Ageratum floss flower
Height 12-30cm (5-12in)
Planting distance for dwarf varieties 23cm (9in); for taller varieties 30cm (12in)
Flowers early summer till first severe frost
Any moisture retentive
Sheltered sunny or lightly shaded site
Their abundance of, and their long season – from early summer until the first severe frost – make Ageratum a popular bedding plant. Its low, compact habit and powder-puff flowers look most effective edging formal beds, filling gaps in borders of low-growing plants or brightening up window boxes and containers. Some of the taller varieties are useful for flower arranging, associating well with many other garden plants.
The original blue-flowered species, Ageratum houstonianum, has largely been replaced by garden varieties. These come in blue, pink, mauve and white.
The F1 hybrids – first generation plants obtained by crossing two varieties known for their ability to produce consistently similar offspring – are particularly vigorous and have the largest flower heads, but you do pay a little more for the seeds.
Popular varieties ‘Adriatic’, an F1 hybrid, has a neat compact habit, reaching 15-20cm (6-8in), and mid-blue flowers. ‘Blue Bouquet’ is a giant, reaching 45cm (18in) high, with lavender-blue flowers, good for cutting. ‘Blue Champion’, a vigorous but compact F1 hybrid, has dark green leaves and large clusters of mid-blue flowers. It grows 15cm (6in) high. ‘Blue Danube’ reaches 15-20cm (6-8in) high and has lavender-blue blooms. It is one of the best early-flowering F1 varieties. ‘Blue Horizon’ is a tall-growing F1 hybrid, to 60cm (2ft) and good for cutting. Small purple-blue flowers are borne in clusters. ‘Blue Mink’ is a compact plant reaching 23-30cm (9-12in) high with powder-blue flowers. ‘Blue Ribbon’, an F1 hybrid, is smothered in bright mid-blue flowers from early summer on. It grows 15-20cm (6-8in) high. ‘Blue Swords’ forms a sturdy and bushy plant, 20cm (8in) tall. It bears dense clusters of mid-blue flowers. Good weather resistance. ‘Capri’ bears rich deep blue flowers on compact plants, 20-30cm (8-12in) high. ‘Highness’ is another tall F1 hybrid, growing up to 60cm (2ft) high. It has clusters of white to pale pink flowers on long stems. ‘North Sea’, an F1 hybrid reaching 15-20cm (6-8in) high, has deep blue or red flowers that continue until late autumn. ‘Pacific’, an F1 hybrid, grows 20cm (8in) high and forms a tight dome of deep mauve flowers on fast-growing plants. ‘Pinky Improved Selection’ is a new hybrid variety of bushy plants, 15-20cm (6-8in) tall. The flowers are dusty pink. ‘Southern Cross’ grows 20-30cm (8-12in) high and is suitable for bedding, containers and as cut flowers. The flower clusters are bi-coloured in pale blue and white. ‘Summer Snow’ is an F1 hybrid, 15-20cm (6-8in) tall, with pure white, fluffy flower heads. ‘Swing Mixed’ is an F1 hybrid mixture, with flowers in soft shades of blue, purple, rose and pink. The plants grow to 20cm (8in) high.
Sow under glass in early spring. Harden off in a cold frame, then plant out seedlings or bought bed-ding strips in late spring to early summer, setting the dwarf varieties 23cm (9in) apart, and the taller varieties 30cm (12in) apart. They need a sheltered sunny site and moisture retentive soil. Deadhead regularly to prolong the flowering season.
Pests and diseases
Foot andsometimes cause the plants to collapse.