🌍 Built for UK, USA, Canada & Worldwide Gardens Free Growing Guides for Every Region Love It or Your Money Back Secure Checkout Instant PDF Download Checked Against RHS, USDA & Agri-Food Canada Data Free Garden Layout Planner
🌍 Built for UK, USA, Canada & Worldwide Gardens Free Growing Guides for Every Region Love It or Your Money Back Secure Checkout Instant PDF Download Checked Against RHS, USDA & Agri-Food Canada Data Free Garden Layout Planner
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.
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
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
This page gives you the thresholds; the planner turns them into your own calendar. It works from what you can observe and measure in your garden rather than from dates written for somebody else’s latitude.
Science-based growing guides · Thresholds that hold in any climate
This guide states the conditions the plant itself responds to — soil temperature, frost tolerance, day length — rather than dates, because the same calendar month means opposite seasons in the northern and southern hemispheres. Anything genuinely restricted to one part of the world is named as such rather than presented as universal. Written and maintained by our editorial team against international horticultural research and extension sources.
Sketch your exact plot shape, pick your crops, and get a spacing-accurate bed layout with companion pairings and a rotation plan. Spacing, companion pairings and rotation are the same in every climate and both hemispheres — pair the layout it gives you with when to plant to set your own timing from soil temperature.
