annual

Flower-of-an-hour

The Story

Plant Bio

Hibiscus trionum, commonly known as flower-of-an-hour, is a low-growing herbaceous annual or short-lived perennial forming a branched, mounding bush from a deep taproot. The dark green leaves are palmately divided into coarsely toothed lobes, providing a textured backdrop for solitary flowers that open for only a few hours on sunny days.

Each cream to pale yellow blossom features a deep maroon to black center and is followed by an inflated, bladder-like calyx that resembles a paper lantern. These hairy, translucent seed pods dry on the plant and release numerous seeds, allowing the species to self-sow aggressively in warm soils.

Uses & Benefits:

Features unique, short-lived cream flowers with dark centers, followed by decorative, bladder-like seed pods.

Serves as a fast-growing annual ground cover or temporary filler in sunny, open garden beds.

Attracts native bees and general insect pollinators to its iridescent petals.

Essentials

At a Glance

Plant Type

Annual

Height

40"

Width

40"

Light

Full Sun

Zones

4, 5, 6, 7, 8, 9, 10

Water

Moderate

Humidity

Wide range

Lifespan

Annual or short-lived perennial

Native To

Old World tropics and subtropics

Toxicity

Non-toxic (hairs cause mild skin irritation)

Bloom period

Summer – Autumn

In flower about 6 months of the year

Planting

How to Grow

Select a planting site in full sun with fertile, humus-rich, well-drained soil.
Sow seeds directly into warm soil after the last frost, pressing them lightly into the surface.
Water regularly to keep the soil moist but not waterlogged while the taproot establishes.
Apply a balanced general-purpose fertilizer sparingly in spring to avoid excessive foliage growth at the expense of blooms.

Pro Tip

Deadhead spent flowers daily before the inflated calyces mature and dry; failure to remove these pods leads to prolific self-seeding that can quickly overwhelm garden beds.

Keep It Thriving

Care Guide

Do

Deadhead regularly to control aggressive self-seeding.
Wear gloves when handling the plant to avoid skin irritation from fine hairs.
Grow in full sun to maximize the brief daily flowering window.
Ensure the soil is well-drained to prevent root rot.

Don't

Do not over-fertilize, as excess nutrients promote foliage at the expense of flowers.
Do not prune back into old, leafless wood.
Do not allow seed pods to dry on the plant if you wish to prevent spreading.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Deadhead
Fertilize
Pest Check
Plant
Propagate

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Cottage gardensRock gardensWildflower meadowsAnnual borders

Companion Plants

Althaea officinalis

Multiply

Propagation Methods

Good to Know

Common Questions

Flower-of-an-hour questions

What zones can Flower-of-an-hour grow in?

Flower-of-an-hour is hardy in USDA Zones 4–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

Is Flower-of-an-hour deer resistant?

Not reliably. Deer may browse Flower-of-an-hour, especially tender spring growth — plan on repellents or fencing where pressure is high.

When does Flower-of-an-hour bloom?

Flower-of-an-hour typically blooms in summer through autumn. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Flower-of-an-hour need full sun?

Flower-of-an-hour does best in full sun (6+ hours).

Is Flower-of-an-hour drought tolerant?

Yes — once established (usually after the first full season), Flower-of-an-hour handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.