Sea holly

E. bourgatii, from Spain and the Pyrenees, has three first-rate cultivars, one of the best being 'Picos Blue'. It's very similar to the parent but is slightly bluer, larger and more robust, with the same beautiful spiny rosette of grey-green leaves with prominent white veins and pale green flowers. Good alternatives are 'Oxford Blue', which has been given the Award of Garden Merit (AGM) by the Royal Horticultural Society, and 'Picos Amethyst'. Like E. alpinum, It is wonderfully tactile and is best planted to the front of a border. Provide poor, free-draining soil, and ideally a position at the foot of a wall where the soil doesn't stay soaking wet over winter.