Hollyhock in Zone 4a & 4b
Alcea rosea
Yes, hollyhock grows in zones 4a and 4b. Plant it outside May 1–May 8.
When to plant hollyhock in zone 4b
Zones 4a and 4b share the same average frost dates, so this page covers both.
Method: Direct sow: Direct-sow outside. It doesn't transplant well, or doesn't need the extra time indoors.
| Start indoors | Not typically started indoors |
|---|---|
| Direct sow / transplant outside | May 1–May 8 |
| Estimated bloom | Oct 28–Nov 4 (~180 days after direct-sowing) |
Spacing: about 5 square feet per plant (square-foot-gardening spacing). Mature height: 5-9 ft.
Plant alongside it in zone 4b
These go outside within two weeks of hollyhock in zone 4b, so one planting day can cover them.
- Agrostemma (Corn Cockle)May 1–May 8
- AstilbeMay 1–May 8
- Bachelor's Button (Cornflower)May 1–May 8
- Basket-of-GoldMay 1–May 8
- Bupleurum (Thoroughwax)May 1–May 8
- CalendulaMay 1–May 8
Hollyhock is a garden fixture that asks for patience and plenty of vertical space. It's a biennial in most climates, meaning it spends its first year just building a rosette of leaves and doesn't bloom until the second, and by the time it does, it can tower up to 9 feet.
How hollyhock fits zone 4's season
Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Hollyhock needs about 180 days from sowing to first bloom.
Hollyhock planting windows in every zone
Zone 4b 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 | Not usually | May 16–May 23 | Nov 12–Nov 19 |
| 4a & 4b (your zone) | Not usually | May 1–May 8 | Oct 28–Nov 4 |
| 5a & 5b | Not usually | Apr 26–May 3 | Oct 23–Oct 30 |
| 6a & 6b | Not usually | Apr 11–Apr 18 | Oct 8–Oct 15 |
| 7a & 7b | Not usually | Mar 27–Apr 3 | Sep 23–Sep 30 |
| 8a & 8b | Not usually | Mar 11–Mar 18 | Sep 7–Sep 14 |
| 9a & 9b | Not usually | Feb 1–Feb 8 | Jul 31–Aug 7 |
| 10a & 10bFall window | Aug–Jan | Oct–Mar | ~180 days after transplanting |
Bloom dates are about 180 days after the sow or plant-out date.
Good companions
- Nasturtium: Planted at hollyhock's base, reputed to help suppress hollyhock rust, but no research or extension source was found testing this specific pairing: treat it as garden tradition, not measured evidence.
- Garlic: Planted at hollyhock's base, reputed to help suppress rust via antifungal root secretions, but no research or extension source was found testing this specific pairing: treat it as garden tradition, not measured evidence.
Where to buy hollyhock seeds
Botanical Interests · True Leaf Market · Burpee (each supplier's hollyhock seeds)
Varieties we recommend, and where to get them:
- Alcea rosea 'Nigra': Missouri Botanical Garden describes deep maroon blooms that look almost black, on rigid 5-8 foot spikes that typically don't need staking. Buy: True Leaf Market Full notes
See why we recommend these suppliers →
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See it growing
Search YouTube for "growing hollyhock" videos → (a live search, not a hand-picked video; results vary and aren't vetted by us)
← Back to the full zone 4b calendar · Plan your beds in the Garden Designer →
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Growing Hollyhock in USDA zone 4b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
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