What Seeds to Plant in September
September is a pivotal month for gardeners, offering a final chance to sow many seeds for autumn and winter harvests, while also laying the groundwork for vibrant spring displays. Focusing on seeds suited for cooler weather and shorter days ensures success. For those in milder climates, direct sowing can continue for certain crops, whereas in colder regions, starting seeds indoors or planting hardy varieties directly into the ground becomes the priority.
- Sow hardy greens and root vegetables for autumn/winter.
- Plant spring-flowering bulbs for future colour.
- Choose cover crops for soil improvement.
- Consider perennial seeds for established gardens.
- Protect newly sown seeds from early frosts.
The key is to select species that can either mature quickly before the cold truly sets in or those that are naturally suited to overwintering, providing an early start come spring. This approach maximises garden productivity and ensures continuous interest throughout the year, transforming your outdoor space.
September's planting strategy often involves a mix of edible crops and ornamental plants. Many types of lettuce, spinach, rocket, and radishes can still be sown, provided they are quick-maturing varieties. Hardy root vegetables like carrots, beetroot, and turnips can also be direct sown, giving them enough time to establish before the soil becomes too cold for germination. For a more immediate return, consider planting young plants or plugs of brassicas that have been grown on from earlier sowings.
Hardy Vegetables for Autumn Sowing
The cooler temperatures of September are ideal for many brassicas, including kale, Brussels sprouts, and winter cabbage, especially if started from young plants. Direct sowing of spinach, mustard greens, and corn salad (lamb's lettuce) is also highly recommended. These crops are relatively frost-tolerant and will provide fresh greens well into the late autumn or even winter months in sheltered locations. Don't overlook the potential of broad beans and certain varieties of peas; sown in early September, they can establish a strong root system to survive the winter and provide an exceptionally early crop the following spring.
Flowers and Bulbs for Seasonal Interest
For ornamental gardens, September is a prime time for planting spring-flowering bulbs like tulips, daffodils, hyacinths, and crocuses. Getting these into the ground now allows them sufficient time to root before winter arrives, ensuring a spectacular display of colour as the weather warms. Many hardy annuals, such as calendula, poppies, and cornflowers, can also be sown directly into the ground in September. They will germinate and grow into sturdy young plants that can overwinter, flowering much earlier and more profusely the following year than those sown in spring. Consider planting biennials like wallflowers and sweet williams, which will establish now and flower next spring.
Autumn Vegetables for September Planting
As summer plants fade, September offers a specific window for sowing vegetables that thrive in cooler conditions or require a long period to mature before winter. The choice of vegetables often depends on your climate zone; milder regions can continue with a wider range of sowings than those experiencing early frosts.
For direct sowing, consider fast-growing leafy greens. Varieties of spinach, mizuna, and oriental mustards are excellent choices; they can often be harvested within 4-6 weeks. Lettuce varieties bred for cooler weather, such as romaine or butterhead types, can also be sown now, provided they are protected from the harshest early autumn chills. Radishes are another excellent option for quick harvests, with some varieties maturing in as little as 25 days. Planting them in succession every two weeks can yield a continuous supply.
Root vegetables benefit from being sown in September. Carrots, particularly shorter, faster-maturing varieties, can still be sown, as can beetroot and turnips. These will develop into usable sizes before the ground freezes. Swede and parsnips, which require a long growing season, are best planted as young seedlings if not already sown, but seeds can still be sown in early September in warmer climates for overwintering.
Brassicas and Legumes
Many brassicas, including kale, broccoli, and savoy cabbage, are often planted as young plants or seedlings in September for a late autumn or winter harvest. If you are sowing seeds, choose varieties that are known for their cold hardiness and maturity time. Spring cabbage varieties, sown now, will establish a strong root system and be ready for overwintering, providing an early spring harvest.
For legumes, broad beans are a traditional choice for autumn sowing in many parts of the UK. Sowing them in early to mid-September allows them to develop a robust root system, making them more resilient to winter conditions and providing a much earlier crop than spring-sown plants. Similarly, certain types of peas can be sown now for an early spring harvest, provided they are given some protection.
What Flowers and Bulbs to Plant in September
September is a crucial month for planning and planting for the following year's floral displays. While many summer flowers have finished their show, now is the time to introduce bulbs that will provide early spring colour and sow seeds that will establish for later blooms.
Spring-flowering bulbs are the stars of September planting. Tulips, daffodils, hyacinths, crocuses, and alliums should be planted generously. Aim to get them into the ground before the soil becomes waterlogged or too cold to work. The depth and spacing depend on the bulb type, but a general rule is to plant them at a depth of about two to three times their height. Planting in drifts or groups often yields a more impactful visual result than scattering them individually.
