How to Grow Four O'Clock: Planting, Spacing, Care & Bloom
Quick answer
Direct sow or transplant after last frost. Start indoors −8 to −4 (WI up to 8 weeks; Cornell 4–6). NC State Low poison severity — roots and seeds; contact dermatitis possible from roots.
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Updated
Safety: NC State poison severity Low for Mirabilis jalapa. Symptoms: stomach pain, nausea, vomiting, diarrhea; handling roots may cause dermatitis. Poison parts: roots, seeds. Contact dermatitis: yes. Do not eat roots/seeds; wash hands after handling tubers; keep from children/pets. Not medical advice. (NC State Mirabilis jalapa; Wisconsin four o'clocks)
Four o'clock (Mirabilis jalapa) — tender perennial grown as an annual.
Sourced from university extension guides. For dates where you live, use the ZIP planting planner.
Planting timing
Wisconsin: seed outdoors after the danger of frost has passed, or indoors up to 8 weeks ahead; set transplants out after all frost risk — about when you plant tomatoes. Dig tubers before first freeze; replant after last frost. (Wisconsin four o'clocks) Cornell: sow outdoors after last frost, or start indoors 4 to 6 weeks before last frost. (Cornell four o'clock) Planner: Start indoors last frost −8 to −4; Direct sow / Transplant last frost 0.
Depth and spacing
WI: seed about ¼ inch deep; thin/transplants 12–24 inches apart; germination 5–7 days at about 68–70°F. NC: height 1.5–4 ft; width 1–2 ft.
Sun, soil and water
Full sun to partial shade; humus-rich well-drained soil; moderate moisture; drought tolerant once established (Cornell/WI/NC).
Care
Soak or nick seeds (WI/NC). Dig/store tubers in cold zones like dahlias — peer method on dig-store dahlias & cannas. Self-seeds vigorously; can be weedy (NC).
Bloom
Flowers open late afternoon/evening; summer through frost (WI/Cornell). No single days-to-bloom integer sourced.
Pests and diseases
NC/WI: no significant problems / few pests. Usually none needed.
Related: dig-store dahlias & cannas · ZIP planner
Frequently asked questions
When do I plant four o'clocks?
Direct sow or transplant after last frost. Start indoors −8 to −4.
Are four o'clocks poisonous?
Yes — Low severity; roots and seeds (NC State). Contact dermatitis possible from roots.
Can I save the tubers?
Yes in cold zones — dig before freeze and replant after last frost (WI/NC).
Sources
- NC State Extension: NC State Mirabilis jalapa
- University of Wisconsin–Madison Extension: Wisconsin four o'clocks
- Cornell University CALS: Cornell four o'clock