Allium

With a wide variety of species (including onion and garlic), the ornamental forms that flower in May herald summer is round the corner. The large spherical heads of tiny flowers come in many shades of purple and some whites, at a variety of heights. Some impressive cultivars include the 80cm Allium ‘Globemaster’ with a deep violet flower head to the lower-growing Allium christophii, which has star-like, rosy violet flowers. Easy to plant in autumn as bulbs, they also bulk up quickly, so you can divide and spread throughout the whole garden. They make wonderful cut flowers and great seed heads during summer too.