Ageratum cultivation techniques

Height: 15-60cm (6-24in)

Planting distance 23-30cm (9-12in)

Features: flowers summer until first frost

Soil: ordinary, moisture-retentive

Site: sheltered sunny or lightly shaded

Type: half-hardy annual

An abundance of delicate, powder-puff flowers and a long season -from early summer until the first severe frost – make Ageratum a popular bedding plant. The low, compact varieties 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 look stunning in flower arrangements, associating well with many garden species.

The original blue-flowered species, Ageratum houstonianum, has largely been replaced by garden varieties.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 flowerheads, but you do pay a little more for them.

Popular varieties:

‘Adriatic’, an F1 hybrid, has a neat compact habit, reaching 15-20cm (6-8in), and mid-blue flowers.

‘Blue Bouquet’ reaches 45cm (1 8 in) high, with blue flowers.

‘Blue Champion’, a vigorous but compact II 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 F1 variety, growing up to 30-45cm (12-1 Bin), with purple-blue flowers. It is ideal for the middle of a border or for cutting.

‘Blue Mink’ is a vigorous yet compact plant reaching 23-3()cm (9-12in) high with powder blue flowers.

‘Blue Ribbon’, an F1 hybrid, is smothered in bright mid-blue flowers from early summer. It grows 15-20cm (6-8in)high.

‘Blue Swords’ forms a sturdy and bushy plant, 20cm (8 in) tall. It bears dense clusters of mid-blue flowers. Good weather resistance.

‘Capri’ bears rich deep blue flowers on compact plants and grows 20-30cm (S-12in) high.

‘Highness’ is another tall F1 hybrid, growing up to 60cm (24in) 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 flowers.

‘Pacific’, an F1 hybrid, is free flowering, with purple buds opening deep violet blue. It grows 20cm (8in) high.

‘Pink Powderpuffs’ is a compact grower, up to 15cm (6in) high, with blush pink blooms. “Pinky Improved’ Forms bushy mounds 15-23em (6-9in) high and has dusky pink flowers.

‘Southern Cross’ grows 20-30cm (8-12in) high and is suitable for bedding, containers and 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 flowerhcads.

‘Swing Mixed’, an F1 hybrid, growing 15-20cm (6-8in) high, is a mixture of soft colours.

‘White Blue Capri’ has unusual blooms with blue petals and white centres, and grows up to 30cm (12in) high.

‘White Hawaii’, an F1 hybrid, is a vigorous, uniform white variety, 15cm (6in) high.

Cultivation

Sow under glass in early spring. Harden off in a frame, then plant out young plants or bought bedding 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.

Pests and diseases: Foot and root rot sometimes cause the plants to collapse.

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