Beyond bulbs, September is an excellent time to sow hardy annuals directly into the ground. These are plants that complete their life cycle within one year but can be sown in autumn to overwinter as small plants, giving them a significant head start. Examples include calendula, poppies (especially oriental poppies), cornflowers, nigella, and larkspur. They will germinate in the cooler soil and develop strong root systems, ready to burst into flower much earlier and more vigorously in the spring than spring-sown counterparts.
Cover Crops and Green Manures
While not strictly for ornamental or direct food consumption, planting cover crops in September is a vital gardening practice. These plants, such as phacelia, vetch, or rye, are sown to protect and improve the soil over winter. They prevent soil erosion, suppress weeds, and when dug back into the soil in spring, they add valuable organic matter and nutrients. This 'green manure' benefits the soil structure and fertility for future planting seasons, a cornerstone of sustainable gardening.
Perennial seeds can also be sown in September. While many perennials are best propagated from cuttings or divisions, sowing seeds now allows them to establish over autumn and winter, ready for planting out in their final positions in spring. This is particularly useful for slower-growing perennials or those you wish to propagate in larger numbers.
Preparing Your Garden for September Sowing
Successful seed planting in September relies heavily on good soil preparation and understanding your local climate's nuances. The cooler weather can affect germination rates and the establishment of young plants, so giving them the best possible start is paramount.
Begin by clearing any spent summer crops. Remove dead or diseased plant material to prevent issues from carrying over into the next season. Weeding is also essential; removing existing weeds before sowing reduces competition for your new seeds. Fork over the soil to a depth of about 20-25 cm, breaking up any compacted areas and improving drainage. Incorporate well-rotted compost or other organic matter to enrich the soil and improve its texture, which is vital for healthy root development.
When sowing seeds directly into the ground, ensure the soil is moist but not waterlogged. Create a fine tilth on the soil surface by raking it smooth before sowing. Follow the seed packet instructions carefully for depth and spacing, as these vary significantly between plant types. For smaller seeds, a light scattering is often best, followed by a gentle covering of soil or compost.
Protecting Young Plants and Seeds
Early autumn frosts can be a concern for newly sown seeds and young plants. Consider using fleece or cloches to provide a protective layer, especially for more tender varieties. This barrier will trap warmth and shield them from the cold, encouraging growth and preventing damage. For bulbs, ensure they are planted at the correct depth; this provides insulation against extreme temperatures and helps them establish before the ground hardens with frost.
In regions prone to heavy rain, raised beds or containers can be invaluable. They offer better drainage, preventing seeds from becoming waterlogged and rotting, and allow you to control the soil conditions more precisely. Choosing the right location for your September sowings is also critical. Most vegetables and many flowers will benefit from a position that receives ample sunlight, even as the days shorten.
Alternatives for Continued Autumn Harvests
For gardeners keen to extend their harvest well into autumn and even winter, September sowing is not the only option. While direct sowing of certain seeds remains viable, alternative methods and plant choices can ensure a continuous supply of fresh produce.
Consider planting out young plants or plugs that have been raised earlier in the season. Many brassicas, such as winter cabbages, kale, and Brussels sprouts, are more reliably established when transplanted in September rather than direct sown. This gives them a head start and ensures they have enough time to mature before the harshest winter weather sets in. Similarly, leeks and onions can often be planted out as young plants to overwinter and provide an early harvest next year.
If direct sowing has been missed for some crops, or if you're looking for faster results, explore varieties specifically bred for quick growth or overwintering. For instance, some spinach varieties are very cold-hardy and can produce a decent crop even after a light frost. Quick-growing salad leaves, such as rocket and mustard greens, can provide successive harvests if sown in batches, even in cooler conditions.
Year-Round Gardening with Protected Cropping
For those with access to cold frames, polytunnels, or greenhouses, September opens up possibilities for sowing or planting crops that would otherwise be too late in the season. These protected environments allow you to extend the growing season significantly, enabling you to sow seeds like more lettuce varieties, spinach, and even certain herbs that might struggle outdoors. They also provide a crucial sanctuary for more tender plants or those started from seed.
Furthermore, if your focus is on extending the harvest of existing crops, consider succession planting earlier in the season. For example, sowing radishes or lettuce every two weeks through late summer means you will have a staggered harvest that continues into early autumn. Similarly, planting out garlic cloves in late autumn (though technically October/November for many) can be seen as a progression from September planning.