Four O'Clock in Zone 4a & 4b
Mirabilis jalapa
Yes, four o'clock grows in zones 4a and 4b. Plant it outside May 22–May 29.
When to plant four o'clock 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 22–May 29 |
| Estimated bloom | Jul 31–Aug 7 (~70 days after direct-sowing) |
Spacing: about 2 square feet per plant (square-foot-gardening spacing). Mature height: 2-3 ft.
Plant alongside it in zone 4b
These go outside within two weeks of four o'clock in zone 4b, so one planting day can cover them.
- NasturtiumMay 22–May 29
- MarigoldMay 22–May 29
- Ageratum (Flossflower)May 22–May 29
- Annual Geranium (Pelargonium)May 22–May 29
- Butterfly Weed (Asclepias)May 22–May 29
- Campanula (Bellflower)May 22–May 29
Four o'clocks are named for exactly what they do: the trumpet-shaped flowers, pink, red, yellow, white, or speckled bicolor, stay closed most of the day and pop open in late afternoon, releasing a strong sweet fragrance that carries into the evening. It's a low-effort plant to get started, the seed is large and easy to handle, nothing like the dust-fine seed of many other flowers, but it needs plenty of room once it's growing.
How four o'clock fits zone 4's season
Zone 4b's frost-free window runs about 128 days, from May 15 to September 20. Four o'clock needs about 70 days from sowing to first bloom.
Four O'Clock 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 |
|---|---|---|---|
| 2a & 2b | Not usually | May 27–Jun 3 | Aug 5–Aug 12 |
| 3a & 3b | Not usually | Jun 6–Jun 13 | Aug 15–Aug 22 |
| 4a & 4b (your zone) | Not usually | May 22–May 29 | Jul 31–Aug 7 |
| 5a & 5b | Not usually | May 17–May 24 | Jul 26–Aug 2 |
| 6a & 6b | Not usually | May 2–May 9 | Jul 11–Jul 18 |
| 7a & 7b | Not usually | Apr 17–Apr 24 | Jun 26–Jul 3 |
| 8a & 8b | Not usually | Apr 1–Apr 8 | Jun 10–Jun 17 |
| 9a & 9b | Not usually | Feb 22–Mar 1 | May 3–May 10 |
| 10a & 10bSpring window | Not usually | Mar–Jun | ~70 days after direct-sowing |
| 11a & 11b | Not usually | Jan 8–Jan 15 | Mar 19–Mar 26 |
Bloom dates are about 70 days after the sow or plant-out date.
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.
Good companions
No well-established companions for four o'clock.
Where to buy four o'clock seeds
Burpee (each supplier's four o'clock seeds)
Varieties we recommend, and where to get them:
- 'Broken Colors': Wisconsin Extension describes bicolor flowers with striped, splashed or marbled patterns across pink, red, white and yellow, on the standard green foliage. Buy: Botanical Interests Full notes
See why we recommend these suppliers →
As an Amazon Associate we earn from qualifying purchases. Some links on this page also go to other retailers we may earn a commission from as an affiliate, at no extra cost to you. We only recommend products with a clear consensus of positive, independent reviews, or ones we bought and use ourselves. Each item on our gear page says which.
See it growing
Search YouTube for "growing four o'clock" 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 →
Pin this for later
Growing Four O'Clock in USDA zone 4b: when to start seeds indoors, when to direct-sow, and when to expect a bloom.
Save to Pinterest