ones I see in their greenhouse are cattley guava and oroblanco grapefruit.