UK flower planting runs from January to December, with the busiest sowing months between March and May. Hardy annuals like sweet peas and cornflowers sow outdoors from March when soil reaches 7-10C. Half-hardy annuals including cosmos and zinnias start indoors in April and go outdoors after the last frost in late May. Bulbs split into two windows: spring-flowering types plant October to November, summer-flowering types plant March to May.
Key takeaways
- March to May is peak flower sowing season, with over 40 species to start
- Hardy annuals sow directly outdoors from March; half-hardy annuals start indoors from April
- Last frost dates span a 4-6 week window: late April in the south to late May in Scotland
- Spring-flowering bulbs plant in October-November; summer-flowering bulbs plant in March-May
- Biennials like foxgloves and wallflowers sow in June-July for flowers the following year
- Deadheading and successional sowing extend flowering from April through to first frost in October
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Our team produces practical UK gardening guidance from source research, contributor records and established horticultural practice. Editorial standards are overseen by Matt W.
