Waltham is a popular variety of open pollinated green calabrese, producing a good sized head for Autumn cropping.
Sow in a seedbed outdoors in April. Transplant into their permanent positions as soon as the plants are large enough and there is space in the garden. Do not let the seedlings get overcrowded or they will soon become leggy and will not make such good plants. If your seedlings do get leggy, it is possible to plant them rather deeper into the soil - the buried stems will soon form roots and the plant will be better supported.