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Magnolia grandiflora

The RHS Wisley National Collection of Magnolia grandiflora includes 29 different kinds, with one species and 28 cultivars. The collection has been a special interest of two curators and includes three champion trees.

Standing strong and green, Magnolia grandiflora has a grace and beauty that persists all year round. Flowers aside, the evergreen leaves alone are an ample ornamental feature – large and glossy deep green with beautiful rusty brown undersides.

From late June to autumn, these magnificent trees start to reveal further delights in the form of dinner-plate-sized flowers that almost defy belief. Creamy white petals announce the opening of flowers with the most exquisite scent. Magnolia grandiflora flower sporadically, so rather than flowers covering the whole tree at once, as with the spring-flowering magnolias, you’ll see a few large individual flowers dotted high and low across the tree canopy at any given time.

Magnolia grandiflora
Magnolias are one of the most ancient flowering plants, and fossil records show they existed in Europe, North America and Asia during the Cretaceous period, as far back as 95 million years ago. While there were dinosaurs at that time, bees did not exist yet, so magnolias evolved to be pollinated by ancient beetles. 

Magnolia grandiflora is native to the southeastern United States, from East Texas to North Carolina. Its native range was previously much wider, but it is no longer found in Europe apart from in gardens.

RHS Garden Wisley holds the National Collection of Magnolia grandiflora cultivars, which includes three champion trees - the largest trees of their species growing within the British Isles. RHS Vice President Jim Gardiner increased the cultivated collection during his 22 year tenure as Curator at Wisley and it was then expanded further by former RHS Wisley Curator Matthew Pottage and registered as National Collection with Plant Heritage in 2022. Matthew Pottage recognised Magnolia grandiflora as a good climate-resilient tree for the future in places like Surrey, equipped with a love of heat and tolerance of dry conditions.

Magnolia grandiflora cultivars are now being put to the test in some of the toughest parts of the garden, characterised by poor soil and exposed conditions, to see how they handle the worst of the weather.

James Lidgett, a horticulturist at RHS Wisley and Team Leader for the School of Horticulture, has taken on the role as custodian of the National Collection – an important responsbility that he relishes.

“There are two aspects to being a custodian. Firstly, I’m looking after some of our rare cultivars and our three champion trees, which are the largest of their kind in the UK and Ireland. Some of these are cultivars not easily available in the trade any more, so we can demonstrate what a tree looks like when it is cared for over a long period of time.

“Secondly, this is an opportunity to look at trees for the future. We will be able to look at new introductions and see which ones thrive. We’ve planted some in tough conditions and our learnings may help to tell us what will be good for the future, whatever the climate throws at us,” he said.

“RHS Wisley has some incredible trees dotted around the garden. The cultivar ‘Nannetensis’ sits next to one of the lakes on Seven Acres – a small squat tree.

“There are also three champion trees at RHS Wisley. ‘Charles Dickens’, which is a very rare tree, can be found near the The Old Laboratory. It’s 15m tall and 10m wide – broad, squat and free-flowering with blooms around 25cm across. People can see and smell the flowers at face level, and it has this incredible spicy lemon scent.”

Another champion tree, ‘Victoria’, is behind the Pines building, adjacent to the Walled Garden and the third, ‘Saint Mary’, is located outside Gardiner’s House, beside The Old Laboratory.

Magnolia grandiflora ‘Nannetensis’
Magnolia grandiflora ‘Saint George’
There is a ‘Saint George’ cultivar planted next to Gardiner’s House on the other side of the lawn, near ‘Saint Mary’, which was propagated from a specimen at RHS Hyde Hall.

There are now a number of young trees in the rose garden near RHS Hilltop, including the common ‘Kay Parris’ cultivar, which is common for a reason: excellent flowers, reliable, a lovely brown colour on the underside of the leaves – “a good showy plant”, according to James.

Magnolia grandiflora ‘Kay Parris’
The National Collection includes a special tree, ‘Mont Blanc’, one of custodian James’ favourites. It is a young tree with remarkable flowers – up to 40cm wide – and lives in the Exotic Garden at RHS Wisley. It is a summer star, coming into flower in late June and flowering sporadically all the way through summer into autumn.

© Milan havlis
Magnolia grandiflora ‘Mont Blanc’
In the Dry Beds, close to The Walled Garden and Oakwood, there is a straight species Magnolia grandiflora. “It’s likely to be our oldest magnolia at over 100 years old,“ said James. “It has layered itself several times (it's branches getting so heavy they have rooted in the ground), so is full of character. It forms big walls of foliage and blocked some views of the garden, so we decided to raise the crown and reveal the views. I have come to admire this amazing tree, with its tough, resilient nature and deep green foliage.

“The cultivar I particularly like is ‘D.D. Blanchard’, which has deep chestnut brown coloured leaves and has a hairy underside to its leaves. When the sun shines on it and the wind blows, you get such a striking effect. I really like ‘D.D. Blanchard’ – it makes an impression both close up and far away – and we have a couple of young ones at RHS Wisley. On a sunny day, I’ll make a beeline for them.”

Magnolia grandiflora ‘D.D. Blanchard’
Magnolia grandiflora ‘Charles Dickens’
As part of the National Collection, RHS Wisley is growing and trialling a new tree called ‘24 Below’, which is said to be able to cope with extremely low temperatures.

© Asperupgaard
Magnolia grandiflora ‘24 Below’
“The differences between Magnolia grandiflora cultivars can be subtle. You have to really pay attention, and I like that. It’s been a journey for me to start learning and appreciating them.”

“Magnolia grandiflora drop their leaves all year round, even though they are evergreen. In late June and early July they have a big leaf drop and can look slightly unhealthy for a while, but then they push out new leaves, so their foliage looks clean for most of the year.”

Magnolia history

The Magnolia genus was named after French botanist Pierre Magnol (1638-1715), who was Director of the Royal Botanic Garden Montpellier. Plant collector Mark Catesby brought the first Magnolia grandiflora to the UK in 1726 from North America. It entered cultivation and quickly overshadowed M. virginiana, the other North American evergreen magnolia, which had been collected a few years earlier. It is thought to have also arrived in France and Spain around the same time, being collected by the French from the area around the Mississippi River in Louisiana.

Magnolia grandiflora is still an iconic and symbolic tree in some US states, celebrated in the South for its cultural and spiritual significance, and is the State Flower of both Mississippi and Louisiana.

Growing conditions

Magnolia grandiflora can tolerate some damp conditions as they naturally grow near water sources, but they don’t like to be flooded. They are resilient to a wide range of conditions and pollution – James has even seen them planted as street trees in Spain and Turkey, and hopes we might see more in the UK. The trees can be easily shaped and pruned and are very versatile.

The tallest tree has reached 37m in the USA, but it doesn’t grow that tall in the UK, where they tend to be broad and squat and grow more slowly – closer to 15m tall and wide when left to their own devices. In the Mediterranean, Magnolia grandiflora can grow vigorously and upright. They have proven to be generally reliably hardy in most of the UK, especially in the South.

“We grow them in the open at RHS Wisley, with everything that entails during our winters, and they don’t struggle with that,” said James.

The magnolias at the RHS Gardens can be admired from March, when the deciduous species come into bloom, and through the summer when Magnolia grandiflora takes over. Keep an eye on RHS social media so you don’t miss them in all their glory, or even better – come and see them and inhale that dreamy scent for yourself.

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