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Lagerstroemia

Time was that Lagerstroemia were as rare as hen’s teeth in UK gardens, but now visitors to RHS Garden Wisley can peruse a National Collection of 60 of these flamboyant shrubs or small trees, all growing and thriving outdoors. They can mostly be found in the Bowes Lyon Rose Garden, Rock Garden and Heather Garden.

Travellers to parts of the world with a Mediterranean climate are likely to have encountered the genus Lagerstroemia, also known as crepe myrtles. In some places their gaudy, ruffled, taffeta flowers in white or shades of pink and purple are almost ubiquitous. What may be puzzling to gardeners is that those places often record winter temperatures similar to those experienced in the mild, maritime UK and yet, in most areas, until recently Lagerstroemia rarely survived a British winter unprotected. 

The key to the mystery is not so much winter cold as summer heat. Without a sustained spell of hot weather to ripen the wood, the soft growth produced in summer will be vulnerable to frost in winter. However, as temperatures have climbed in the UK, especially in the south and in urban zones, crepe myrtles have become increasingly valuable garden subjects. This was demonstrated by the RHS Trial of Lagerstroemia, held at RHS Garden Wisley between 2019 and 2021, which showed that in some British gardens these are now plants to be reckoned with.

Lagerstroemia indica EVELINE (‘Lage001’PBR) 
When the old Trials Field was decommissioned in 2021, 35 entries were moved into the garden. This formed the basis of the National Collection and delighted Emma Allen, RHS Head of Horticultural Relations and the Collection’s custodian.

“I fell in love with crepe myrtles when I saw Lagerstroemia indica while working at Borde Hill, West Sussex, years ago,” she explains. “It was growing against a south-facing wall and we were thrilled one long, hot summer when it flowered really well. Now they seem to flower reliably and there has been an avalanche of recent breeding. It’s super exciting.”

Emma added another 25 cultivars from Minier Nurseries in Anjou, France, and National Collection status was awarded in 2022. Some of these cultivars are so new to the UK that, though the trial has ended, they continue to be assessed for the Award of Garden Merit.

“Lagerstroemia have so much to offer,” Emma enthuses. “Besides the flowers, many have great autumn colour and some have lovely bark so there’s winter interest too. They come in a variety of forms, including dwarf cultivars that are good for rock gardens and containers.”

Lagerstroemia have so much to offer. Besides the flowers, many have great autumn colour and some have lovely bark so there’s winter interest too.

Emma Allen, RHS Head of Horticultural Relations

Cultivating crepe myrtles

Though Lagerstroemia are now finding their feet in the UK, care still needs to be taken to grow them well and in many areas of the north they remain off the menu. Where they are being tried outdoors, be sure to choose a spot that is sheltered from cold winds but also bright and sunny. A position by a south-facing wall where they can get a good baking is ideal. Soil should be well-drained and reasonably fertile. The panicles of showy flowers are usually at their best in August but may appear as early as July and go on into September or beyond.


Deciding which to pick

“There’s so many to choose from that you might need to come to RHS Garden Wisley to help you pick!” encourages Emma. “I don’t like to give recommendations because I appreciate them all for different reasons but for growth habit I really like Lagerstroemia ‘Acoma’. It’s a multi-stemmed hybrid with a strongly upright form and white flowers. It could be great for a large container. As a contrast, there’s L. indica ‘World’s Fair’ which has pink flowers and weeping branches.”

Lagerstroemia ‘Acoma’
Lagerstroemia indica ‘World’s Fair’ 
Good all-rounders? 

“Lagerstroemia LUNAR MAGIC (‘Baillagone’) has a neat habit, gorgeous deep-purple leaves and lots of white flowers. Lagerstroemia indica RHAPSODY IN PINK (‘Whit VIII’) is another good dark-leaved cultivar with pink flowers.”

Lagerstroemia indica RHAPSODY IN PINK (‘Whit VIII’)
As the climate changes, the suite of plants that will thrive in UK gardens is liable to change with it. Whatever the future holds, by trying and testing plants in its Gardens the RHS aims to be able to give sound advice on those that will cope with the conditions presented. The National Collection of Lagerstroemia is likely to have an important part to play in that effort.

Lagerstroemia indica BRAISE D’ÉTÉ (‘Indybra’PBR) (Indya Charms Series) 

About the author - James Armitage

James only discovered a love of plants in his late teens but learned quickly thereafter. After gaining an HND in Plantsmanship at Royal Botanic Garden Edinburgh, he completed a master’s degree in plant taxonomy at University of Reading. He started as a botanist at RHS Garden Wisley in 2002 and published widely in botanical journals and popular horticultural magazines. He made the move to publishing in 2018 as editor of the RHS periodicals The Plant Review and The Orchid Review. 

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