Boring garden? Let rhododendrons ride to the rescue. Rhododendrons are a spectacular flowering plant that add a bit of drama and a pop of colour to your garden. Most people associate the name with a cold climate "mountain loving" plant, but more tropical varieties are also available that prefer more temperate climates.
Great news for us, is that there is a rhododendron variety that will suit almost any part of New Zealand.
Rhododendron varieties
Himalayan (cold climate) Rhododendrons
Himalayan (Cold climate) Rhododendrons have leathery leaves and massed flower display in spring, the flowers (generally pink or white) almost cover the evergreen leaves. Himalayan varieties were taken to Europe, and many people mistakenly think they are native to England because they thrive in the English climate.
Planting and maintenance
These Rhododendrons grow best in cooler climates with deep soil and high rainfall. Use a Rhododendron specific fertiliser immediately after flowering.
Vireya (tropical climate) Rhododendrons
Vireya (tropical) Rhododendrons have glossy leaves and flower for many months (but more sparsely), and come in unusual colours (orange, salmon and red). They are native to Indonesia, Malaysia, New Guinea, and Australia.
Planting and maintenance
Vireya's tropical origins mean that they can be grown in many parts of New Zealand. These varieties need excellent drainage - they can survive on the moisture that collects in leaf litter around their roots. They prefer mottled shade with a few hours of morning sun.
Mulch sparingly over the roots and feed with a rhododendron specific fertiliser in spring after the first flush of flowers (make sure it’s watered in immediately). Some tropical varieties are reasonably cold tolerant, but almost all of them dislike frost.
Planting Rhododendrons - general
All rhododendrons grow best in acidic, nutrient rich soil. Dig plenty of well broken down compost material into the bed before planting.
Some varieties grow into large trees so check that your planting position allows room for growth.
Smaller varieties grow well in pots. Use a good quality potting mix and a generous sized pot.
Prune (if necessary) immediately after the flowering period.
Rhododendron troubleshooting
Below is a quick guide to the pests and diseases that rhododendrons can be prone to:
Problem
Symptoms
Remedy
Aphids
Clusters of insects on young growth.
Spray with insecticide at two weekly intervals
Mites
Leaves yellow (stippled or mottled) and dehydrated in hot dry weather.
Spray with mite killer
Thrips
Leaves silver and dry. Brown-black specks on the underside of leaves.
Spray with insecticide at 2-3 weekly intervals through summer
Sooty Mould
Black sooty mould on leaves and twigs.
Spray with fungicide
Petal Blight
Early symptom - light brown or whitish coloured circular spots on petals. Advanced symptoms - Petals feel slimy. Spots enlarge to form irregular blotches until whole flower collapses. Diseased flowers dry up and cling to the plant (leaves and stems are not affected).
Avoid overhead watering. Pick off diseased flowers. Spray at two weekly intervals fungicide
Lack of Fertiliser
Leaves yellow and/or develop dark purple tone. Slow, stunted growth.
Rhododendron specific fertiliser in late spring after flower finishes and just before new growth starts
Soil too Alkaline
Decline in vigour and leaves turn yellow while the veins remain green
Rhododendron specific fertiliser in late spring after flower finishes and just before new growth starts. Do not use lime.
