Ageratum houstonianum

Ageratum (Floss Flower)

Taxonomy

Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Ageratum
Species: Ageratum houstonianum (most common ornamental species)

Common Names by Region

• North America: Floss Flower, Blue Mink, Pussyfoot
• Central & South America: Ageratum, Tropical Floss Flower
• Other: Mexican Ageratum, Bluemink

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Description

Growth Habit

Compact, bushy annual forming dense mounds of soft, tufted flower clusters. Well suited to mass plantings and container culture.

Size

Typically grows 6–12 inches (15–30 cm) tall, spreading 6–18 inches depending on cultivar and growing conditions.

Leaves

• Oval to heart-shaped
• Opposite arrangement along stems
• Soft texture with fine hairs
• Bright to medium green coloration

Flowers

• Tufted, thread-like florets forming rounded clusters
• Colors include blue, lavender, purple, pink, and white
• Blooms continuously from late spring until frost
• Notable for producing true blue tones, uncommon among annual flowers

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Known Range

Native Range

Native to Central America and parts of Mexico.

Cultivated Range

Widely grown across North America as a bedding annual. Common in:

• Borders
• Pollinator gardens
• Containers
• Mass plantings

Not considered invasive in northern climates due to frost sensitivity.

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Care & Habitat

Light

Prefers full sun to partial shade. Strongest flowering occurs in full sun.

Water

Moderate water requirements. Performs best in consistently moist, well-drained soil. Mulching helps retain moisture during hot periods.

Soil

Adaptable, but thrives in rich, well-draining soil with a neutral to slightly acidic pH.

Humidity

Tolerates moderate to high humidity. Dense plantings may require airflow to prevent disease.

Temperature

• Grown as an annual
• Not frost tolerant
• Performs best in warm summer conditions
• Suitable as a seasonal bedding plant in USDA Zones 2–11

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Propagation

Primarily grown from seed.

• Start indoors 6–8 weeks before last frost
• Transplants easily
• Establishes quickly in warm soil
• Some varieties may self-seed lightly

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Pests, Diseases, & Threats

Generally resilient.

• Occasionally affected by aphids, spider mites, or whiteflies
• Susceptible to root rot in poorly drained soils
• Powdery mildew may occur in dense plantings with low airflow

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Additional Notes

Special Characteristics

• Long-blooming and reliable
• Provides rare blue coloration to garden palettes
• Attracts butterflies and small pollinators
• Deer-resistant due to aromatic foliage

Maintenance & Management

Low maintenance.

• Deadheading optional; many modern cultivars are self-cleaning
• Pinching young plants encourages fuller, bushier growth

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A Note from the Cernunnos Foundation

At the Cernunnos Foundation, plant profiles are treated as more than ornamental guides. They are records of how living systems behave when placed into human-designed environments.

Ageratum is a useful reminder that resilience does not require complexity. It thrives because it is well-matched to its conditions, offers consistent output, and asks little in return.

In a time when many systems are over-optimized and under-designed for durability, even a modest bedding annual can illustrate a broader principle:

Design for stability.
Value reliability.
Work with systems, not against them.

These lessons apply as much to gardens as they do to the larger ecological and civic systems we depend on every day.