What is "citrumelo"

n. A citrus fruit that is a cross between trifoliate orange ((taxlink Poncirus trifoliata species noshow=1)) and grapefruit

Citrumelo or Citromelo (X Citroncirus spp.) is also called Swingle citrumelo trifoliate hybrid, because it is a cold hardy citrus hybrid between a 'Duncan' grapefruit and a trifoliate orange (Poncirus trifoliata ( L.) Raf.), developed by Walter Tennyson Swingle.

Citrumelo is widely employed as a citrus rootstock, being resistant to the severe citrus tristeza virus and to the Phytophthora foot rot as well as to blight, cold, and citrus nematode.