Eryngium (Sea Holly) in Zone 3a & 3b
Eryngium planum
Yes, eryngium (sea holly) grows in zones 3a and 3b. Start seeds indoors Feb 28–Mar 7 and plant out Jun 6–Jun 13.
When to plant eryngium (sea holly) in zone 3b
Zones 3a and 3b share the same average frost dates, so this page covers both.
Method: Start indoors: Start indoors from seed, then transplant outside. It needs a head start most zones can't give it by direct-sowing alone.
| Start indoors | Feb 28–Mar 7 |
|---|---|
| Direct sow / transplant outside | Jun 6–Jun 13 |
| Estimated bloom | About a year after planting |
Spacing: 1 per square foot (square-foot-gardening spacing). Mature height: 2-3 ft.
Plant alongside it in zone 3b
These go outside within two weeks of eryngium (sea holly) in zone 3b, so one planting day can cover them.
- NasturtiumJun 6–Jun 13
- MarigoldJun 6–Jun 13
- Ageratum (Flossflower)Jun 6–Jun 13
- Annual Geranium (Pelargonium)Jun 6–Jun 13
- Butterfly Weed (Asclepias)Jun 6–Jun 13
- Campanula (Bellflower)Jun 6–Jun 13
Eryngium, commonly called sea holly, looks like a thistle crossed with a metal ornament, its spiny bracts taking on a blue or silvery sheen that holds up well both fresh and dried.
How eryngium (sea holly) fits zone 3's season
Zone 3b's frost-free window runs about 98 days, from May 30 to September 5. Eryngium (sea holly) takes about a year from planting to first bloom, so it spans more than one growing season.
Eryngium (Sea Holly) planting windows in every zone
Zone 3b is highlighted. Useful for comparing against a neighbouring zone, or for a garden somewhere else.
| Zone | Start indoors | Sow or plant out | Bloom |
|---|---|---|---|
| 3a & 3b (your zone) | Feb 28–Mar 7 | Jun 6–Jun 13 | About a year after planting |
| 4a & 4b | Feb 13–Feb 20 | May 22–May 29 | About a year after planting |
| 5a & 5b | Feb 8–Feb 15 | May 17–May 24 | About a year after planting |
| 6a & 6b | Jan 24–Jan 31 | May 2–May 9 | About a year after planting |
| 7a & 7b | Jan 9–Jan 16 | Apr 17–Apr 24 | About a year after planting |
| 8a & 8b | Dec 24–Dec 31 | Apr 1–Apr 8 | About a year after planting |
Good companions
No well-established companions for eryngium (sea holly).
Where to buy eryngium seeds
None of the seed suppliers we list carries eryngium seeds right now. A local garden center or a specialty seed house is the place to look.
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing eryngium (sea holly)" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 3b calendar · Plan your beds in the Garden Designer →
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Growing Eryngium (Sea Holly) in USDA zone 3b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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