What to plant in September (UK)
September is the most underrated month in the UK gardening calendar. The soil is at its warmest of the whole year — warmer than May — the autumn rain does your watering, and seeds germinate in days rather than weeks. Here's what to sow and plant while that window is open.
Veg to plant in September
🧅 Onion sets & shallots
Autumn-planting varieties like 'Radar', 'Electric' and 'Senshyu' go in from mid-September. They root before winter, sit tight through the cold, and bulb up weeks ahead of anything planted in spring. Push each set into well-drained soil so just the tip shows, 10cm apart.
🥬 Winter salads
Lamb's lettuce, mizuna, rocket, land cress and winter-hardy lettuces like 'Winter Density' and 'Arctic King' all germinate fast in September's warm soil. Sown now, they'll give you pickings right through winter — especially with a cloche or a layer of fleece over them.
🌿 Spinach
A September sowing of a hardy variety like 'Medania' produces leaves in autumn, pauses over the coldest weeks, then explodes back into growth in early spring — long before spring-sown spinach even germinates.
🌸 Spring cabbage
Plant out young spring cabbage plants now, 30cm apart, firmed in well. They stand through winter and produce sweet spring greens in April — right in the "hungry gap" when the veg patch is otherwise empty. Net them, or the pigeons will find them first.
🥕 Quick catch crops
There's still time for fast growers before the frosts: radishes (3–4 weeks), baby turnips like 'Milan Purple Top', and salad onions sown now for an early spring harvest.
Flowers to plant in September
- Daffodils and crocuses — September is the ideal month; they root strongly in warm soil. (Hold tulips back until November — here's why.)
- Hardy annuals — cornflowers, calendula, ammi and poppies sown directly now make sturdier plants that flower weeks earlier next summer.
- Wallflowers — plant out now while the soil is warm for a wall of scent next spring.
And two jobs worth doing
- Sow green manure (phacelia, field beans) on any bed that's finished for the year — it protects the soil and feeds it when dug in come spring.
- Take cuttings of tender favourites like pelargoniums and fuchsias before the first frost — free plants for next year.
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