Citrumelo (xCitroncirus) is a cross between a grapefruit and the very hardy trifoliate orange (Poncirus trifoliata) and tastes like something between the two. It is hardy outdoors on the west coast.

xCitroncirus forms large grapefruit-sized fruits that are yellow to light orange with thin skin and a flavour like a cross between a lemon and a grapefruit.

'Dunstan' citrumelo forms large grapefruit-sized fruits. It is easily hardy to zone 8 and most likely zone 7!