BIG FRIENDLY GIANTS
Rhododendrons are majestic but there are smaller beauties too . . .
STrOLL through Britain’s greatest gardens this month and it’s easy to see why rhododendrons are popular. In May and June they’re at their glorious best, looking especially good in bold groups planted among taller trees. Gardens such as Trebah or Trewithen in Cornwall, the Savill Garden at Windsor, or Manderston in the Scottish Borders, have vast displays. You couldn’t aspire to that in a small garden — nor would you want to. The price of a few weeks’ glory would be ten months of evergreen foliage.
But, with more than 500 species and countless varieties in all shapes and sizes, there are rhodos for everyone.
The smallest are tiny shrublets, such as purply-blue-flowered
Rhododendron impeditum which grows 45cm high. At the other extreme, R. arboreum can become a 12m forest tree. Young plants are sold in containers and are available all year round.
But if you buy now, they’re likely to be in bud or bloom, ready to put on a show.
How well they grow depends on where you live. rhododendrons can only survive in acid conditions. Alkaline soils — such as those overlying chalk or limestone — are toxic to them. Most sulk, even in neutral soil.
If your garden has the wrong soil, try hydrangeas, shrub roses or lilacs instead. But don’t give up on rhodos — instead give them a go in containers.
CONTAINED JOY
COMPACT evergreen varieties, which you may know as azaleas, thrive in pots or half tubs in gentle sun or part-shade.
These containerised rhodendrons live happily for years. They grow slowly but flower every spring for several weeks, and need little attention, other than a fortnightly feed between now and August.
Eight years ago I potted up rhododendron Kirin. This week — as every May — the leaves are hidden by masses of pink flowers. Despite being in the same large pot, the plant is still fine and has grown barely a metre.
Be sure to choose hardy varieties. Evergreen azaleas are also sold as house plants but are another species — Rhododendron
simsii — and non-hardy. You can grow large-leaved rhododendrons in containers, too — but choose dwarf kinds.
Among the best are Yakushimanum varieties such as Golden Torch, pink Bashful or red Dopey.
There are two ways to check whether your soil is rhodofriendly. For accuracy, buy a pH-testing kit. rhodos prefer soils at pH 5.5 or below.
The easiest way is to peep into neighbouring gardens. If there are healthy rhododendrons or camellias in view, your soil is probably fine too. But, if you know your ground to be alkaline, containers are best.
CARE FOR AZALEAS
RHODODENDRONS are shallow rooted and susceptible to drought damage. Adding compost or organic matter to soil will improve moisture retention — especially on sandy soils.
Small azaleas often develop as low mounds, rather than upright shrubs. They look pretty in wide, shallow-sided containers, such as half barrels or troughs.
Given time, each plant should spread beyond the container sides, curving towards the ground. As that happens, snip off any shoots that stick out.
Always use top quality ericaceous potting compost. Make sure each container drains freely and put broken crockery in the bottom to prevent drainage holes from clogging up. Eventually, potted azaleas grow old and feeble — but with well-managed plants, that may take a decade.