(1 Gallon) MARS Seedless Grape Vine, Mars is a blue seedless grape, good in hot summer areas. (1 Gallon) MARS Seedless Grape Vine, Mars is a blue seedless grape, good in hot summer areas. Medium to large, sweet, juicy, seedless, crimson fruit turns deep blue when fully ripe. Full Sun, Self Pollinating, Ripens early. Plants are fairly vigorous and are very productive. Thick Skin. Hardy in zones 5-8. Among the most cold hardy of the seedless grapes.