Your Garden: Border Control

Sep 30 2007 Bill Chudziak

A Real Stunner...the Lovely Modern Hybrid Hydrangea Macrophylla Bela (Skyblue)

The communal mophead hydrangea is a familiar sight across gardens from mid summer until the first frost bites.

They form the backbone of many late summer borders and while they perform their function in an admirable manner, the genus contains many refined alternatives, less commonly seen but just as easy to grow.

Hydrangea Paniculata

This Impressive shrub produces lovely conical ivory panicles of sterile flowers which float above the 'real' flowers.

It prefers light shade and can form a 10ft (3m) spreading mass.

PINK DIAMOND AND LIMELIGHT

This large shrub was introduced from Asia during the late 19th century and subsequently many worthy cultivars have been raised.

Hydrangea paniculata Limelight, left, has massive flower heads which look like generous 99 cones of over-frozen pistachio ice cream. Pink hues suffuse the plant with the onset of cooler nights.

Hydrangea paniculata Pink Diamond, has a particularly graceful habit and is capable of forming an upright 6ft mound, with many heads of sparsely populated white flowers.

As with all white hydrangeas, they are not affected by soil pH, more air temperature and they display their discontent with rosy autumnal cheeks.

SKYBLUE AND KARDINAL RED

Hydrangea flowers are comprised of a sterile floret - things that look like petals - and a central cone of many wee fertile flowers.

Most hybrids became sterile as breeders tried to increase the number of florets they'd produce, in turn reducing the fertile flowers required for further breeding.

The early introductions of hydrangea macrophylla from Honshu in Japan, bear very little resemblance some of the more modern hybrids such as Hydrangea macrophylla Bela (Skyblue) and the gorgeous flowering Kardinal Red, left.

On soil pH6.5 hydrangea macrophylla sports a red and cream garb.

PRUNING AND CULTIVATION

Retain as much of the old wood by pruning lightly. Cut back to the first pair of strong buds at the tips of the stem. Heavy pruning is reserved for the base and you remove one in four of the oldest growths so young shoots come through.

Hydrangeas prefer light shade and a rich soil with a thick mulch to conserve moisture, similar conditions for rhododendrons. Cold winds can damage the emergent foliage.

The essential element for blue flowers is aluminium. Hydrangeas planted in acid soils (pH7 or lower) are blue, becoming more electric as the soil acidity rises. Neutral to alkaline soils with a higher pH produce red and pink flowers. Sulphur or aluminium sulphate (blueing powder) can be used to lower pH and lime to raise it. Hydrangeas look good intermingling with dahlias, tender salvias and perennial lobelia.

VILLOSA

Hydrangea villosa is regarded as one of the best handsome shrubs, with a lax open habit to 6ft (2m) tall by 10ft (3.5m) across.

Large leaves and chunky stems are thickly coated in creamy hairs and form an admirable backdrop for their generous flower heads, frequently attaining one foot (30cm) across.

Well-tended specimen plants form a 6ft hoary grey sphere which erupts during September with an explosion of felted purple lozenges.

HYDRANGEA PETIOLARIS

This relative of the mophead hydrangeas is a sprawler that can extend to 80ft and cling to its host through aerial roots. Plant towards the outside corners, leaving the centre for choicer species that can be tied in.

Flower heads arrive by the thousand and the small creamy bracts look like frozen confetti. One plant should cover six square feet in a few years and planted en masse the effect is quite grand.