Hardiness zones
Sunset All
USDA All
Landscape Use: Border edging, cool season bedding plant in Phoenix, Warm season in the eastern US, short lived landscape perennial along the west coast; great for container gardens.
Form & Character: Short, diminutive perennial mostly treated as an annual in the landscape.
Growth Habit: Medium growth rate to 6 to 24 " tall. Most cultivars form a dense mound.
Foliage/Texture: Small, opposite, light green leaves, ovate to 1" long, crenate margins, medium fine texture
Flowers & Fruits: Terminal clusters of 1/4 to 1/2" flower heads in cymose clusters without ray flowers. Flower colors range from white, pink, burgundy, blue, mauve, and purple, fruit inconspicuous.
Seasonal Color: Anytime in bloom
Temperature: Best in the 40 to 85oF range.
Light: Full sun
Soil: Well drained and organic. Easily becomes chlorotic in sandy soils.
Watering: Regular
Pruning: None except to remove spent flowers.
Propagation: Seed which germinate in 5 days, cutting.
Disease and pests: Red spider mites, white fly, powdery mildew and botrytis on flowers.
Additional comments: "Ageratum" means not growing old (referring to the persistent flowers), though the day of its popularity in Phoenix as a winter bedding plant seems to have 'died' several years ago. "Houstonianum" is named after botanist Dr. W. Houston who brought floss flower plants back from Mexico and the West Indies. There are many named cultivars with flower colors rangin from powder blue and white to mauve and deep blue and from pink lavender to deep burgundy red. Floss flower takes 600 to 100 days are germination to bloom. Plant out in late September in Phoenix for winter show.