Rhododendron maddenii

(MADDENIA H4) Large tubular funnel shaped white scented flowers suffused with rose or pale pink, with or without a darker blotch, in May and June. Broad shiny dark green foliage, densely scaley on the undersides. Stems and branches are smooth, with brown flaking bark. Height 75-100cm in 10 years.

A plant for very sheltered gardens, or cool conservatories. Needs well drained compost. Hard prune after flowering to keep plant in shape.

The lithograph is by Walter Hood Fitch. It is based on a sketch by Joseph Dalton Hooker whilst in the Himalayas and published in his landmark book, 'Rhododendrons of the Sikkim-Himalaya' (1849-1851)

Epithet: Named after Lt-Col E Madden (d. 1856), traveller in India.

• Recommended for the cool greenhouse or conservatory, and its lovely scented flower.
• Ideal position: sheltered position in the garden or in a cool conservatory.
• Habit: can be straggly, prune hard after flowering.
• Group: Maddenia.
• Species distribution: Sikkim, Bhutan in a variety of habitats including dense forest, open ridges, rocks and cliffs. Rarely epiphytic.
• Approximate altitude: 1,500 to 2,750m
• Ideal soil: pH 4.5 to 6.
• RHS Hardiness Rating: H4.

Good to know

Tender

Tender (maddenia) Rhododendrons are suitable for the cold greenhouse and mild areas such as Cornwall where they can be grown outdoors. Elsewhere in sheltered gardens they are worth trying against a South facing wall if temperatures are unlikely to go below -5°C. They give a magnificent display in spring, and the pinks and whites often have gorgeous scent to fill a conservatory. Many of these rhododendrons are epiphytic, meaning that they naturally grow in the boughs of forest trees and rock crevasses. Hence they often grow and flower better when their roots are constrained in a relatively small pot, and they need a very free draining (orchid type) compost, with just a teaspoon of slow release fertilizer.

When grown in a conservatory, these plants grow vigorously, so prune hard straight after flowering to encourage bushiness, leaving only about 10cm of the previous year's growth. They much prefer to be grown outside during summer months where there is fresh air and rainfall, so try to move out after frosts in May, and bring back indoors in October or November. Heating is usually not needed in the UK, and plants can be easily scorched if placed too close to radiators or heaters, or where there is lack of air movement within a conservatory.

Please note: Watch out for sooty mould on plants grown under protection (see advice centre for further information).

The Basics

Ideal soil

Acidic soil, good organic content, pH 4.5-6.0. Inkarho range of rhododendrons will tolerate soils up to pH7.5

Sun or Shade

Light dappled shade is best for most varieties.

Shelter

Refer to hardiness rating. Give young plants protection.

Site Selection

Avoid close to trees, roots, invasive weeds, walls, hot patios, dry banks and waterlogged soils. Do not use weed matting or stone mulch.

Plant spacing

Use the height shown in 10 years as a guide to the distance between each plant. Allow room for plant to fill out. If planting closer for instant impact, be prepared to move plants after a few years.

Compost

• 3 litre pot, dig in 10-20 litres of ericaceous compost.
• 7.5 litre pot, dig in 20-30 litres of ericaceous compost.
• 70-80cm specimen, dig in 60 litres of ericaceous compost.
• 100-120cm specimen, dig in 120 litres of ericaceous compost.

Planting depth

Plant high in the ground, with the top of the rootball visible.

Feeding

Slow-release ericaceous feed recommended in March and straight after flowering.

Mulch

Recommended every few years.

Water

The key ingredient! Keep moist all season, especially the critical time at end of June for flower bud initiation. Tap water is better than no water. Heavy dose at least once per week in dry weather.

Drainage

Ensure good drainage in winter, especially with yellow flowering varieties. Avoid waterlogged sites.

Pruning

Rhododendrons and Camellias: Not normally required. Tidy wayward shoots after flowering.

Evergreen azaleas and Bloombux can be clipped into a low hedge.

Magnolias and Acers: Formative pruning when young to shape into a tree or bush.

Deadheading

Remove old flower-heads, particularly on young or weak plants.

For further advice see here

Size Guide

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