Rhododendron: succeeding in its planting

Where to plant the Rhododendron?

Versatile, Rhododendron fits into all décors and can be used both in borders with perennials, at the edge of woodlands, to dress a wall, in a free hedge alongside other heather soil shrubs (Magnolias, Pieris, Camellias, Heathers…), as well as in isolation or in pots on a shaded terrace.

Plant the tallest varieties in a sheltered wooded area, at the edge of woodlands in the back of a border or as a hedge. Plant dwarf Rhododendrons in fresh rockeries or along the edges of flower beds exposed to partial shade. With very slow growth, Rhododendron is a compact bush that suits small gardens or urban gardens well.

Vigorous, it grows throughout France, except perhaps in Mediterranean climates, as it fears scorching sun and drying exposures. Endowed with very good hardiness, it is not afraid of the cold, withstands frost, and tolerates temperatures below -20 °C. It thrives in a rather shady spot, sheltered from strong winds, along a wall or under the dappled shade of large trees. Ideally, it prefers northern or north-western exposures.

Rhododendron needs shade and coolness to thrive and requires an acidic soil, rich in humus, ideally close to heather soil and not calcareous for proper development. The soil pH should be between 5 and 6.5.

It fears heavy, compact, suffocating soils and prefers fresh ground where water never stagnates.

When and how to plant Rhododendron?

Rhododendrons are planted in spring from March to April after the frosts or in autumn from September to October, after the heatwaves, which will encourage their establishment.

If you are planting Rhododendrons side by side to create a thicket, space them 1 to 2 m apart in all directions.

How to plant?

In the ground, in the garden:

• Avoid areas where water stagnates as well as calcareous soils. In heavy soils, add gravel, pumice, or a good layer of clay balls at the bottom of the planting hole to ensure good drainage (its roots do not like stagnant moisture, especially in winter).
• Soak the root ball for 10 to 15 minutes in a bucket of water before planting.
• Using a spade, dig a hole three times wider than the pot and 40 to 50 cm deep: it should not be planted too deeply.
• Plant the bush at collar level, in a mixture ideally composed of 1/5 good soil mixed in equal parts with peat, heather soil, leaf mould, and pumice.
• Spread an organic mulch of pine bark 8-10 cm thick or plant small perennials to protect the base and limit watering: it likes its roots to be kept cool during summer.
• Water regularly with non-calcareous water (rainwater), twice a week for the first 15 days after planting to keep the soil moist and cool. During the first year of planting, in summer and especially during dry spells, water abundantly.
• In calcareous soil, replace the extracted soil with a mixture of heather soil, leaf mould, and peat. Calcareous soils cause these bushes to yellow, a condition known as chlorosis, which often leads to their demise. You can also line the bottom and sides with a planting felt to prevent the rise of lime.

In pots, on the balcony or terrace:

• Choose dwarf varieties.
• Select a large container of about thirty litres (30 to 40 cm in diameter).
• Make a bed of gravel or clay balls at the bottom.
• Fill with a rich, very draining mixture based on true heather soil, well-decomposed compost, and good non-calcareous garden soil.
• Water regularly with rainwater only.
• Spread a mulch or install small perennials to retain moisture.