No way to stop them once they start, that I know of. For next year, you might want to double check that the variety you are planting is suitable for a spring harvest. Another thing that may help is to put more slow-acting nitrogen in the soil before planting, so that the rosettes get larger before frost, and more nitrogen is released in the early spring, when the heads should be expanding. Another thing that may help is to mulch the soil surface before frost, to even out soil temperatures in spring.

thanks for your advice will try it this year the verity,s i,ve tried are flower of spring and apiral thanks