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How to Grow Sunflowers UK | Regional Planting Calendar
Move through the SoilCommander growing library like a course: keep the navigation in place, open the next lesson, and build your garden plan step by step.
In the UK, sunflowers go in the ground late March to late May.
Sunflowers (Helianthus annuus) — annual.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from late March in Southern England to late March in Scotland.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
RHS: sow indoors from late March, or direct outdoors mid-April to May; a single window is applied uniformly across all four sub-regions since the source gives no UK-region-specific gradient.
Midlands - detail & sources
RHS: sow indoors from late March, or direct outdoors mid-April to May; a single window is applied uniformly across all four sub-regions since the source gives no UK-region-specific gradient.
Northern England - detail & sources
RHS: sow indoors from late March, or direct outdoors mid-April to May; a single window is applied uniformly across all four sub-regions since the source gives no UK-region-specific gradient.
Scotland - detail & sources
RHS: sow indoors from late March, or direct outdoors mid-April to May; a single window is applied uniformly across all four sub-regions since the source gives no UK-region-specific gradient.
Sow indoors from late March for a head start, or direct outdoors mid-April to May, in 2cm-deep holes 30cm apart (RHS).
Establishment and staking
1
Thin to about 45cm apart, keeping the strongest plants; place a strong bamboo cane at planting time and tie the stem loosely as it grows, since most varieties need support (RHS).
Rapid growth and flowering
6
Thirsty plants needing consistently moist soil; feed with a potassium-rich fertiliser to encourage flowering; the large yellow-petalled flower head opens through summer (RHS).
Seed ripening and harvest
8
Leave the flower head standing for at least two weeks after flowering so birds can also feed, then cut before they take it all, dry for about a week, and rub over newspaper to release the seed (RHS).
When to pick: RHS: sown March-May, flowering in August (annual). NC State: blooms "from July to October"; planted "after the last frost in the spring, and harvested before the first frost in the fall"; mature seedheads indicated by "standing dead flowers" left "into the winter" as a bird-feeding indicator. RHS: for edible seed, "collect some of the seeds from your plants at the end of the season" rather than leaving all seedheads for birds.
Storage
Dry seedheads and store seeds in a cool, dry place
6 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.
Frequently Asked Questions
When should I sow sunflowers in the UK?
In Southern England, from late March. In Scotland, wait until late March. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.
When do I sow sunflowers?
Sow late March to late May.
What soil pH do sunflowers need?
A pH of about 6–7.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.
What problems affect sunflowers?
Our data links 2 diseases and 2 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.
UK vegetable growing guides · Checked against RHS & Met Office guidance
Every SoilCommander guide is written and maintained by our editorial team for real UK growing conditions, and reviewed against Royal Horticultural Society growing advice and Met Office climate data before publication.
Sketch your exact plot shape, pick your UK crops, and get a spacing-accurate bed layout with companion pairings, a rotation plan and month-by-month sowing dates — every fact sourced from RHS and Garden Organic.
