Ageratum
Family Asteraceae — Genus Ageratum
Ageratum, commonly known as floss flower, is a popular bedding annual cherished for its soft, fluffy flower clusters in true blue shades rarely found in the annual plant world. Native to tropical regions of Central America and Mexico, ageratum provides long-lasting color from late spring until frost kills the plant. Its compact, mounding habit and continuous bloom make it one of the most reliable edging and container plants available.
Quick Facts
Bloom Time
Ageratum flowers continuously from late spring until the first killing frost, producing fluffy, powder-puff flower clusters in shades of blue, purple, pink, and white. The soft, fuzzy texture of the flowers is unique among bedding plants and provides excellent contrast against bolder blooms.
Size and Growth Habit
Ageratum grows 6 inches to 2 feet tall depending on cultivar, with a compact, mounding habit. Dwarf varieties (6 to 8 inches) are ideal for edging, while taller selections work well in mixed borders and cutting gardens. Heart-shaped, fuzzy leaves provide attractive green foliage beneath the flower clusters.
Hardiness Zones
Ageratum is grown as an annual in all zones. It is frost-tender and killed by the first hard freeze. In its native tropical range (Zone 10 through 11), it behaves as a tender perennial.
Light Requirements
Ageratum performs best in full sun to light shade. In hot climates (Zone 8+), afternoon shade extends bloom period and prevents flower fading. In northern gardens, full sun produces the most compact growth and heaviest flowering.
Soil and Water Requirements
Grow ageratum in moist, well-drained, fertile soil. It has moderate water needs and should not be allowed to dry out completely, which causes stunting and poor flowering. Equally, avoid waterlogged conditions. Regular watering produces the best results.
Pruning
Ageratum is largely self-cleaning, but light shearing or deadheading of spent flower clusters promotes fresh bloom flushes and maintains a tidy appearance. Tall varieties may benefit from pinching early in the season to encourage bushier growth.
Summer Care
Keep soil consistently moist. Feed every 2 to 3 weeks with balanced liquid fertilizer. Ageratum handles summer heat well but appreciates afternoon shade in the hottest climates. Watch for spider mites in very hot, dry conditions.
Winter Care
Ageratum does not survive frost. Pull plants after they are killed by cold and compost. In frost-free climates, ageratum may persist as a short-lived perennial.
Companion Plants
Pests and Diseases
- Whitefly: Common pest, especially in greenhouse production. Use yellow sticky traps and insecticidal soap.
- Spider mites: Occur in hot, dry conditions. Mist plants and treat with miticide if needed.
- Powdery mildew: Can develop in humid conditions with poor air circulation.
Common Varieties
Toxicity
Mildly toxic — use cautionAgeratum contains pyrrolizidine alkaloids that are mildly toxic if ingested. While casual contact is safe, consumption of plant material can cause liver damage over time. Keep away from grazing livestock. Not recommended for planting near vegetable gardens where accidental ingestion might occur.
Care Difficulty
Ageratum is one of the easiest annuals to grow. Regular watering and occasional feeding produce continuous bloom from planting until frost. It is an excellent choice for beginning gardeners looking for reliable, long-lasting color.