September.
Your spring-flowering bulbs should be planted this month. In some cases it cannot be done, because their places are not vacant yet, or because you mean to dig over your whole garden later in the autumn. But where complete reorganization is unnecessary, try to find room for your bulbs as soon as possible.
If you have any biennial or perennial plants grown from seed sown in May, they should now be strong and big enough to transplant to their flowering quarters. This is an operation you can carry out either in autumn or spring, but not in winter. Frost soon kills plants that have not had time to take a firm hold of the soil.
Autumn brings much labour in the garden in the shape of tidying, weeding, and preparing for next year. Annuals that have become shabby may be pulled up and thrown away. They will leave a bare place that you must dig over well. Before you replant it you must consider whether what you are going to plant would like a little manure beneath its roots, or as a blanket on the top. A greedy annual has probably impoverished the soil.
Herbaceous plants that flower in spring may all be divided and reset now.