Blue Horizon Ageratum (Ageratum houstonianum) | Butterfly Plant

Description

Commonly known as:
Blue Horizon Ageratum, Floss Flower, Blue Floss Flower

Description of Plant:
Ageratum houstonianum ‘Blue Horizon’ is a beautiful flowering plant known for its fluffy, lavender-blue blooms and soft green foliage. Unlike compact ageratum varieties, Blue Horizon produces tall, sturdy stems that make excellent cut flowers. From late spring through fall, its abundant blooms attract butterflies, bees, and other beneficial pollinators. In addition, its long flowering season brings vibrant color to Southern California gardens and floral arrangements.

Growth Habit:
This upright, bushy plant typically grows 24–30 inches tall and 12–18 inches wide. Its branching stems produce clusters of soft, fuzzy flowers that rise above the foliage.

Watering Instructions:
Water regularly during establishment and throughout the growing season. Keep the soil moderately moist but not soggy. During hot Southern California summers, deep watering helps maintain healthy growth and continuous flowering.

Soil Needs:
Prefers fertile, well-draining soil enriched with compost or organic matter. However, it adapts to average garden soils as long as drainage remains good.

Sun Requirements:
Thrives in full sun to partial shade. Along the coast, full sun encourages abundant flowering. In hotter inland areas, afternoon shade helps protect plants from intense summer heat.

Indoor or Outdoor Tips:
Best grown outdoors in butterfly gardens, cottage gardens, cutting gardens, borders, and large containers. Harvest flower stems regularly for bouquets, and remove spent blooms to encourage additional flowering.

Perennial or Annual:
Typically grown as an annual in Southern California. Although botanically a tender perennial, frost can damage or kill plants during winter.

Additional Tips:
Blue Horizon Ageratum is especially attractive to butterflies, including monarchs, skippers, and other nectar-feeding species. Bees also visit its abundant flowers. In addition, its tall stems and long-lasting blooms make it an excellent choice for fresh-cut flower arrangements. Safety: Ageratum contains compounds that can be toxic if ingested, so keep it away from pets and livestock that may browse plants.