We have in our garden a lemon/grapefruit tree which we did ourselves as an experiment as we already have the lemon/orange (not seperate lemons and oranges) they look like an overgrown lemon with a grapefruit skin and taste somewhere in between, I took one to the last car boot sale after making marmalade with some, they all sold out immediately, will make more for the next one, the taste is quite different.