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Almanac Planting Co Ageratum houstonianum 'Red Flint' Flower Image
Almanac Planting Co Ageratum houstonianum 'Red Flint' Plant and Flower Image
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Ageratum 'Red Flint'

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Ageratum houstonianum 'Red Flint'


Uses: Annual flowering plant 

Benefits: Easy to take care of. Produces pinkish-purple flowers that typically start in June and last until frost. 

Zones: 3 - 10

Sun: Full

Life Cycle: Annual

Mature Height: 24"

Mature Width: 12"


Ageratum houstonianum 'Red Flint'—commonly known as Red Flint Floss Flower—is a medium size, frost-tender annual that's best known for its clusters of lovely, fluffy flowers which resemble asters. Flower production is typically constant from late-spring until mid-fall. 

'Red Flint' is an average height cultivar of Ageratum houstonianum, making it especially well suited for as an all around annual, and for potted uses. Its flowers are atop long stems which make them great for cut flower production.

Produces flowers that are predominately shades of red, pink, and purple; however, the potential for blue and white blooms also exists.  

Growing in a shapely mound, it produces larger flowers than traditional ageratums, which it supports via its strong, sturdy, tall stems. 

Ageratums are known to attract various pollinators such as bees and butterflies. 


Floss Flower Care

Plant after the last spring frost, ideally when temperatures are above 50°F.

Fertilize as required, especially if planted in poor soil. 

Ageratum houstonianum 'Red Flint' does best in full sun, although partial shade is also acceptable. The plant may benefit if very strong afternoon sun is blocked by a source of partial shade, especially in hot, dry areas. 

Although unnecessary, the deadheading of spent flowers will encourage blooming, and help to ensure a tidy plant. 

Floss Flower requires soil that is moist, but not wet. Irrigate during establishment, and during periods of drought. Do not allow this plant's soil to completely dry! Avoid overhead watering to mitigate the risk of powdery mildew. 

Does best in temperatures between 65°F and 95°F.


Size of Floss Flower for Sale

The Ageratum houstonianum 'Red Flint' that we sell online will ship in a 4" grow pot. Each plant will be appropriately sized for its pot. 

Size of Floss Flower When Fully Grown

Ageratum houstonianum 'Red Flint' typically grows to a height of 24" and a width of 12". It sometimes grows as small as 12" tall and 6" wide.

Additional Information

Common Names of Ageratum houstonianum 'Red Flint'

  • Floss Flower 'Red Flint'

  • Ageratum 'Red Flint'

Toxicity and Risks of Floss Flower

All parts of Ageratum houstonianum 'Red Flint' are considered toxic if ingested. This is due to the fact that they contain pyrrolizidine alkaloids, which is known to cause liver lesions.