There is so much colour and structure to be gained from Summer flowering shrubs.
Many are easy to grow and low maintenance, providing colour for not too much hard work. As with all shrubs, they have individual growing requirements, but one general point to check is the eventual size of the shrub. The plant label should have this information. It's important the shrub does not to swamp other plants in the border.
For example, illustrated right is hydrangea lovely, but most varieties grow quite large, a spread of 1.5m, so it will take up a fair amount of the border. Similar Buddleja is great for attracting butterflies and pollinators but does mature into a large shrub.
Below are illustrations and links to information about some of the best summer flowering shrubs with lots of colourful flowers and easy to grow. The link is to the individual shrubs where there is information about their preferred growing conditions, eventual size and a growing guide for that shrub.