A number that is calculated to summarise a group of numbers. The most commonly used average is the mean, the sum of the numbers divided by however many numbers there are in the group. The median is the middle value in a group of numbers ranked in order of size.
Perennials: cutting back. Perennials are not demanding plants, but trimming them after flowering finishes in autumn helps improve their appearance and flowering. However, you can leave some stems over winter to provide homes and food for wildlife, and then trim back in spring.utting back herbaceous perennials during autumn restores order and tidiness to the garden. However, this removes potential winter interest, in the form of height and structure, plus food and habitat sources for wildlife.
Contact Us. Perennials This time the Latin 'perennis' means 'many years'. Sometimes called 'herbaceous perennials', which simply means they 'disappear' in winter. In fact, they die back to a rootstock where next year's shoots are protected and then magically grow back each spring.ut 'bedding' is usually taken to mean those half-hardy annuals or half-hardy perennials planted out to make a splash of colour in the summer. For example; petunias, begonias, pelargoniums and calceolarias. Find out more about taking delphinium cuttings and growing chrysanthemums and fuchsias on the main site.