Azaleas and Rhododendrons
Azaleas and Rhododendrons are the most decorative evergreen shrubs, popular for their vivid displays of flowers from late winter to early summer.
Azalea and Rhododendron flowers come in many forms from tubular, starry, bell and bowl shaped, large and small, and even fragrant.
At a Glance:
- Height - 50cm to 4 metres
- Position - semi shade
- Soil - moist, lime free, well drained
- Flower - late winter to summer
- Colour - pink, white, red, yellow, cream, mauve, blue, purple, orange.
Rhododendrons (pictured above) are evergreen and flower from late winter to early summer.
There are large and small flowered varieties. They grow from a height of 50cm to 4 metres. Modern varieties tend to reach only 2 metres.
Azalea indica (pictured below - left) is the best known evergreen azalea. Flowers from late winter to early summer, in coastal regions to cooler highlands. They have large flowers, small leaves and grow from 60cm to 1.2 metres in height.
Kurume azaleas (pictured below - centre) are evergreen with small leaves and small single or semi double flowers which smother the plant in spring. Kurume azaleas tolerate cooler temperatures and require less shade than indica varieties. Grow from 60cm to 1 metre in height.
Mollis azaleas (pictured below - right) are deciduous, losing their leaves in winter. Flowers appear before the foliage in spring. Some varieties are fragrant. Foliage is highly coloured in autumn. Prefers a cooler climate. Will grow in full sun to a height of 1.5 metres
When to Plant
The best time to plant is from winter to early spring, before flowering. Azaleas and rhododendrons can be planted at any time as long as they are well watered through the summer months.
Where to Plant
Plant in a moist well drained soil that has plenty of good compost (make sure the compost has no added lime in it) and organic material, dug in before planting. Raise beds in clay soil to improve drainage.
Plant in shade to filtered sunlight. Some varieties will tolerate sun.
Azaleas look great in mass plantings, mixed borders with other plants, in front of a background of evergreen shrubs or under deciduous trees.
Rhododendrons are at their best planted in mixed borders, blending in well with many other plants
How to Plant
Before planting water the plant well. Dig in plenty of good compost (make sure the compost has no added lime in it) , well rotted animal manure or organic material to the planting hole.
After Care …
Rhododendrons and azaleas do not require a lot of fertiliser.
Apply sparingly as they have very shallow surface roots which can burn easily.
Rhododendrons and Azaleas are acid lovers - i.e. they HATE LIME! So we recommend you apply Tui Acid Fertiliser in late winter and again in mid summer.
Regular watering through summer is required. Deep watering is more effective than light sprinklings.
This is essential for success!
Apply a 5cm thick layer of good compost (make sure the compost has no added lime in it) or mulch around azaleas and rhododendrons in late winter and again in mid summer to ensure roots stay cool and moist.
Regular pruning is not required. However, sometimes they will benefit from being cut back.
A spindly young rhododendron can be cut back by one third of its length, above a bud, in late winter early spring. Pinch young shoot tips to encourage bushy growth.
Pests and Diseases
Thrips are small black sucking insects that cause speckled silvery leaves. Spray with Mavrik or Confidor.
Mites are minute sucking insects found on the underside of leaves that cause distortion, speckling and silvering of leaves. Spray with Mavrik.
Aphids are small sucking insects on new growth. Control with Confidor.
Leaf Roller Caterpillars chew holes in leafs and flowers and roll themselves up in the leaves with webbing. Squash the caterpillar with fingers, or spray with Mavrik.
Powdery Mildew makes the leaves generally appear smaller, off-colour and the underside of the leaves are covered in a powdery like substance. Try to improve air circulation around the plant. Spray with Yates Fungus Fighter.
Alkaline Soil - If the soil is too alkaline yellow patches appear between the veins. Use Tui Acid Fertiliser to correct this.