What Is 4 o'clocks

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Last updated: April 17, 2026

Quick Answer: 4 o'clocks, or Mirabilis jalapa, are flowering plants known for blooming in late afternoon. Native to tropical Americas, they typically open around 4 PM and close by morning. The plant was first scientifically described in 1753 by Carl Linnaeus.

Key Facts

4 o'clocks were formally classified by Carl Linnaeus in 1753 under the name Mirabilis jalapa.
The flowers commonly open around 4 PM, which inspired their common name.
4 o'clocks are native to tropical regions of Central and South America.
Plants can grow up to <strong>3 feet tall</strong> and spread <strong>2–3 feet wide</strong>.
They produce a wide range of flower colors, including pink, yellow, white, and red, often on the same plant.

Overview

4 o'clocks, scientifically known as Mirabilis jalapa, are ornamental flowering plants prized for their vibrant, fragrant blooms that open in the late afternoon. Commonly found in gardens across warm climates, they are prized for their ease of cultivation and long blooming season from early summer to fall frost.

These perennials are often grown as annuals in temperate zones and are notable for their ability to self-seed prolifically. Their name comes from the habit of flowers unfurling around 4 PM, although bloom time can vary slightly based on temperature and light exposure.

Bloom time: Flowers typically open between 4:00 and 5:00 PM, remaining open overnight and closing by mid-morning the next day.
Origin: Native to the tropical regions of Peru and Central America, 4 o'clocks were introduced to Europe in the 18th century.
Height: Mature plants reach 2 to 3 feet in height, with some specimens growing up to 4 feet under ideal conditions.
Flower variety: Individual plants often produce multiple flower colors, including pink, yellow, red, white, and striped variations.
Toxicity: All parts of the plant contain low levels of alkaloids, making them mildly toxic if ingested in large quantities.

How It Works

The growth and flowering behavior of 4 o'clocks are influenced by circadian rhythms and environmental cues like light and temperature. Their unique bloom cycle makes them a favorite among gardeners seeking evening interest.

Photoperiodism:Flowers respond to decreasing light levels in late afternoon, triggering bloom opening; this mechanism helps attract nocturnal pollinators like moths.
Seed germination:Seeds sprout in 5–7 days when soil temperatures exceed 65°F (18°C), with full maturity reached in 90–120 days.
Root system: Develops a thick, tuberous root that allows the plant to survive mild winters in USDA zones 7–11.
Fragrance: Blooms emit a sweet, jasmine-like scent strongest at dusk, enhancing appeal to pollinators and garden visitors.
Self-seeding:Plants readily reseed due to high seed production, often returning year after year without replanting.
Color variation: Exhibits genetic instability in flower pigmentation, leading to multiple colors on a single plant.

Comparison at a Glance

Below is a comparison of 4 o'clocks with other common garden flowers based on key characteristics.

Plant	Bloom Time	Height	Hardiness Zone	Flower Colors
4 o'clocks	4 PM – morning	2–3 ft	7–11	Pink, yellow, red, white, striped
Morning glory	Dawn – late morning	6–10 ft (vine)	10–12	Blue, purple, white, pink
Marigold	Full day	6–36 in	Annual	Yellow, orange, red
Night-blooming jasmine	Evening	3–10 ft	9–11	White
Daylily	Daytime	1–4 ft	3–9	Yellow, orange, red, pink

This table highlights how 4 o'clocks occupy a unique niche with their afternoon bloom time and colorful, fragrant flowers. Unlike many day-blooming species, they extend garden beauty into the evening hours.

Why It Matters

4 o'clocks play a valuable role in horticulture and ecological gardening due to their pollinator appeal and low maintenance. Their ability to thrive in poor soils and withstand heat makes them ideal for beginner gardeners.

Pollinator support: Attracts moths and hummingbirds during evening hours, supplementing daytime pollination networks.
Urban gardening:Thrives in containers and small spaces, making it suitable for patios and balconies.
Low water needs: Requires minimal irrigation once established, ideal for xeriscaping.
Educational value: Used in schools to teach plant circadian rhythms and genetics due to color variation.
Cultural significance: Known as "maravilla" in Spanish-speaking countries, symbolizing surprise and wonder.
Historical use: Used in traditional medicine for anti-inflammatory and antifungal properties, though not widely clinically validated.