Rhododendrons and Action Plan,
Rhododendrons are about to burst into life with a riot of colour...
THEY always strike me as having identity issues. Sombre and leathery-leaved, rhododendrons are stolidly masculine for most of the year. But each spring they erupt into outrageous colour and sashay in the breeze like drag queens.
Large varieties look magnificent when grown in quantity. You’ll find superb displays in historic gardens such as Caerhays or Trewithen in Cornwall, or Yorkshire’s Castle Howard. For more locations, try
greatbritishgardens.co.uk and search for ‘rhododendrons’.
Huge varieties flourish in such gardens. And if you like what you see, young rhodos are usually containerised and can be planted any time.
But don’t buy in haste. Large varieties can be fast-growing and many resent pruning. And lovely though they are in bloom, big rhododendrons can be boring — or downright ugly — for 11 months of the year.
Luckily, this is a diverse family with varieties in all sizes. The smallest are knee-high; the tallest, Rhododendron arboreum, grows to 12m.
Colours vary widely, from blue and purple through pink, crimson or scarlet to orange and yellow. Habits vary, too, and a few — such as R. bureavii have attractive foliage.
ACID TEST
RHODODENDRONS are picky about where they grow. The soil must be acid. If lime or chalk is present — even in tiny traces — they’ll die.
So if your natural soil is neutral or alkaline, they must be in containers or raised beds filled with ericaceous compost. If you’re not sure whether your soil is suitable, it’s easy to find out. The surest way is to test it with a pH meter — instructions come with the kit.
A crude but fairly reliable method is to see what grows in neighbouring gardens. If there are camellias or rhododendrons about, you’re in business.
Dwarf rhodos are perfect for container culture using ericaceous compost. Azaleas are also rhododendrons — despite the confusing name — and most make superb container plants.
The most suitable are evergreens with neat little leaves and dense, twiggy growth. A potted one has grown outside my front door for nine years and is still less than a metre across.
FLOWER POWER
COMPACT varieties include Kurume azaleas such as white
R. Adonis or pink R. Kirin — the one by my front door.
Reddish pink Amoena is a eliable beauty, too.
Dwarf azaleas are easy to prune — best done straight after flowering. But they’re naturally compact and get by with minimal snipping.
There are also compact rhodos with larger leaves and big flowers. The most popular, developed from R. yakushimanum, are known as ‘Yaks’. These are spectacular in bloom and quietly attractive for the rest of the year.
Other compact varieties with big flowers include smouldering crimson Vulcan and Dwarf Wren, whose primrose-yellow flowers have subtle beauty.
Rhododendrons and azaleas in the ground are easy to manage. Most are shallow-rooted and dislike drought, so use mulches to conserve soil moisture.
Constant use of mains water may reduce acidity, so use rain water when you can. Feed fortnightly from now to midsummer. I top-dress my pots with yellow sulphur each year, too. It helps to sustain acidity.