Asters or Michaelmas daisies are perfect for late colour. They bear clusters of daisy flowers in an array of bright shades of blue,red and white in late summer and autumn. Aster enjoy most soil types as long as the soil is well-drained. As with most perennials grown for flower power they perform best in a sunny open site. They suffer with mildew in wet summers, which is another way of saying in England, but you can hide it well by planting them amongst other plants that will hide the ugly bits. It's well worth it as the display in autumn is fabulous and will go on until the frost knocks them back for the winter. They look a bit ugly when the go black, so cut them back hard and in a mild winter you will get some new leaves through quite early. The new leaves for the bulk of the growing season are particularly fresh lance shaped and perfect green. If you can be bothered in winter divide them up every 4-5 years or if they get too big. They are easy to reproduce this way and you can give friends and family some of your divided clumps.