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Annual Biennial

Ageratum houstonianum 'Blue Horizon'
  • RHS AGM
  • RHS Plants for pollinators

Mexican paintbrush 'Blue Horizon'

A mound-forming annual with long-stemmed violet-blue flower-heads. Good for cutting

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Size
Ultimate height
0.1–0.5 metres
Time to ultimate height
1 year
Ultimate spread
0.1–0.5 metres
Growing conditions
Chalk
Clay
Loam
Sand
Moisture
Moist but well–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green
Summer Blue Green
Autumn Blue Green
Winter
Position
  • Full sun
Aspect

South–facing or West–facing

Exposure
Sheltered
Hardiness
H2
Botanical details
Family
Asteraceae
Native to GB / Ireland
No
Foliage
Deciduous
Habit
Bushy
Genus

Ageratum can be annuals, perennials or shrubs, usually bushy in habit, with simple ovate leaves and small fluffy blue, pink or white flower-heads in summer and autumn

Name status

Accepted

How to grow

Cultivation

This genus is ideal edging for bedding schemes; bearing weather-resistant flowers on young plants. To prolong flowering, keep soil or growing media moist.

Propagation

Propagate by seed

Suggested planting locations and garden types
  • City and courtyard gardens
  • Patio and container plants
  • Cottage and informal garden
  • Flower borders and beds
  • Garden edging
Pruning

No pruning required

Pests

Generally pest-free

Diseases

Generally disease-free

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