If you mean Brussel sprouts, no, they're grown from seed usually every year.

thanks, its just that i have recently returned to my allotment after the winter break and found th old plants flowering and new growth at the base

Brussels sprouts flower in their second year and then die. Any new growth will not give you viable sprouts. Have to confess I am surprised you are only now visiting your allotment in May.

thank you, i am going to keep them in as they are covered with bees

Good bee food! I have heard of Kale living more than one year--"Walking Stick Kale" is amazing--but I don't know if Sprouts can do the same.

Brassicas are biennials if left alone...