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Ageratum houstonianum ‘Blue Horizon’ (Floss Flower)

Ageratum 'Blue Horizon', Floss Flower 'Blue Horizon', Mexican Paintbrush 'Blue Horizon'

AGM Award
Floss Flower 'Blue Horizon', Ageratum Houstonianum 'Blue Horizon', Ageratum Blue Horizon, Blue flowers, Blue annuals

One of the tallest, Ageratum houstonianum ‘Blue Horizon’ (Floss Flower) is a frost-tender annual boasting fluffy lavender to purplish-blue flower clusters, up to 3 in. across (7 cm), from late spring to frost. Attractive to butterflies, the blossoms are borne on long, sturdy stems and float above the neat foliage mound of heart-shaped leaves. Best used for edging or borders of beds or in containers. Great for cutting.

  • Recipient of the prestigious Award of Garden Merit of the Royal Horticultural Society.
  • Grows up to 18-30 in. tall (45-75 cm) and 12-18 in. wide (30-45 cm)
  • Performs best in full sun in rich, moist, well-drained soils. Appreciates some light afternoon shade in hot summer climates. Provide consistent moisture throughout the growing season.
  • Excellent choice for beds and borders, edging, city gardens, cottage gardens.
  • No serious pest or disease issues. Root rot may occur in poorly drained soils. Deer and rabbit resistant.
  • Propagate by seed. Easily grown from seed, starting indoors in late winter and transplanting outdoors after the danger of frost has passed. Alternatively, seeds can be sown in the garden after the last frost date.
  • Ageratum houstonianum species is native to Mexico and Central America. It is reported to be a weed and invasive outside its native range, due to its high production of small seeds with easy dispersal by wind or water. It is reported invasive in Australia and South Africa and neighboring countries (Swaziland, Mozambique and Zimbabwe) where it poses a threat to biodiversity.

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Requirements

Hardiness 2 - 11
Heat Zones 1 - 11
Climate Zones 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Plant Type Annuals
Plant Family Compositae
Genus Ageratum
Common names Floss Flower
Exposure Full Sun, Partial Sun
Season of Interest Spring (Late)
Summer (Early, Mid, Late)
Fall
Height 1' - 3'
(30cm - 90cm)
Spread 1' - 2'
(30cm - 60cm)
Spacing 12" (30cm)
Maintenance Low
Water Needs Average
Soil Type Chalk, Clay, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Moist but Well-Drained
Characteristics Cut Flowers, Plant of Merit, Showy
Tolerance Deer, Rabbit
Attracts Bees, Butterflies
Garden Uses Beds And Borders, Edging
Garden Styles City and Courtyard, Informal and Cottage
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Ageratum (Floss Flower)
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Alternative Plants to Consider

Ageratum houstonianum ‘Blue Mink’ (Floss Flower)
Ageratum houstonianum ‘Dondo White’ (Floss Flower)
Ageratum houstonianum ‘Red Bouquet’ (Floss Flower)
Ageratum houstonianum ‘White Bouquet’ (Floss Flower)
Ageratum houstonianum (Floss Flower)

Recommended Companion Plants

Dahlia ‘Mrs Eileen’
Antirrhinum majus (Snapdragon)
Agastache ‘Black Adder’ (Giant Hyssop)
Stipa tenuissima (Mexican Feather Grass)
Rudbeckia hirta ‘Prairie Sun’ (Black-Eyed Susan)
Verbena bonariensis (Tall Verbena)

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Ageratum (Floss Flower)
While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.
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Requirements

Hardiness 2 - 11
Heat Zones 1 - 11
Climate Zones 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24
Plant Type Annuals
Plant Family Compositae
Genus Ageratum
Common names Floss Flower
Exposure Full Sun, Partial Sun
Season of Interest Spring (Late)
Summer (Early, Mid, Late)
Fall
Height 1' - 3'
(30cm - 90cm)
Spread 1' - 2'
(30cm - 60cm)
Spacing 12" (30cm)
Maintenance Low
Water Needs Average
Soil Type Chalk, Clay, Loam, Sand
Soil pH Acid, Alkaline, Neutral
Soil Drainage Moist but Well-Drained
Characteristics Cut Flowers, Plant of Merit, Showy
Tolerance Deer, Rabbit
Attracts Bees, Butterflies
Garden Uses Beds And Borders, Edging
Garden Styles City and Courtyard, Informal and Cottage
How Many Plants
Do I Need?
Explore Great Plant Combination Ideas
Ageratum (Floss Flower)
Not sure which Ageratum (Floss Flower) to pick?
Compare Now

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