Safflower (Carthamus tinctorius)
3 sources cited · Verified
The short answer
- Plant
- Mid April to late April
- 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 April to late April.
Safflowers (Carthamus tinctorius) — Annual (RHS.
Timing is the decision that matters most in Canada: there are 6 separate regional sowing windows, ranging from early March in Pacific Coastal Mild to late May in Far North & Alpine.
Core growing advice on this page is checked against named horticultural sources — see References.
Regional Planting Calendar
| Region | Sow |
|---|---|
| Central Continental derived | mid April to late April |
| Prairies & Short-Season Continental derived | early May to late May |
| Pacific Coastal Mild derived | early March to mid March |
| Far North & Alpine derived | late May to early June |
| Atlantic Maritime derived | late April to early May |
| Inland Valleys & Southern Lakes derived | mid April to late April |
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.
Central Continental - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette stage tolerates light frost, so safflower can be direct-seeded shortly before the last frost, needing at least 120 frost-free days and 2200 growing degree days to mature. Applied to a mean last frost of 30 April (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 16 April to 30 April. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Prairies & Short-Season Continental - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette stage tolerates light frost, so safflower can be direct-seeded shortly before the last frost, needing at least 120 frost-free days and 2200 growing degree days to mature. Applied to a mean last frost of 21 May (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 7 May to 21 May. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Pacific Coastal Mild - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette stage tolerates light frost, so safflower can be direct-seeded shortly before the last frost, needing at least 120 frost-free days and 2200 growing degree days to mature. Applied to a mean last frost of 18 March (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 4 March to 18 March. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Far North & Alpine - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette stage tolerates light frost, so safflower can be direct-seeded shortly before the last frost, needing at least 120 frost-free days and 2200 growing degree days to mature. Applied to a mean last frost of 5 June (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 22 May to 5 June. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Atlantic Maritime - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette stage tolerates light frost, so safflower can be direct-seeded shortly before the last frost, needing at least 120 frost-free days and 2200 growing degree days to mature. Applied to a mean last frost of 7 May (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 23 April to 7 May. Your own local frost date is what matters — a region spans a range, and this figure comes from one representative station within it.
Inland Valleys & Southern Lakes - detail & sources
DERIVED from this region's own frost normal, not quoted for the region. Rosette stage tolerates light frost, so safflower can be direct-seeded shortly before the last frost, needing at least 120 frost-free days and 2200 growing degree days to mature. Applied to a mean last frost of 30 April (NOAA NCEI 1991-2020 for the USA; Environment and Climate Change Canada normals for Canada), that gives 16 April to 30 April. 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 Canada?
In Pacific Coastal Mild, from early March. In Far North & Alpine, wait until late May. 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 early March to early June.
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
Short-season growing is arithmetic before it is technique: days to maturity against frost-free days decides what will finish at all. The Canada Garden Planner does that subtraction for your region before you sow.
Get the Canada Garden Planner →Instant PDF download · Written for Canadian growing conditions
Vegetable Growing Guides Canada
Last verified 2026-09-03
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.