Ageratum houstonianum 'City Blue'

Name: Ageratum 'City Blue' – Tall Blue Annual Flower for Borders
Brand: Ageratum
SKU: pda686
Price: 4.9 EUR
Availability: InStock

€4,90

Organic

Sustainable

Locally grown

Ageratum houstonianum 'City Blue' is a fluffy blue, frost-tender perennial grown as an annual in most climates.

The flowers take the form of large fluffy clusters in a soft, powdery light mauve-blue.

The leaves are hairy, toothed, and oval in shape, sometimes heart-shaped at the base, with a soft green hue.

The sturdy stems of this generous variety make it ideal for adding height to borders or for creating long-lasting bouquets.

From April through early autumn, flowers bloom continuously - deadheading helps the plant to continue to produce the pompom flowers.

NOTA BENE: Ageratum is not reliably perennial in most European gardens. It is botanically classified as a tender perennial— meaning it survives year-round only where winter temperatures never drop below –1°C.

This distinction isn’t semantic: mislabeling ageratum as “perennial” leads gardeners to skip overwintering steps, abandon succession planting, or misdiagnose winter dieback as disease. True perennials regrow from persistent roots or crowns each spring; ageratum lacks cold-hardy rootstock and dies completely when exposed to sustained freezing. Yet its long bloom window (14–20 weeks), heat tolerance, and pollinator appeal make it indispensable—even if you replant it every year.

Flowering	June, July, August, September, October
Flower Color	Blue
Exposure	Full Sun
Frost Tolerance	-4°C
Size	60cm H x 60cm W
Soil	Cool
Origin	Central America
Planting Season	March to May, September to November

pda686

€4,90

In stock

🪴9x9 cm

🚂 Ships across EU
🌱 Grown in our nursery

💦 High drought tolerance once established: Hairy, silvery leaves reduce water loss and help the plant survive dry conditions.
☀️ Sun-loving: Performs best in full sun but tolerates partial shade.
👍 Low-maintenance: Aromatic foliage deters some pests, and the plant requires minimal care.
🌸 Long flowering period: Ensures continuous visual impact and nectar supply for several weeks.
💪 Self-supporting, compact habit: Ideal for front-of-border planting, rockeries, and container use.

Tender perennial - mulch heavily in the southern zones of Europe. In the north, bring inside during the frosty months.
Ageratum does not divide well. Its fibrous roots lack storage capacity, and division almost always fails. Instead, take softwood cuttings:
Alternatively - collect the seeds!

Ageratum 'City Blue' is a cultivar resulting from extensive selective breeding of Ageratum houstonianum, the Mexican ageratum. This species belongs to the Asteraceae family and is native to Central America and the Caribbean.

Floral Morphology

The flower heads are borne in dense corymbs. The ray flowers are threadlike and fluff-haired, leading to the common name. The narrow lanceolate bracts are pointed, denticulate only at the top and glandular hairy. The flowering period is from May to November in the northern hemisphere.

The plant attracts butterflies.

Perennial vs Annual Life Cycle of the Ageratum

Ageratum is derived from the Greek “a geras,” meaning non-aging, referring to the longevity of the flowers. This makes them fantastic additions to bouquets and dry flower arrangements.

Ageratum has evolved a unique method of protecting itself from insects: it produces a methoprene-like compound which interferes with the normal function of the corpus allatum, the organ responsible for secreting juvenile hormone during insect growth and development. This chemical triggers the next molting cycle to prematurely develop adult structures, and can render most insects sterile if ingested in large enough quantities,