Hardy Ageratum
Conoclinium coelestinum
Fluffy blue-violet flowers in September and October, a rare cool color in the fall garden. Spreads readily to fill wet slopes and rain gardens.
Typically 1 pint–1 gal · $9–$30 · final price at pickup
- Thu, Aug 138 AM – 4 PM
- Fri, Aug 148 AM – 4 PM
- Sat, Aug 158 AM – 2 PM
One of very few native perennials offering true blue-violet in October.
Hardy Ageratum looks like the bedding annual ageratum, but it blooms in fall when everything else is winding down, and it comes back year after year. The fluffy blue-violet flowers appear in September and October, sometimes lasting until hard frost, filling the garden with cool color at exactly the moment warm-season annuals give out. The blooms draw late-season skippers, sulphurs, and small native bees that are building reserves for winter. It spreads assertively by both rhizomes and self-seeding: that's a feature, not a bug, if you want it to naturalize along a wet slope or fill gaps in a rain garden. In tighter spaces, simply pull seedlings or divide clumps in spring to keep it in check. The blue color is rare in fall natives and makes it a valuable design element for extending the season.
A nursery-grown plant, ready for the ground.
Healthy, container-grown hardy ageratum propagated on-site at Hill House from regional genetics. Includes a one-page care card. We make every effort to supply plants as listed; occasionally we substitute a similar species of equal value.
- Sun
- Full sun
- Water
- Average
- Mature size
- 1.5–2 ft · 24–36 in wide
- Bloom time
- Fall
- USDA zones
- 5–9
- Family
- Asteraceae
- Native range
- Eastern and central United States, from New Jersey south to Florida, west to Nebraska
Care notes for hardy ageratum.
Plant in full sun to part shade in moist to average soil. Tolerates wet conditions. Cut back in early spring before new growth emerges. Divide every 2-3 years to manage spread. Can be aggressive. site it where spread is welcome or install a root barrier.
Pairs well with these.
Same light, same soil, same wildlife. Janet's picks to plant alongside hardy ageratum.
Or skip the guesswork.
Curated packages bundle complementary species for an instant habitat. One reservation, one pickup day, a printed layout map.
Short on Space Package
For gardeners who have an abundance of passion but are short on space, this package features tidy, upright, clump-forming natives that behave and function well in small spaces.
Shade Bed Package
Ferns, sedges, and woodland natives that thrive under existing trees.
Birder’s Paradise Package
For the avid bird watchers and budding ornithologists in our community, the Birder’s Paradise Package consists of species that Hill House Nursery staff and longtime native plant advocates such as Doug Tallamy consider ‘premier bird garden plants’.