Tregrehan Garden: A Story of the Carlyon Family, a Spectacular Arboretum, Plant Hunting Expeditions and Cornwall’s Temperate Rainforest

As we’re discovering in this series, each of the fourteen Great Gardens of Cornwall has its own rich history and individual character.


These spectacular Cornish gardens deserve to be recognised and celebrated, as together they represent the depth, breadth and marvellous variety of gardens in the region.

The next garden we’re exploring as part of our Behind The Gardens Campaign, is the beautiful Tregrehan Garden, which sits in a sheltered spot at the head of St Austell Bay. It’s a botanical sanctuary of temperate rainforest and parkland, with a walled garden and a spectacular glasshouse range – there is so much to explore here.

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A Carlyon family owned garden for centuries


Tregrehan has been in the Carlyon family since 1565, and remains a family run garden to this day. It prides itself on taking a personal approach, and visitors to the garden will enjoy a very ‘non-commercial’ experience. Like its many Southern Hemisphere plants, over the years four generations of the Carlyon family have also migrated from New Zealand to Cornwall in order to take the helm of the family estate.

In 1845, parts of Tregrehan Garden, especially around the house, were designed by the talented WA Nesfield, the same architect who designed the structures around the palm House at RBG Kew. The Carlyons were a mighty family in their day, with strong connections and ambitious plans, so there is a fascinating history to unpick here, and an incredibly special garden to celebrate as a result.

Because the estate has been passed down through the generations, it has benefited from consistency, stability and growth. The garden has evolved over the centuries as each custodian has ploughed energy into their particular passion projects; four hundred and sixty years of family ownership has created an amazingly robust foundation. In the 1730s Philip Carlyon, who was a mining entrepreneur by trade, but a horticultural entrepreneur by nature, made references in his diary of selling laurels, elms and oaks to other Cornish estates. He also made great strides planting larch, fir,walnut, chestnut and beech trees at Tregrehan. In the 1880s Jovey Carlyon engaged with international plant hunting exotica and brought a wealth of variety and novelty to the garden, much of which is still in bloom today. The current guardian of Tregrehan is Tom Hudson, a cousin of Gillian Carlyon, who was living in New Zealand in 1987 when he answered the call and returned to Cornwall to take on the restoration of Tregrehan and create Cornwall’s temperate rainforest.

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Tregrehan Plant Nursery


As well as developing and nurturing plants for its own garden, the nursery at Tregrehan has a long history of propagating plants for sale to other gardens and visitors. In fact the nursery has been propagating and selling plants here for about 300 years! Long before the infamous plant hunting expeditions to farflung shores, the nursery at Tregrehan was well stocked and doing a booming trade in hardy Cornish varieties. Just behind the glasshouse you’ll find a propagation house, dedicated purely to the raising of stock from seeds and cuttings.

As you enter Tregrehan you’ll see a small sales display showcasing a selection of plants, such as camellias, including some of the Carlyon hybrids, bare root rhododendrons and other shrubs and trees that do well in milder gardens. When raising rare seeds at Tregrehan, surplus seedlings are often potted and offered for sale as ‘extras’ – so it’s well worth pausing here for a little dig around, as you can often find extraordinary plants for sale that you won’t find elsewhere!

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The Tregrehan Glasshouse


The glasshouse runs 60 metres along the walled garden, and is nothing short of spectacular; there aren’t many buildings of this type, age and size in existence in the UK. It’s an imposing but beautiful structure that defines the experience of the walled garden. Originally built in 1845 from close-grained timber, with sliding sashes for ventilation and a boiler for the all-important heating, it was used as a heated show house for tropical plants such as camellias, orchids and vines. These days, although the old boilers are still in situ, they aren’t in use, so the glasshouse is simply used for frost protection for those plants that require it, such as fruits, climbers and display shrubs. Tom Hudson led a huge renovation effort in the 1990s to replace much of the glass in the roof and shore up the structure of the iconic glasshouse.

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Eden Project Cornwall
Eden Project Cornwall

First an arboretum then a woodland garden


The plant collection at Tregrehan, especially the trees, are amongst the most notable in the West Country. Approximately 200 trees at Tregrehan are the tallest or widest of their kind in the British Isles. The sheer size and variety of evergreen or coniferous trees makes Tregrehan a rewarding garden to visit year round.

Upon conception, most valley gardens in Cornwall and the South West used the existing native canopy or natural topography of the land to create their woodland microclimate. Tregrehan is different, in the middle of the 19th century the garden was planted as an arboretum – a place for the scientific study of trees. The concept of arboretums dates back to the ancient pharaohs of Egypt, who raised and studied trees to deepen their understanding of the natural world.

The reputation of Tregrehan’s arboretum spread quickly, and in 1914 JC Williams (of Caerhays Estate) introduced a representative from the Arnold Arboretum (in Boston) to Tregrehan, who claimed that “Tregrehan is the best thing of its kind in the world” – amazingly high praise for such a young and still developing arboretum. By 1916 both WJ Bean and Jackson from RBG Kew, had also visited Tregrehan and penned articles about the richness of the tree collection.

It was later that the arboretum at Tregrehan grew into a woodland garden, as the understory filled in and the canopy developed. Owen Johnson from the British Tree Register recently described Tregrehan as “the finest private garden in Britain and Ireland for its range and size of recently introduced tree species.” Johnson counted Tregrehan to have over 170 National Champion trees, which puts it in the top echelon of collections in the nation. Tregrehan also boasts a Picea sitchensis, (sitka spruce) which at 153 feet is the tallest tree presently on record in Cornwall.

