James H. Schutte
Family
Asteraceae
Botanical Name
Ageratum
Plant Common Name
Flossflower
General Description
There are approximately 40 species in the genus Ageratum. All are characterized by their clusters of small, showy, fluffy, flowerheads. The variable species may be annuals or perennials and are naturally distributed across the tropical and subtropical regions of the United States, Mexico and Central America. They are found in diverse habitats from woodlands to grasslands. According to the Global Compendium of Weeds, several species, such as Ageratum conyzoides and the ornamental Ageratum houstonianum, have escaped from cultivation and become a problematic weed Hawaii, Australia and Africa.
Ageratum may be herbaceous or semi-woody and are typically clump-forming and mounding. Some spread by rhizomes. The upright stems are usually branched and lined with triangular, oval, elliptical or linear leaves. The hairy or smooth leaves are often fragrant, due to the oil-filled glands that dot their surface. Bloom times vary widely. Abundant flowerheads are borne at the ends of the stems in branched clusters. Each fuzzy head is composed of many tubular, funnel-shaped flowers. The blooms may be lavender-blue, white, pink, or violet and attract bees, butterflies and other insect pollinators. Mature heads are filled with fruits that resemble small sunflower seeds topped with feathery hairs to facilitate wind dispersal.
Only a few species are favored for garden use, but there are lots of wonderful hybrid cultivars to choose from. The most popular species is blue mist flower (Ageratum houstonianum), a tender perennial bedding plant favored in both temperate and tropical zones. This low-growing, evergreen Mexican native has a dense, bushy habit and produces numerous lavender-blue, purple, pink or white flowers all season long. Grown mostly as an annual, this is among the easiest of garden flowers to grow. Most cultivated varieties are hybrids of this species. Two exceptional hybrids include the tall, white-flowered ‘Bouquet White’ and compact and cool, ‘Blue Mink.’
Garden grown selections thrive in full to partial sun and fertile garden soil with good drainage. They are easily planted by seed and should be planted outdoors after the danger of frost has past. In hot, humid locations, they are often grown as winter annuals and may benefit from some afternoon shade. In frost free zones some perform as short-lived perennials. Stems may be pinched early in the season for increased flower production. Ageratum is terrific for beds, borders, containers and edging.
