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A guide to rhododendrons

Rhododendrons are a hardy plant that thrives in moist soil. Here’s some expert guidance you can pass onto your clients on how to properly care for them, thanks to Rebecca Hughes from Blue Mountain Nurseries

Rhododendrons and azaleas form a branch of the ericaceae family and offer a wide variety of plant sizes, flower colours, foliage types and plant forms, as well as lending themselves to interesting groupings. They associate well with other plants that enjoy similar conditions, such as maples, dogwoods and magnolias, camellias, pieris, daphnes, small woodland bulbs and perennials.

Rhododendrons come in many shapes and forms. Some small growers are mountain plants and make great plants for growing in the alpine garden, while others make attractive house plants.

As a guide, the smaller the leaves the more sun they require. Plants with larger leaves require more shade and shelter.

Rhododendron care tips to share with your client:


Rhododendrons need soil that is constantly moist and because they are shallow rooted and require frequent watering in hot dry weather. Providing the drainage is good, it is difficult to overwater a rhododendron. Mulching to keep the roots cool and moist is extremely beneficial, while loose material that allows air and water to penetrate, such as rotted sawdust or bark, is ideal.

Lawn clippings that have become slimy and fresh animal manures can mean a quick death for any rhododendron, so avoid using these when you plant them in your client’s gardens!


Rhododendrons do not need a rich soil. A light application (for example, a handful per average sized plant) of two parts blood and bone, and one-part superphosphate fertiliser, at the end of September and again in late January is recommended.

Additional points

Rhododendrons are surface rooting, so avoid hoeing or cultivating close to the plant. Instead, use a good mulch as

this will suppress most weeds.

  1. Dry brown edges on tops of the leaves are a sign of drying, normally caused by excessive wind and sun. This can only be remedied by providing additional shelter or shifting the plant to a more sheltered spot. Too much fertiliser may also cause this problem.

  2. Rhododendrons can be moved easily as they have a fine root system which can be kept intact. This is best done when conditions are cool and moist, such as autumn or winter.

  3. After flowering, old flower heads should be gently twisted off, as this promotes improved flowering the following year. Young plants should be pinch pruned if they are not naturally bushy varieties. This is done just after flowering or when the new shoots appear.

  4. Most larger growing varieties may take several years to flower - good things take time!

Rhodo Selection Guide
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Rebecca Hughes has an honours degree in Botany and a background in education as National Training Manager for the Horticulture Industry Training Organization (ITO) and General Manager for the Community Support Services ITO.

She currently works with Blue Mountain Nurseries, a family-run wholesale and retail plant nursery based in Tapanui with a passion for plants since 1932.


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