German Grapefruit

Last weekend I was on a short trip to Bielefeld. While there I had a homegrown grapefruit, picked off the bush that morning. The bush was about 18years old and had been bought as a lemon tree. After nearly dying in the first couple of years it thrived, being out on a balcony in summer and a cool shady stairwell in winter. Been repotted every few years. It apparently produced it's first fruit a couple of years ago. These were small. This year, when I saw it, it had 6-10 fruit in different stages of ripeness. The one I had was about 10cm in diameter, had quite a thick skin, but was tasty and definitely a grapefruit.

 

I grew one many years ago from seed and did my usual winter covering but with no heat, it survived every winter but never fruited.
Eventually I had to get rid of it due to building work.