Ageratum Houstonianum for Monarch Butterflies

Ageratum houstonianum common names: Blue Horizon, Floss Flower, Mexican Paintbrush ‘Blue Horizon’

monarch female sea of ageratum houstonianum ageratum houstonianum
Monarch Female on Floss Flower

Ageratum Houstonianum Plant Specs

  • Herbaceous perennial flower for USDA hardiness zones 2a-11b (lows -46° C or -50° F)
  • Native plant to Central and South America
  • Fast growing annual ageratum and reseeds generously in our northern garden
  • Full sun to light shade
  • Height: 1.5 to 3 ft feet
  • Spacing: 1 to 2 feet
  • Disk Flowers
  • Flower color: light purple, violet, blue-purple, red, white
  • Leaves: opposite, wide, heart-shaped
  • Stems: thin, upright, bendable
  • Blooms summer through first frost (Jul, Aug, Sep, Oct)

Floss Flower Pros

  • Long flowering period- monarchs seek this out all season
  • A short “filler” plant that works well between some of your showier flowers
  • Care-free plant
  • grows quickly from seed and reseeds
  • Favorite nectar source of monarchs
  • Provides migration energy for masses of monarchs

Floss Flower Cons

  • Can be invasive with seeding and underground rhizomes, but easy to pull
  • Blue Horizon floss flower spreads by excessive seeding
  • Flowers aren’t showy
  • Susceptible to White Flies and Powdery Mildew

Looking for an ageratum perennial better-suited for southern states? Try migration favorite Conoclinium greggii (Gregg’s mistflower)

How to ID two monarch magnet ageratums? Look at their leaves. Find out more about these monarch butterfly plants...

Floss Flower Plant Propagation

Worn Monarch Female Refuels in Top Ageratum for monarchs- Floss Flower
Blue HORIZON

Mexican Ageratum Growing Tips

  • In Minnesota, we pull our ‘blue horizon’ floss flower plants in the fall and let them come back from seed the next season. This keeps the rhizomes from taking over the garden, and the seedlings grow quickly each spring
  • Good option moist meadows and wildflower gardens…will grow in clay soils

Pollinator Plus

Ageratum houstonianum also attracts bees, moths, painted ladies, skippers, and queen butterflies.

Buy Ageratum Houstonianum Plants and Seeds

As difficult as the botanical name is to spell and say, always purchase plants searching for this name. Common names are more often misused when labeling plants, so you’ll have best results searching for:

1. Find Ageratum houstonianum ‘blue horizon’ on Etsy (rarely available…look specifically for A. houstonianum ‘blue horizon’….other varieties rarely attract butterflies)

If you’re interested in adding more butterfly plants to your garden, check out our butterfly flowers page

Please post below if you have any questions or comments about growing
Ageratum houstonianum aka Floss Flower in your garden:
Share the Joy of Butterflies