Rhododendrons & Azaleas

Posted by on 18 November 2019

These plants form a branch of the ericaceae family and can 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: ie Maples, Dogwoods and Magnolias, Camellias, Pieris, Daphnes and 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. In this brochure we mainly list the better-known traditional Rhododendrons but even these vary tremendously in colour, foliage and form.

As a guide, the smaller the leaves the more sun they require, while the larger the leaves the more shade and shelter is appreciated. Any questions, please ask one of the team at Blue Mountain Nurseries- we’re here to help.

Miniature Rhododendrons

This is a name we have coined for a group of Rhododendrons that have small leaves, and often, many small flowers. It also encompasses most of the alpine Rhododendrons. Like the miniature roses these Rhododendrons cover all the height sizes, i.e. really dwarf to medium growers and even some up to 2m plus. Most of these mini Rhododendrons will stand the sun and are hardier in windy and frosty conditions.

Miniature rhododendrons do not like deep mulch or clay soils and they should be grown in a raised area. The soil should be raised with peat and bark as described below. As these plants are usually a year younger than their larger cousins they are priced from $15.00 - $25.00.

Planting and Soil Preparation

Rhododendrons must have some sun to flower well, especially the small-leaved varieties. Rhododendrons require constant moisture and prefer humidity, so that a site sheltered from drying winds, particularly from the north west, is crucial. Dappled shade, especially in the hot part of the day is preferred for the larger leaved varieties.

A well-drained soil is essential as Rhododendrons will not survive in boggy ground. The fine feeding roots are killed if the soil becomes saturated for even a day or so and although the plants may appear healthy for a considerable time, the first burst of hot weather will cause their collapse.

An ideal soil therefore is one which is light, porous and free-draining, yet able to retain sufficient moisture for the plant's needs. This can be achieved by the incorporation of peat moss liberally with the soil (one-part peat to two parts soil is not too much). In recent years we have found a mixture of 1/2 peat and 1/2 fine bark to be an ideal media to grow our Rhododendrons and Azaleas in. We now manufacture this especially for this purpose and sell both in bag lots and in bulk. In many areas, particularly in clay soils, where water does not drain away quickly, we strongly advise raising beds 15cm above the ground with this media. When planting is complete, finish with a mulch of pea straw- this will feed the plants and suppress the weeds.


Rhododendrons need a soil that is constantly moist and because they are shallow rooted, need frequent watering in hot dry weather. Providing that the drainage is good, it is difficult to overwater a Rhododendron. Mulching to keep the roots cool and moist is extremely beneficial. Loose material that allows air and water to penetrate, such as rotted sawdust or bark, are ideal. Never allow lawn clippings to become slimy and fresh animal manures can mean a quick death for any Rhododendron.


Rhododendrons do not need a rich soil. We recommend light application (i.e. a handful per average sized plant) of 2 parts blood and bone and 1-part superphosphate fertiliser, at the end of September and again in late January. DO NOT ADD FERTILISER TO THE SOIL WHEN PLANTING: peat/bark is all that is required.

Additional Points

1. Because Rhododendrons are surface rooting, avoid hoeing or cultivating close to the plant. A good mulch will suppress most weeds.

2. 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.

3. Rhododendrons are easily shifted as they have a fine root system which can be kept intact. This is best done in the Autumn or Winter, or when conditions are cool and moist.

4. After flowering the 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.

5. Most larger growing varieties may take several years to flower - do not despair if yours do not flower immediately. Good things take time!

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