If there is one plant on the allotment that almost impossible to get wrong it is Kale. These hardy stalwarts of the winter allotment provide food from summer all the way through to the hungry gap the following spring. Often kale can be quite a large plant getting upwards of a metre. If you are on a windy site or can only provide netting to a certain hight then dwarf green curled could be an option, growing to a slightly more lower 40-60cm.