We don't know of any larger red onion varieties than Mammoth Red, and it's certainly a favourite with those who like to exhibit their produce at shows. It's not just grown for the size of the onions though, as it also has a lovely sweet flavour, is versatile in the kitchen, and stores well after the harvest period of late summer and early autumn. Definitely one to try!
Plant out when the danger of frost has passed, 30-40cm apart with a similar distance between rows.
