Safflower (Carthamus tinctorius)
3 sources cited · Verified
The short answer
- Plant
- Mid February to early March
- Site
- 6+ hours of sun, soil pH 6–7.5
- Biggest risk
- Alternaria leaf spot of safflower
In the UK, safflowers go in the ground mid February to early March.
Safflowers (Carthamus tinctorius) — Annual (RHS.
Timing is the decision that matters most in the USA: there are 7 separate regional sowing windows, ranging from mid January in Deep South & Gulf Coast to mid April in Intermountain West.
Core growing advice on this page is checked against named horticultural sources — see References.
Regional Planting Calendar
| Region | Sow |
|---|---|
| Pacific Northwest derived | mid February to early March |
| Northeast & New England derived | mid March to early April |
| Lower Midwest & Ohio Valley derived | late March to mid April |
| Intermountain West derived | mid April to early May |
| N. Plains & Upper Midwest derived | early April to late April |
| Mid-Atlantic & Upper South derived | mid March to early April |
| Deep South & Gulf Coast derived | mid January to early February |
Rows marked derived are interpolated between regions our sources do state, because no source we consulted gives a figure for that region specifically. They are deliberately wider to reflect that uncertainty.
Pacific Northwest - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 8 March (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 15 February to 8 March. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Northeast & New England - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 6 April (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 16 March to 6 April. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Lower Midwest & Ohio Valley - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 16 April (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 26 March to 16 April. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Intermountain West - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 6 May (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 15 April to 6 May. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
N. Plains & Upper Midwest - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 25 April (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 4 April to 25 April. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Mid-Atlantic & Upper South - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 4 April (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 14 March to 4 April. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Deep South & Gulf Coast - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette tolerates temperatures as low as 20F, so safflower is direct-seeded before the last frost -- around late April to early May in the Upper Midwest, with a planting-depth of 1-1.5in; risk increases if planted after mid-May. Applied to a mean last frost of 2 February (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 12 January to 2 February. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Quick Facts
At a Glance
Soil & Growing Conditions
Growth Stages
Harvest & Storage
When to pick: Ready to harvest when most of the leaves turn brown and the seeds are white and hand-thresh easily; typically early to late September in the northern US (Wisconsin Extension). Takes 110-140 days from planting to maturity (Wisconsin Extension; NDSU).
Diseases
Pests
Safflower Photo Gallery
References
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In North Dakota, safflower normally requires 110-120 days from emergence to maturity. Grows best on deep, fertile, well-drained loam soils with good water-holding capacity; soil pH of 6.0 appears adequate. Planting depths of 1-1.5in are optimum, do not seed deeper than 2in. Taproot can penetrate 8-10ft in deep soils.
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Erect branching annual to 60cm, spiny leaves, thistle-like orange/yellow flower-heads with prominent green bracts. Propagate by seed sown in gentle heat, early to late spring. Grow in any light, well-drained soil in full sun; tolerates acid/alkaline/neutral pH. Hardiness H5 (-15 to -10C). Height 0.5-1m, spread 0.1-0.5m. Generally pest-free and disease-free (garden-scale UK growing). Native to Western Asia. Family Asteraceae.
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Deep, fertile, well-drained soil with high water-holding capacity; soil pH of 6.0 adequate; high soil salinity reduces germination. Planting depth 1-1.5in. Seeding rate 20-25 lb/acre dryland, 25-35 lb/acre irrigated. Row spacing 6-7in, ~6 plants/sq ft. Plant late April to early May in the Upper Midwest; risk if planted after mid-May. Days to maturity 110-140. Tolerates temperatures as low as 20F at the rosette stage, but is very frost-sensitive after stem elongation. Needs a minimum 120 frost-free days and 2200 growing degree days; not recommended above 15in annual precipitation; prefers warm, sunny, dry conditions during flowering and seed-fill. Diseases: Alternaria leaf spot (Alternaria carthami) causing large, brown, irregular leaf spots; bacterial blight (Pseudomonas syringae) with yellow-green margined lesions; Sclerotinia and Botrytis flower-head rots; various root rots and wilts. Pests: wireworms, cutworms and seed corn maggots damage seeds/seedlings; thrips, lygus bugs, grasshoppers and sunflower moths damage later growth -- sunflower moth can cause 20-30% loss if damage occurs early in flowering. Harvest when most leaves turn brown and seeds are white and hand-thresh easily; early to late September in the Upper Midwest.
3 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 safflowers in the USA?
In Deep South & Gulf Coast, from mid January. In Intermountain West, wait until mid April. 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 safflowers?
Sow mid January to early May.
What soil pH do safflowers 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 safflowers?
Our data links 2 diseases and 6 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.
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Last verified 2026-09-03
Where To Go From Here
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