'Blanco Duro' is most similar to 'White Sweet Spanish Ringmaster'. It is somewhat smaller, and is about 10-12 days earlier. Plants produce a large, white, globe shape bulb, with medium scales. The flesh is white, firm and moderately pungent. Overall storage quality is fair. The necks are small and cure will after top-down. If well cured and given good ventilation in storage, the bulbs will keep longer than most white onions.