leelinms的部落格

• It's the aluminium in the petals that makes them blue

• Aluminium is only available to plants growing in acid soils

• To keep the flowers blue the hydrangeas require freely available aluminium so need either a naturally acid soil or regular watering with an acidifying solution

• A blue hydrangea will turn pink within one growing season if planted in a non-acid soil

• It may take many years to turn a pink one blue using the acid watering products available in garden centre

Tips for pruning some varieties of hydrangeas

The hydrangea your maiden aunt grows is probably a mophead H. macrophylla with old-fashioned, blowsy pompoms which famously turn bluer the more acid your soil: for those which stay stubbornly pink, try watering with iron or aluminium salts. But that's only one of dozens of species available, each more elegant than the last.

All are easy to grow, given dappled shade and a moisture-retentive soil (dig in lots of leafmould or composted bark when planting). Pruning causes some confusion but it's actually straightforward: just dead-head spent flowers in winter or early spring. The exceptions are the paniculatas and H. arborescens: for maximum flower power, prune hard each year.

Lacecaps: Among the most elegant of all hydrangea flowers, the exquisite flattened heads of lacecaps are made up of tiny button-like flowers surrounded by a ring of showy sterile florets. H. macrophylla 'Mariesii Perfecta' is one of the best blues in an acid soil.

Pruning: Lacecaps and mopheads are pruned in the same way. Remove faded flowers in early spring, cutting back to just above the first pair of strong buds. For established plants, remove a few of the oldest stems too to encourage new growth that will flower next year.

Paniculatas: The spectacular cone-shaped flowers of paniculata hydrangeas bubble up in late summer until autumn. The creamy flowers of H. paniculata 'Grandiflora' fade to dusty pink and dry on the plant.

Pruning: You can get away without pruning, but you'll get more flowers if you cut back hard each spring. Remove all stems to the lowest pair of healthy buds, creating a framework about 30-50cm above the ground.

Oakleafs: The gorgeous sculptural oak-shaped leaves of H. quercifolia turn burnished bronze in autumn after producing showy flowers similar to paniculata types.

Pruning: Dead-head flowers and remove dead and over-long stems in spring: otherwise no pruning required.

Serratas: Exquisitely dainty and small enough to grow in containers, H. serrata is widely grown in Japan but less well-known here. It has lacecap-like flowers and smaller leaves than its blowsier cousins.

Pruning: As for mopheads and lacecaps.

H. arborescens: The cultivar 'Annabelle'  has won many a garden designer's heart and is a regular at RHS flower shows, with her louche pompom flowers of creamy white.

Pruning: As for paniculatas.

H. villosa: For sheer impact, nothing beats the rugged H. aspera'Villosa Group'. You'll need plenty of space for its wonderfully textural roughened leaves and sumptuous blue-purple flowerheads ringed with petals of palest mauve.