Summer
Although I always think of may as the late spring many people look at the warm days as a summer indication. Don’t be fooled the daylight hours are not quite there yet and the evenings do get a little chilly, so if you put out some summer bedding plants they could struggle to get going, leave planting until the third week in May to be safe.
As late May approaches you will see a surge in growth of your perennials, especially the early summer ones, if your looking to buy for your borders remember that late flowering perennials are usually available from about mid June onwards, although they will flower next year is when you will see them at there best.