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.
Perennials is a term that describes what many gardeners and homeowners strive for, which is a plant that comes back every spring. There are perennial plants that can meet just about every need a landscape has. Perennials range from low growing plants to tall growing plants, from those that produce colorful flowers to those that provide visual pleasure with glowing seed heads, such as those exhibited by some ornamental grasses.