Guide to Growing Flossflower and Butterfly Mist

The common names for the half hardy annual Ageratum include Flossflower, Garden Ageratum, and Tropical Whiteweed. They typically flower from June to late September.

Description of Flossflower

Ageratum can grow up to 60 cm in height. The plants may have downy white, pink, deep violet or pale blue flowers. Their height and color makes them very suitable for edging as they often form compact mounds, they are also ideal border plants and look attractive in containers.


Ageratum houstonianum
Ageratum houstonianum photograph by Nemo's great uncle under creative commons licence.

Information on Ageratum and commonly grown garden species

Members of the Ageratum genus are native to central and northern America.

There are approximately sixty members of this herbaceous genera. Some of the most commonly grown species include Butterfly Mist (Ageratum corymbosum); Flossflower, Bluemink and Garden Ageratum (Ageratum houstonianum); Tropical Whiteweed (Ageratum conyzoides); Cape Sable Whiteweed (Ageratum littorale).

Quick Ageratum Growing and Care Guide

Common Names: Whiteweed, Flossflower, Butterfly Mist, Bluemink, Garden Ageratum, Tropical Whiteweed, Billy Goatweed, Cape Sable Whiteweed.
Life Cycle: Hardy annual.
Height: 6 to 48 inches (15 to 120 cm).
Native: Central and Northern America.
Growing Region: Zones 5 to 10.
Flowers: Summer and autumn.
Flower Details: Blue, lavender, purple, white, pink. Umbels. Fluffy.
Foliage: Opposite. Cordate. Oval. Serrate.
Sow Outside: Surface. Following the last frost. Spacing 6 to 16 inches (15 to 40 cm).
Sow Inside: Germination time: one to two weeks. Temperature 70 to 75°F (21 to 24°C). Seven or eight weeks in advance. Transplant outdoors a few weeks after the last frost and in summer.
Requirements: Full sunlight or partial shade. Good drainage. Soil pH 5 to 7. Rich soil. Provide plenty of water in the summer, dead heading, monthly application of fertilizer.

How to Grow Flossflower

It is best to sow Ageratum species such as Flossflower on the soil surface, with a spacing of 15 to 25 cm for smaller species and 30 cm apart for larger species after the last frost of spring. Ageratum should be grown full sunlight, but with partial shading in the hottest months of hot areas. Ageratum grows on most soils, though most species prefer a pH between 5 and 6.

They require between 5 and 14 days to germinate. If initiating growth indoors then it is best to sow at a temperature of 21 to 24 degrees centigrade six to eight weeks before transferring outdoors in spring; after the last frost, or in late summer.

Caring for Ageratum in the Garden

Ageratum species such as ageratum conyzoides are easy to look after and requires watering only at the height of the summer, it is advisable to fertilise monthly and to remove Ageratum flower by deadheading.

Information on Commonly Grown Ageratum Garden Species

Flossflower (Ageratum houstonianum)
The flossflower is an annual Ageratum species, that can range in height from 12 to 39 inches (30 to 100cm). The leaves of the plant are oval at the stem and triangulate out, reaching a length of 1 to 3 inches (2.5 to 7.5 cm). The flowers are usually blue, but as there are many varieties of flossflower available other colors are common, especially purple, white, or pink. The plant takes its name from the floss like flowers that it carries.

As a native to Mexico the flossflower should be grown in areas that receive lots of sun; In very hot areas they also grow well in partially shaded conditions. It usually flowers throughout summer through to the first frost of autumn.

Butterfly Mist (Ageratum corymbosum)
This is a perennial garden plant that likes tropical conditions, in the USA it can grow in zones 8 to 11. The plant reaches an height of between two to four feet (60 to 120cm) depending on species. The seeds should be sown on the soil surface at a distance of 3 to 4 feet (90 to 120cm) and require a soil pH of 5.5 to 7.5. Grow in full sunlight, or in partial shade in very hot areas. The flowers of butterfly mist are light blue in color.

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