How to plant rhododendrons to brighten shady gardens

Rhododendrons are the perfect spring-flowering shrub for brightening up shady gardens.

RhododendronsGETTY

Rhododendrons can brighten up any garden

In the wild they are woodland plants, so they prefer dappled sunshine and can manage well in shade.

They also like plenty of water and because they were introduced to Britain by Victorian plant hunters from places like the Himalayas, they can also withstand cold temperatures.

What they don’t like, though, is chalky or alkaline soils or to be planted too deep, and although they need plenty of water they won’t thrive in boggy or badly draining soil.

As most rhododendrons sold in the UK are sold in pots, rather than bare-rooted, they can be planted at any time but between September and May is best.

Autumn planting has the benefit of giving them time to settle in and grow new roots before winter, so they are well-established by spring and can really start putting on some growth.

But March and April are absolutely fine, and you have the advantage of seeing what colour and size the flowers are when you go to your local nursery.

Once you come to plant your rhododendron, you can take it out of its pot and put the root ball in a bucket of water, just to make sure it is well hydrated.

And while it is having a soak you can dig the planting hole – two or three times the size of the root ball and far enough from other big bushes or trees that their roots won’t compete for moisture in the soil in summer.

The hole has to be wide so you can tease out the roots to encourage them to search for water, rather than grow round and round themselves.

Rhododendrons, which is Greek for Rose Tree, is the Horticultural Trades Association’s Plant of the Month for April 2015.

But don’t dig any deeper than the depth of the root ball because you need the soil to come up to the same height on the trunk as it did in the pot.

If you put a bamboo stick or rake over the hole you can use it as a guide when you are planting your rhododendron, to make sure the mark made by the pot soil lines up with the stick.

First, though, work some leaf mould or home-made compost into the bottom of the hole because they are both slightly acidic.

Composted Christmas tree branches are brilliant for this, or you could add well-rotted manure – but don’t use anything alkaline such as spent mushroom compost or bonemeal.

Hold the trunk as your fill the hole with soil, firming it down to prevent air holes, and then shuffle your feet over the top to finish it off.

Water well and add a layer of wood chips as a mulch to stop the water evaporating, and if there is a particularly hot spell make sure you water every few day – at least for the first couple of years.

Rhododendrons, which is Greek for Rose Tree, is the Horticultural Trades Association’s Plant of the Month for April 2015.

It recommended RHS AGM varieties include Rhododendron Bashful, Rhododendron Dreamland, Rhododendron Lavender Girl, Rhododendron Pink Pebble, Rhododendron Scintillation and Rhododendron Tortoiseshell Orange.

If you have alkaline soil, choose a compact hybrid that can be planted in a container or raised bed in ericaceous compost that you can buy from garden centres.

Top up the pots with leaf mould or home-made compost in spring, and add fertiliser before and after they have flowered, whether they are in a pot or not.

Spring-flowering companion plants recommended by the HTA include to Pheasant eye daffodils (narcissus poeticus), Corydalis ‘China Blue’, Euphorbia ‘Silver Swan’ and Pieris ‘Forest Flame’.

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