beetroot food green red summer vegetable garden leaves allotment Beta bulbous garden globe plant purple root round vegetable beet beetroot dye beta vulgaris betacyanins betaine betanin carotenoid color coloring colour colouring crimson cultivar cut firm flavour garden beet halved halves healthy nutritious radiating raw red beet red food colourant reddish rings root vegetable stain staining table beet uncooked apple carotte citrus potato potatoes swede union