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A history of plant hunting expeditions and exotic seed collection


In the mid 19th Century, plant hunting expeditions enabled a supply of previously unknown seeds to be grown in Cornwall; suddenly spring and early summer flowering rhododendrons began to be planted in the garden, livening up the woodland with their riot of colour. Today, there are still original plants which hail from this historic era, now matured to an enormous size. A lot of these first species – Rh. grande, arboreum, falconeri, hookeri and barbatum – descended from seeds introduced by Joseph Dalton Hooker, Director of the Royal Botanical Gardens at Kew and best friend of Charles Darwin.

In 1880 Jovey Carlyon returned to Cornwall from New Zealand, where his father had emigrated thirty years before. Jovey planted every new seed he could get his hands on, from all over the New World, in addition to ordering from established Nurseries like Veitch and Smith. Much of Jovey’s planting has survived, and now forms the backbone of the more mature Tregrehan. Jovey was a fastidious record keeper and his planting notebooks have been preserved for future generations.

In a letter sent from India dated 1st July 1894, Gilbert Rogers, a Cornish forrester and plant hunter wrote to Jovey Carlyon:

“My dear Carlyon, it is so hot down here that I find it impossible to write decently. I only came down from the hills yesterday… I am writing to tell you that I have sent you a box containing some seeds of Quercus semecarpifolia in charcoal … the acorns may have all germinated on the way as they germinate here almost as soon as they fall to the ground but I hope that some of them, if they have germinated, will reach you alive. This species of oak covers the highest hills in Yarmsa and grows at elevations above the spruce and mixed with the silver fir, so should do well with you. It is very hardy, grows very slowly and makes a fine tall straight stem if grown in close canopy….”

This particular batch of seed travelled all the way from India in 1894 and was the first of its kind to be grown outside of the Himalayas; the proud oak tree now stands 25 metres tall at Tregrehan.

At Tregrehan, the original 19th Century rhododendron collection has been fortified over the generations, notably by Rupert Carlyon, who in the 1930’s planted with Wilson and Forrest seed. Current owner Tom Hudson has also made a great impact over the last 25 years, most of his colourful additions have been nurtured from wild seed in the Tregrehan nursery before being planted to make a noticeable positive impact in the garden.

William Lobb and Harold Comber were also pivotal in the introduction of many Southern Hemisphere trees and shrubs which thrived in the mild Cornish climate. At Tregrehan, the South American Nothofagus spp. has proved to be successful in the woodland garden, and the Gondwanaland Section of the garden showcases many Tasmanian and South Australian plants such as Proteaceae, Embothrium and Grevillea.

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Eden Project Cornwall

A garden where camellias thrive and family hybrids are on display


The first camellias were planted along the edge of the Walled Garden where the brickwork could provide shelter from the cold. However they soon grew too tall for the garden walls, preferring the conditions of the woodland garden in which to thrive. A number of original 1840’s Camellia japonica plants are still visible in the garden, proving the genus to be a hardy and durable one, well suited to the Cornish climate. Over the years the trunks have thickened to become almost tree-like, and are certainly amongst the oldest Camellia plants grown outside in the UK today. Gillian Carlyon made her mark in the field of camellia hybridisation, and around twenty of her varieties were named and can be admired in the top section of the garden.

In recent years Tom Hudson has added a camellia spp. species collection to the garden. They originate from areas of low elevation in Southern China and North Vietnam, however seem to be flourishing outside at Tregrehan in all but the most extreme temperatures. These new and colourful additions to the Tregrehan foliage are scented, and many have coloured bark and interesting variance in the shape and size of their leaves, adding visual interest to the garden year round.

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Not just the classic magnolias


Most visitors will be familiar with the large Asiatic tree magnolias that dominate Cornish gardens in early spring, and Tregrehan has plenty of these stunning blooms which vary in colour from white to deep crimson red. However Tregrehan also has in the garden two types of evergreen magnolia, Michelias and Manglietias, which vary in stature from bushes to tall trees. They flower later in the season and fill the woodland garden with glorious scent; in many parts of the UK these magnolias wouldn’t stand a chance, but here in the sheltered depths of the garden at Tregrehan, they thrive.

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A peaceful setting and a personal journey around the garden


Visitors always comment on the peaceful feeling they get when they visit Tregrehan. There aren’t too many arrows or signs and it has a very natural feel about it. You don’t feel like you are being shepherded around on a conveyor belt, instead you’re able to instinctively navigate, and explore the areas of the garden you feel drawn to.

The parkland that wraps around Tregrehan is around 50 acres in size and has evolved over the centuries from a collection of smaller enclosures into the picturesque sheep grazed pasture we see today. The sheep graze as part of the Higher Stewardship Scheme, mandated by Natural England, which requires an organic regime to promote the biodiversity of this ancient wood pasture system. English Oak and Sweet Chestnut trees are present here, but in addition, over 150 trees have been introduced to the park in a renewal scheme. Many trees here are over 350 years old, so their replacements have to be waiting in the wings for this garden to continue to evolve for centuries to come.

The middle of the garden is Tom Hudson’s favourite part of Tregrehan, as it has the best views down into the valley and it is the most sheltered area for tender and important plants, many of which are critically endangered in their native habitat.

Which is your favourite part of Tregrehan Garden? If you haven’t yet visited, there is only one way to find out!

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Visit Tregrehan


  • During spring, Tregrehan Garden is open four days a week from Friday March 15th until Friday May 31st 2024, Wednesday, Thursday, Friday and Sunday from 10:30am – 5:00pm.
  • During summer and autumn, Tregrehan Garden is open from June 5th – October 30th, on Wednesday afternoons 1:00pm – 4:30pm.
  • The garden is also open at other times by appointment and group visits are welcome at other times by arrangement.
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