Growing Carthamus (Safflower): A Complete Profile
By Growing Home Greens Team · August 10, 2026
Carthamus, better known as safflower, is a thistle-like cut flower historically grown as an oilseed and dye crop, with bright orange-yellow blooms that hold their color well once dried.
Sowing
Direct-seeding is recommended, done after the last frost with the seed covered lightly; seedlings develop best at 65°F after germination. Transplanting also works, started 4 to 5 weeks before planting out. Germination takes 10 to 14 days at 68-72°F. Space plants 6 to 9 inches apart.
Cut at the right moment
Fresh-cut harvest timing matters more than usual here: cut stems once flowers have begun to open and show color, since stems cut before any color shows won’t continue opening once in a vase, unlike a lot of cut flowers that finish opening after cutting. For dried arrangements, wait until flowers are fully open before air drying.
Heat tolerance has limits
Despite its thistle-like, tough appearance, safflower handles intense heat less well than expected. Southern growers should provide roughly 30 percent shade or some afternoon shade to keep plants performing well through summer.
Carthamus has no well-established companion pairings, and nothing it needs to be kept away from. At 4 plants per square foot, it’s a good addition to a dried-flower row in the Garden Designer, with afternoon shade planned in for hot-summer regions.
Source: Carthamus (Safflower): Key Growing Information, Johnny’s Selected Seeds.
Companion planting guide for Carthamus (Safflower) · Find your planting dates
Typically viable in USDA zones 2-11. Not sure your zone? Look it up by ZIP code.
Mature height: 1.5-2 ft
Method: Either: Start indoors for an earlier harvest, or direct-sow outside for less fuss. Either works.
When to plant carthamus (safflower), by zone
Every zone carthamus (safflower) grows in. Pick your zone in the header and it will be highlighted here. Each zone links to its full page.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 2a & 2b | Apr 22–Apr 29 | May 20–May 27 | Aug 18–Aug 25 |
| 3a & 3b | May 2–May 9 | May 30–Jun 6 | Aug 28–Sep 4 |
| 4a & 4b | Apr 17–Apr 24 | May 15–May 22 | Aug 13–Aug 20 |
| 5a & 5b | Apr 12–Apr 19 | May 10–May 17 | Aug 8–Aug 15 |
| 6a & 6b | Mar 28–Apr 4 | Apr 25–May 2 | Jul 24–Jul 31 |
| 7a & 7b | Mar 13–Mar 20 | Apr 10–Apr 17 | Jul 9–Jul 16 |
| 8a & 8b | Feb 25–Mar 4 | Mar 25–Apr 1 | Jun 23–Jun 30 |
| 9a & 9b | Jan 18–Jan 25 | Feb 15–Feb 22 | May 16–May 23 |
| 10a & 10b | Jan 2–Jan 9 | Jan 30–Feb 6 | Apr 30–May 7 |
| 11a & 11b | Dec 4–Dec 11 | Jan 1–Jan 8 | Apr 1–Apr 8 |
Bloom dates are about 90 days after the sow or plant-out date, not after starting seeds indoors.
Zone 2 sows before zone 3 here, which looks wrong and is not. USDA zones rank winter cold, not season length, and zone 2 is mostly interior Alaska, where hard winters come with warm summers. More on what a zone measures.
See exact start-indoors, direct-sow, and harvest dates for your zone →
How many Carthamus (Safflower) plants fit per square foot?
Spacing: 4 per square foot (square-foot-gardening spacing). Mature height: 1.5-2 ft.
Varieties worth considering
- 'Zanzibar' carthamus: Johnny's Selected Seeds describes this as a sturdy, versatile option for both flowers and foliage, one of their standard carthamus offerings for cut-flower growing. (source)
Why each variety is listed comes from the source shown next to it. We haven't grown these ourselves yet, so treat this as a research-backed starting point, not a personal endorsement. The buy links are separate from those sources: they go to seed suppliers that sell that exact variety, and we may earn a commission on some of them.
Where to buy carthamus seeds
None of the seed suppliers we list carries carthamus seeds right now. A local garden center or a specialty seed house is the place to look.
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See it growing
Search YouTube for "growing carthamus (safflower)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
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Growing Carthamus (Safflower): A thistle-like cut flower historically grown as an oilseed and dye crop, whose bright orange-yellow blooms hold their color well dried.
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