Ageratum houstonianum

The floss flower — a neat, mound-forming annual with soft, powder-puff clusters of fluffy blue, mauve, pink or white blooms over fresh green foliage.
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Ageratum houstonianum — the floss flower

Ageratum houstonianum is the botanical name for the floss flower, a neat, mound-forming annual prized for its soft, powder-puff clusters of fluffy blue, mauve, pink or white blooms held just above fresh green foliage. It is the species behind our ageratum range within the flower seed collection.

History & origin

Native to Mexico and Central America, ageratum was taken up by gardeners for its rare, true-blue colouring — uncommon among bedding plants — and its tidy, long-flowering habit, becoming a classic edging and carpeting plant in formal summer displays.

The genus name Ageratum comes from the Greek for "not growing old," a reference to the long-lasting flowers, while the species epithet houstonianum honours the botanist and surgeon William Houstoun, who collected in Central America.

Botanical characteristics

A compact half-hardy annual, dwarf forms staying around 15-20 cm, it produces dense, brush-like flower heads in such profusion that the foliage all but disappears over a long summer season. Its low, even habit makes it ideal for edging and our ground-cover flowers, while the nectar-rich blooms draw butterflies and bees into our pollinator flowers.

Growing Ageratum houstonianum from seed

Sow under cover in early spring, pressing the fine seed onto the surface and not covering it, as light aids germination; keep warm and bright. Grow on frost-free and plant into full sun or light shade in moist, fertile soil after the last frost; deadhead or shear lightly to keep it flowering. Our flower growing guide and flower sowing calendar cover the timing.

Ready to grow floss flowers? Browse the varieties or learn the basics first.

Related categories: Ageratum · Annual Flowers · Ground-Cover Flowers · Pollinator Flowers · All Flower Seeds

At SeedsChoice, every order ships from Meppel, NL with fast, tracked EU delivery.

What is Ageratum houstonianum?
It is the botanical name for the floss flower, a tidy half-hardy annual from Central America prized for its rare, true-blue, fluffy flower clusters. How do I sow ageratum seed?
Sow under cover in early spring and press the fine seed onto the surface without covering, as light aids germination; keep warm and bright. Where is ageratum best used?
Its low, even, mounding habit makes it ideal for edging, carpeting and the front of borders, in full sun or light shade. How do I keep it flowering?
Plant in moist, fertile soil and deadhead or shear lightly through summer to keep the powder-puff blooms coming.