Species: Ageratum houstonianum (synonym A. mexicanum)
Family: Asteraceae (Compositae)
Common name: Floss Flower
Grow as: annual
Height: 10cm60cm (4 to 24 inches)
Flowering period: June to October
Ageratum is popular in gardens and is typically used as a low-growing bedding plant for containers and displays.
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The original species Ageratum houstonianum is a native of Mexico, where it grows as a perennial semi-shrub up to 60cm (24 inches) high. The leaves are toothed, heart-shaped to ovate, vivid green, covered with a light down.
The densely clustered cymes are made up of flower heads of white, pink or generally blue tube-shaped florets. In full bloom the flowers can completely cover the leaves. Only a few varieties attain a height of 60cm (2 feet) and are used for cutting. Most varieties are low growing, 1020cm (4 to 8 inches). All bear a profusion of flowers.
Ageratum does best in well-drained soil in a warm and sunny situation. If watered sufficiently in the flower bed and provided with fertiliser the plants will be a decorative feature in the garden for the whole summer.
Ageratum has many uses. Taller varieties are planted in borders and for cutting. Low-growing varieties are useful as an edging plant and are often used as bedding plants in parks. They are also grown in flower pots, boxes on balconies and containers for the decoration of gardens and the public areas in towns.
Growing: the seeds should be sown from March until mid April at 2528°C (7882°F). The seedlings should be pricked out into trays and later into small pots or else thinly spaced in a frame. Growing on temperature should be 1520°C (6068°F).
The growing points should be pinched out once or twice so that they make good lateral shoots. The hardened-off seedlings should be planted out in the second half of May (they are sensitive to frost), spaced 1525cm (610 inches) apart. The flowers appear shortly after and the flowering period lasts until autumn. Water sparingly before planting outexcess water will promote lush growth and delay flowering.