Rhododendrons

Enjoy beautiful flowers and year-round garden interest with the right planting position and a little care. The essentials are shelter, free-draining soil and reliable moisture.

At a glance: Choose a sheltered position, prepare a free-draining bed, keep the roots moist and feed lightly. Avoid waterlogged ground and do not add fertiliser to the planting hole.

Choosing your plants

Rhododendrons and azaleas belong to the Ericaceae family and offer a wonderful range of flower colours, foliage, sizes and growth habits. They combine well with maples, dogwoods, magnolias, camellias, pieris, daphnes, woodland bulbs and perennials that enjoy similar conditions.

Small-leaved and miniature rhododendrons

Our miniature rhododendron group includes small-leaved varieties, often with masses of small flowers, and many alpine types. “Miniature” describes the foliage and flowers rather than the eventual plant size: some remain very dwarf, while others can reach 2 metres or more.

Many of these varieties tolerate more sun, wind and frost than larger-leaved types. Avoid deep mulch around them and use a raised planting area where clay soils drain poorly.

Choose a sheltered position

Rhododendrons need some sunlight to flower well. As a general guide, small-leaved varieties tolerate more sun, while larger-leaved varieties appreciate dappled shade, especially during the hottest part of the day.

Shelter from drying winds is particularly important. Avoid exposed positions that catch strong north-westerly winds, and choose a spot where you can maintain even soil moisture through summer.

Prepare the soil before planting

Good drainage is essential. Rhododendrons have fine feeding roots that can be damaged by saturated soil. A plant may appear healthy for a time after waterlogging, then collapse when hot weather arrives.

Aim for a light, porous soil that drains freely while holding enough moisture for the roots.

• Improve the planting area: Incorporate peat moss generously into the soil. The original nursery recommendation is one part peat to two parts soil.
• Use a suitable growing medium: At Blue Mountain Nurseries, we have found a mixture of equal parts peat and fine bark effective for growing rhododendrons and azaleas.
• Raise beds on poorly drained ground: In clay soils, raise the planting area approximately 15 cm above the surrounding ground using this mixture. Make sure excess water can drain away.

Do not mix fertiliser into the soil when planting. Focus on preparing the soil and providing suitable drainage.

Water regularly and mulch carefully

Rhododendrons are shallow rooted and need frequent checks during hot, dry weather. Keep the root area consistently moist, while ensuring excess water drains away.

A loose mulch of bark or well-rotted sawdust helps keep the roots cool, retains moisture and suppresses weeds. Use material that allows air and water to pass through, and avoid a deep layer around miniature varieties.

Avoid fresh animal manure and do not allow lawn clippings to build up into a wet, slimy layer.

Feed lightly

Rhododendrons do not need rich soil or heavy feeding. Our traditional recommendation is a light application of two parts blood and bone to one part superphosphate at the end of September, followed by another light application in late January.

Take care with quantities: too much fertiliser can damage the roots and scorch the leaves. Do not add fertiliser to the planting hole.

Caring for established plants

Protect the shallow roots

Avoid hoeing or cultivating close to the plant. Mulch helps control weeds without disturbing the fine surface roots.

Remove spent flowers and encourage bushy growth

After flowering, gently twist off the old flower heads, taking care around the new growth. Young plants that are not naturally bushy can be lightly pinch pruned just after flowering or as new shoots appear.

Watch for brown leaf edges

Dry, brown leaf edges can indicate stress from drying winds, strong sun or excessive fertiliser. Check moisture levels and feeding history, and consider extra shelter or a more suitable position.

Move plants in cool conditions

Rhododendrons can often be moved successfully because their fine root systems can be kept intact. Autumn or winter is best, or another period when conditions are cool and moist.

Allow time for flowering

Some larger-growing varieties take several years to flower. Give young plants time to establish and develop.

Need help choosing a rhododendron? Talk to the team at Blue Mountain Nurseries about varieties suited to your garden and growing conditions.

Compare varieties by flower colour, listed size and flowering month to help choose rhododendrons for your garden.

This selection guide is a reference guide rather than a current stock list. Please check availability with Blue Mountain Nurseries. Sizes are at 10 years under average growing conditions.  Flowering times may vary with location and season.

Open a colour below to compare varieties.

Ask us about availability and choosing a variety