September marks the gentle transition from summer into autumn, bringing cooler temperatures and a shift in garden rhythms. For UK gardeners, it is a fantastic month to plant a variety of flowers that will bring rich autumnal colours, as well as early spring blooms next year. Whether you have a large country garden, a small urban plot or containers on a balcony, knowing what to plant in September helps ensure your garden stays vibrant well beyond summer’s end.
Planting Autumn-Flowering Bulbs and Perennials
September is the perfect time to plant autumn-flowering bulbs such as colchicum, nerines and autumn crocus. These striking bulbs thrive in well-drained soil and sunny or partially shaded spots. They offer unexpected bursts of colour from late September through to November, brightening the garden as other flowers begin to fade.
Perennials like asters, sedums and heleniums can also be planted now. These plants produce lovely late-season flowers that attract bees and butterflies, supporting garden wildlife before winter. September planting gives them time to establish roots before the colder months arrive.
Sowing Hardy Annuals and Biennials
Hardy annuals such as calendula and cornflowers can still be sown outdoors in September for autumn blooms. These quick-growing flowers add cheerful colour and help fill gaps in borders.
Biennials like wallflowers and sweet williams can be sown this month to develop over winter and flower next spring and summer. These plants are great for providing long-term interest and structure in your garden.
Planting Spring-Flowering Bulbs
September is the prime time to plant spring-flowering bulbs including daffodils, tulips, crocuses and hyacinths. Planting bulbs in well-prepared, well-drained soil during this month ensures they establish strong roots and produce vibrant blooms next spring.
Consider naturalising bulbs in lawns, under trees or in wildflower meadows for a more naturalistic, wildlife-friendly display. Bulbs also attract early pollinators such as bees emerging from hibernation.
Refreshing Containers and Borders
This is a good time to refresh container plantings with hardy autumn-flowering plants such as pansies, violas and chrysanthemums. Combining these with evergreen foliage plants like ivy or box adds texture and year-round interest.
In borders, remove spent summer plants and prepare the soil by adding organic matter. Planting new perennials and bulbs now ensures a succession of flowers through autumn and into spring.
Soil Preparation and Care
Preparing soil in September is key to successful planting. Clear away weeds and debris and enrich soil with garden compost or well-rotted manure. This improves soil structure and fertility, helping new plants to thrive.
Mulching newly planted areas retains moisture and suppresses weeds. Organic mulches also support soil health as they break down.
Tips for Small Gardens and Urban Spaces
For gardeners with limited space, September is a great time to plant bulbs in pots and window boxes. Use good-quality, peat-free compost and ensure containers have drainage holes to prevent waterlogging.
Small autumn-flowering plants such as pansies and violas are ideal for adding colour to containers or small borders. Vertical gardening with climbers like clematis or ivy continues to add interest in compact spaces.
Sustainability and Wildlife Benefits
Planting autumn-flowering species supports late-season pollinators and garden wildlife. Flowers like asters and sedums provide important nectar sources during a time when food is scarce.
Choosing native plants and peat-free composts helps protect the environment. Avoiding chemical pesticides and using organic fertilisers fosters a healthy garden ecosystem.
In Summary
September is a month of opportunity for UK gardeners. From planting spring bulbs and autumn-flowering perennials to sowing hardy annuals, your efforts now will ensure a garden full of colour, texture and wildlife interest through autumn and next spring. With careful preparation and planting, your garden will continue to thrive as the seasons change.
