The blood orange is a mutation of a sweet orange, with a darker skin pigment and a deep crimson flesh. The trees are evergreen with a rounded and spreading shape and glossy foliage, thought to have originated in Southern Europe. They are typically smaller and sweeter than a regular orange, with pitted skin and few seeds. The red pigmentation varies with climate and can be intense when blood oranges are grown in regions with large diurnal temperature fluctuations. The pigment in blood oranges is due to the presence of anthocyanin; it is not typically found in citrus and is usually associated with other red fruit and flowers.