Rhododendrons are hardy, evergreen plants that flower from late winter to early spring. They add drama and a pop of colour to your garden, and come in a range of varieties. Growing them is easy, this guide will show you how.
Rhododendrons are hardy, evergreen plants that flower from late winter to early spring. They add drama and a pop of colour to your garden, and come in a range of varieties. Growing them is easy, this guide will show you how.
It is commonly thought that Rhododendrons only grow in a cold climate, but tropical varieties are also available that prefer more temperate climates.
These are evergreen shrubs, which flower from late autumn to early spring. They have leathery leaves and are available in large and small flowered varieties. They can grow from 50cm up to 4 metres. There are over 100 varieties to choose from so see in-store for your preferred variety. It’s a good idea to buy them when they are in flower, that way you can see their colour.
Vireya (tropical) Rhododendrons have glossy leaves and flower for many months. They come in unusual colours like orange, salmon and red. Some tropical varieties are reasonably cold tolerant, but almost all of them dislike frost. Here are a few varieties to consider:
Best planted from March through to September.
Best planted from September through to March.
They prefer full sun in winter, and part shade in summer. These Rhododendrons grow best in cooler climates with deep soil and high rainfall. They have a very shallow root system so they can be easily grown in the garden.
Position in full sun to dense shade. Plants grown in shadier spots tend to be less compact than in full sun. Protection from the afternoon sun will help prevent leaves from sun damage.
Both Himalayan and tropical varieties grow best in a moist, well-drained lime-free acidic soil. Dig in plenty of compost and organic material before planting.
Rhododendrons must have plenty of water. Without enough in summer they will shut down their flower production for the following spring. However, they don’t like their feet to be sitting in water, so ensure that the soil is free draining.
These varieties require plenty of water when new growth appears after flowering has finished. Deep watering is more effective than light sprinkling. In the first few years make sure they don’t fry out in summer.
Water each shrub deeply through the drier months.
Use a Rhododendron specific fertiliser immediately after flowering.
Mulch sparingly over the roots and feed with a rhododendron specific fertiliser in spring after the first flush of flowers. Making sure the fertiliser is watered in immediately.
Mulch and feed to keep the roots moist in summer. This also helps suppress weeds and reduces watering need. Keep mulch away from the plant’s stem as this can lead to rot and pests.
| Problem | Symptoms | Remedy |
|---|---|---|
| Aphids | Clusters of small sucking insects that appear on new growth. | Spray with insecticide at two weekly intervals |
| Mites | Mites are minute sucking insects found on the underside of leaves in a fine webbing causing distortion, speckling and silvering of leaves to cause the leaves to go yellow (stippled or mottled) and dehydrated in hot dry weather. | Spray with mite killer |
| Thrips | Small black sucking insect that cause the leaves to go silver and dry. Brown-black specks on the underside of leaves. | Spray with insecticide at 2-3 weekly intervals through summer |
| Scale Insect | Scale Insects suck the plant sap and appear as small brown lumps on the stems and foliage. | Spray with insecticide at two weekly intervals. |
| 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 |
| Balling | Balling is when the flower bud starts to show colour but does not open and turns brown. | This is caused by frost, rain or sunburn. Move the plant to a more sheltered position. |
| 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. |
| 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. |
| Sun Burn | Leaves yellow and/or develop dark purple tone. Slow, stunted growth. | Move the plant to a more sheltered position, increase watering and mulch around the shrub. |
Rhododendrons can be pruned easily and very effectively. Prune young plants and old plants to create the shape you like.
When pruning, look for a growth bud on the stem that you are wanting to cut. Prune just above the bud and new growth will appear there. Look carefully on old wood to find growth buds.
Pruning is best done after flowering in late spring, this gives the plants the best possible chance of flowers for the following season. In heavy frost climates prune in summer/ autumn.
Pinch out leggy branches after flowering to encourage shrubs to bush out.
On the whole Rhododendrons are really hardy, so if something looks amiss use ageneral insecticide or fungicide, or come and see us in-store.
