Royal azalea

Royal azalea: how do you recognise it?

Habit

Open, deciduous shrub about 2 m tall and wide; fairly slow growing.

Foliage

Obovate, 5–10 cm; five leaves sit together in a whorl at the shoot tips. Autumn colour orange to red.

Flower

Very large, 6–9 cm, pale pink with small red spots on the upper lobe, in April–May, often before or as the leaves emerge.

Fruit

A small, hairy capsule that splits open in autumn.

Roots

Shallow and finely branched: they dry out quickly and must not be disturbed by digging or hoeing.

Flowering: April–May · Plants: March–April and September–October · Pruning: May–June

Why grow it?

• Large, pale pink flowers in April–May, one of the most elegant azaleas for half shade.
• Lovely autumn colour: orange to red foliage.
• Fully hardy, to about −30 °C, and deciduous.
• Tolerates slightly less acid soil than most azaleas.
• The flowers are visited by bees and bumblebees; it needs little pruning.

Royal azalea: where does it grow best?

• Half shade is ideal; the flowers last longer there.
• Acid to nearly neutral soil (pH about 5–6.5): sand or loam rich in humus. Do not lime.
• Evenly moist but well drained; it dislikes both wet feet and drying out.
• Sheltered from cold east wind and from morning sun after a night frost, because it flowers early. Allow 1.5–2 m of space.

Light

Partial shade

Soil type

Sand, loam or peat

Acidity

Acid or neutral

Moisture

Normal

Size

2 m tall, 2 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Japanese maple: Fine leaves and good autumn colour next to the azalea.
• Bluebell: Blue flowers in April–May in half shade, at the same time as the azalea.
• Ferns: Fresh green foliage in the same moist, humus-rich soil.
• Hosta: Large leaves that fill the gap once the azalea has finished flowering.

Royal azalea: when and how to plant it?

Plant in March–April and September–October.

1. Plant in March–April or September–October, when the soil is neither frozen nor waterlogged.
2. Dig a hole 2–3 times as wide as the root ball, but no deeper. Mix the excavated soil with leaf mould or peat-free ericaceous compost.
3. Soak the root ball in a bucket of water until no more air bubbles rise, then gently tease out the roots.
4. Set the root ball so its top is level with, or slightly above, the soil: never plant deeper than in the pot.
5. Firm the soil and water straight away, preferably with rainwater.
6. Spread a 5–8 cm layer of leaf mould or pine-needle mulch around the base.

Care

Water

In dry weather give a good watering every week, preferably rainwater: tap water often contains lime. It is a little less sensitive to lime than other azaleas, but still does best in soft, more acid soil.

Feeding

In April–May, an ericaceous fertiliser or organic fertiliser. Not after July.

Mulching

Renew the leaf mould or needle mulch every spring. Do not dig or hoe around the shrub: the roots lie just below the surface.

Spent flowers

You may snap off spent flowers by hand without damaging the young buds below. It is not essential.

Frost protection

When a night frost is forecast in April, drape a sheet or fleece over the flowering shrub and take it off again during the day.

Tip: Choose a sheltered spot without morning sun and cover the shrub on frosty nights in April: the large flowers are sensitive to frost.

Royal azalea: when to prune it?

Pruning months: May–June.

When: It needs little pruning. Do it just after flowering, in May–June, because next year’s flower buds form in summer.

How:

• Snap or cut off spent flowers if you wish.
• Remove dead, weak and crossing branches at the base.
• Shorten overlong branches just above a side shoot to adjust the shape.
• An old, bare shrub can be cut back to 30–50 cm above the ground in March: it usually regrows, but will not flower that year.

Caution: Do not prune in late summer or autumn: you would cut off next year’s flower buds.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Layering

In spring, bend a low, flexible branch down, peg it into acid, loose soil and put a stone on top. Separate it with its roots after one or two years.

Seed

Scatter the fine seed in January–March on moist acid seed compost without covering it, in the light at 15–20 °C. Seedlings grow slowly and flower only after several years.

Royal azalea: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Flanders.
• A layer of leaves or needle mulch around the base protects the shallow roots, especially on young plants.
• The flower buds are sensitive to late night frosts in April; choose a sheltered spot or cover the flowering shrub when frost is forecast.
• In a pot the roots freeze more easily: stand the pot against a wall, wrap it in hessian and water on frost-free days.

Diseases and pests

• Frost damage to flowers: Brown, limp flowers after a night frost in April. Plant in shelter, not where it gets morning sun, and cover the shrub when frost is forecast.
• Chlorosis: Yellow leaves with green veins on soil that is too chalky. Acidify the soil with needle mulch and leaf mould, water with rainwater and give an ericaceous fertiliser.
• Powdery mildew: A white, powdery coating on the leaves, mainly in late summer in dry weather. Water at the base, leave space between plants and remove affected leaves.
• Vine weevil: Half-moon notches in the leaf edges in summer; the grubs eat the roots. Apply nematodes in August–September to warm, moist soil.

Through the year

• March: Plant. Ericaceous fertiliser. Renovate old shrubs if needed (no flowers that year).
• April: Flowering. Cover on frosty nights. Top up the mulch.
• May: Flowering and leaf emergence. After flowering, remove spent flowers.
• June: Prune lightly after flowering. Water with rainwater in dry weather.
• July: Water in dry weather. Watch for notched leaf edges.
• August: Water in dry weather. Apply nematodes against vine weevil grubs.
• September: Plant. Collect seed when the capsules open.
• October: Plant. Orange to red autumn colour. Top up the mulch.
• November: Rest. Fallen leaves can stay as mulch.

Edible and useful

Not edible. Rhododendrons and azaleas are poisonous in all their parts, including the flowers and nectar: they contain grayanotoxins, which cause drooling, vomiting, weakness, a slow heartbeat and low blood pressure. Goats, sheep and alpacas above all, but also horses, cattle, rabbits and guinea pigs become seriously ill from them, sometimes after only a small quantity of leaves; dogs and cats are at risk too. So never throw clippings over the fence of a field or into a pen or hutch, do not give them to animals, and do not pick greens for rabbits among the shrubs; if in doubt, call your vet at once. In children who put a leaf or flower in their mouth or suck nectar from the flowers, as they do with dead-nettle, it usually goes no further than a burning mouth and nausea, but teach them not to do it. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The species is named after Baron Alexander von Schlippenbach, a Russian naval officer who collected the plant in Korea in the 19th century.
• At the shoot tips five leaves usually sit together in a whorl: an easy feature to recognise.
• In the wild it grows in mountain woods and on rocky slopes.