Pick a Plant – Hydrangea

One of the most frequent groups of plants we are asked about is the Hydrangea family. The main ones grown and sold in this country are the Hortensias (the familiar mop-headed hydrangeas) and the Lacecaps which are a smaller group, producing flatter, large heads of fertile flowers around which are borne a ring of coloured ray florets.

Other species include the paniculate types, native to Japan, China and Formosa, with their enormous pyramid shaped flowers, usually white with a touch of pink, the Serrata species, which are much dwarfer, with two-tone flowers in blue and white, often turning rosy crimson, and native to Japan and Korea.

All are easily grown but need generous treatment. Those classic scholars amongst you will know that the word Hydra is from the Greek, meaning water, and all hydrangeas resent dryness at their roots. When planting, add a generous amount of well rotted manure or compost to aid water retention and add mulches in summer to avoid drying out.

The larger leaved specimens will require some shade in summer to avoid drying out, although they need high light levels as well. They do not like cold, drying winds so those in East Lothian and the lower parts of West Lothian need to protect hydrangeas from east winds.

Get it right and hydrangeas will provide a garden with weeks of glorious, wax-like flowers to brighten up a shrub border, or as an eye-catching specimen in a corner or in a stylish container.

Many varieties also have autumn coloured foliage. Flower colour is affected by the availability of iron. Acid soils with a PH below 5.5 produce blue flowers, while soils with a PH greater than this tend to produce pink flowers. This is why they can change colour over a number of years. For a bit of fun, you can alter the colour by adding lime to make the soil alkaline or iron to make it acidic.

Pruning consists mainly of thinning it and cutting back old flowering shoots to within a few centimetres of the old wood, immediately after flowering. In colder areas, such as the top half of West Lothian, this is better left until early spring.

For container grown plants, use a John Innes Number 3 compost with added farm yard manure to prevent drying out.

Hortensia varieties worth planting include Hydrangea involcucrata Blue Prince, (pictured) King George (pink) La France (pale pink to mid blue) Miss Belgium (rosy red) Queen Elizabeth (pink). All are suitable for seaside planting.

Lacecap or mophead varieties (Macrophylla) to consider include Altona (fiery red with pale cream centres) Ayesha (deep pink) Blue Bonnet, Hamburg (pink) Generale Vicomtesse de Vibraye (pink) pictured left.

Grandiflora is one of the showiest with white panicles fading to pink. They make excellent cut and dried flower decorations. Kyushi Erect has glossy green leaves and large cones of pure white flowers. Pink Diamond is also striking.

Petiolaris is the climbing hydrangea. This is a strong growing, self clinging species which can climb 10-15 metres high on north facing walls or trees. It has dull, greenish white flowers which emerge over a long period from June to August.

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