What to plant outdoors in September?
Plant out any biennial plants sown earlier in the year. This includes foxgloves, wallflowers and pansy plants. Plant new perennials, trees and shrubs. Now is a good time as the soil is still warm and increasing rainfall should be on its way. If you sowed any spring-flowering biennials such as pansies, honesty, foxgloves, verbascums or wallflowers, earlier in the summer, they will now need planting out. This is a good time of year to plant new perennials, especially towards the end of September, as the soil is still warm, but moisture levels are increasing.