Thank you for your lovely message. Wish I could tell you more about the grapefruit tree but I am still fairly new to all this. I am assuming that because it is in a small courtyard with high walls all around it, the frost doesn't affect it. I've seen beautiful orange & lemon trees here in our village too, but all the time protected by high walls around them. Normally citrus fruits grow further south in Spain where the climate is hotter, so I suppose the walls fix this problem here.