Botanical Name: Ageratum houstonianum ‘Blue Horizon’ 

Common Name: Floss Flower 

Hardiness Zone: Grown as an Annual in Most Climates (USDA Zones 2–11) 

Size: 18–24" Tall × 18–24" Wide 

Growth Habit: Upright, Well-Branched, Full Habit 

Sunlight: Full Sun to Partial Sun 

Soil: Well-Drained, Moderately Fertile Soil 

Water Needs: Moderate; Consistent Moisture Encourages Best Blooming 

Bloom Season: Late Spring Through Frost 

Fertilizer: Light, Regular Feeding During the Growing Season 

Features: Clear Blue Flower Clusters, Tall Stems, Strong Garden Presence, Pollinator Friendly 

Uses: Excellent for Annual Beds, Mixed Borders, Pollinator Gardens, and Large Containers 

Patent: ✔ Patented 

Plant Patent: PP36,798 

Propagation: ❌ Propagation Prohibited Without License

See our complete Ageratum Plant Guide for full care details.

More About Ageratum ‘Blue Horizon’

Ageratum ‘Blue Horizon’ is a modern, tall-growing floss flower selected for its improved height, strong branching, and large, airy flower clusters. Its soft blue blooms rise above the foliage, creating a light, cloud-like effect that adds vertical interest without heaviness. This variety moves beyond the traditional low-growing ageratums, offering a more substantial presence in the landscape.

Blooming steadily from late spring through frost, ‘Blue Horizon’ produces generous flower heads that attract bees, butterflies, and other beneficial pollinators. The consistent flowering habit ensures reliable color throughout the season, making it an excellent choice for gardeners looking to maintain visual interest during the hottest months of summer.

Why We Like It (Our Trials)

In our trials, ‘Blue Horizon’ has shown excellent garden performance with strong stems that hold flowers upright even in heat and humidity. Plants remain full and balanced with regular watering and light feeding, avoiding the legginess sometimes seen in older ageratum varieties.

We also appreciate how easily it integrates into a wide range of garden designs. Pollinators are frequent visitors, and the tall flower clusters add movement and texture to beds and borders. Whether used in pollinator-focused plantings or mixed annual displays, ‘Blue Horizon’ consistently delivers dependable color and structure.

‘Blue Horizon’ vs. Other Ageratum

Compared to other compact Ageratum like Aloha® Blue and traditional edging types, ‘Blue Horizon’ delivers significantly more height, broader spread, and larger, airier flower clusters that create real presence in the landscape. ‘Monarch Magic’ is bred primarily for maximum pollinator attraction with bold, elevated blooms, while ‘Blue Horizon’ strikes a balance—offering upright structure, strong branching, and a lighter, more open flower display that reads beautifully from a distance.

For gardeners who want a Floss Flower that adds vertical interest, steady color, and pollinator activity without the bulk or tight form of dwarf selections, Ageratum ‘Blue Horizon’ is an excellent choice for mixed beds, mass plantings, and modern garden designs.