The sign on the gate states “Private. No access.” We ignore it and follow a path past a Georgian manor house, its white walls glowing pink in the early evening light. It appears to be empty but as we tiptoe past the large sash windows, I have the uneasy sensation of trespassing. To the far side of the house is a latticed wooden gate, which has been left off the latch. The lawn and flowerbeds in front of the house are neatly manicured, but on the other side of the gate is something altogether wilder. We set off down a narrow path that descends steeply through a lush valley spiked with palm trees and soaring Monterey pines. There’s the sound of trickling water from a waterfall and the leaves of flame-coloured crocosmia tickle our legs as we brush past. At every twist in the path there are new wonders: towering tree ferns, a grove of bamboo 10 metres high, a swathe of rampant hydrangeas with flower heads the size of footballs in every shade of lilac and blue. It’s like a sub-tropical Secret Garden on steroids, and we’ve got it all to ourselves. Tumbling down to the River Helford, Trebah is one of Cornwall’s best-loved gardens. The sublime coastal setting and exotic planting attract about 110,000 visitors a year, but from this month a few lucky people will get to experience this magical place with nobody else around. The Edwardian gatehouse at the entrance to Trebah has been renovated and turned into a two-bedroom holiday cottage that comes with a very special perk: after-hours access to the 10-plus hectares (26 acres) of this botanical wonderland. Within minutes we’re swimming in the clear water and basking in the novelty of having a beach to ourselves in Cornwall Even if you had no interest in gardens, this arts and crafts-style house would be a wonderful place to stay. From the two cosy lounges, with their velvet sofas in shades of olive and gold, botanical prints and antique cabinets full of natural history books to the huge kitchen and beautiful en suite bedrooms with iron bedsteads and panelled walls, every nook and corner has been carefully considered. It’s gorgeous, but within minutes of arriving we’re heading back out the front door, swimming costumes and towels tucked under our arms because Trebah has another trick up its sleeve – a private beach at the bottom of the garden. By day this sheltered pebble cove is busy with garden visitors picnicking, paddling or queueing for ice-creams at the beach kiosk, but by the time we arrive at 5.30pm it’s deserted. Within minutes we’re swimming in the cold, clear water and basking in the novelty of being in Cornwall in August and having our own beach. By the time we start the uphill walk back to the lodge, the light is fading and the garden is hushed and still. We cut through the gunnera plantation. Known as giant rhubarb, these Brazilian bog-dwellers can reach five metres in height with leaves more than two metres across. The mood now is less Secret Garden, more Arthur Conan Doyle’s Lost World. In the eerie green twilight beneath the canopy it’s easy to imagine a tendril coiling out and pulling us down into the swampy undergrowth. When the sun came out it was easy to imagine yourself in Madeira as you followed the path to the private beach Some of the more impressive tree and plant specimens at Trebah date from the 1800s, when Charles and Sarah Fox set about turning this sheltered south-facing valley into a garden. The Foxes were a wealthy Quaker family from Falmouth who had made their fortune in mining and shipping. Their links to the Falmouth Packet Company would have given them access to shipments of exotic plants from around the world. Many of the tree ferns now flourishing here would have arrived as ballast on ships travelling from Australia, before being thrown overboard in Falmouth harbour. The fascination with horticulture clearly ran in the family. Next door to Trebah is Glendurgan garden, which was laid out by Charles’s brother Alfred and his wife Sarah, who described it as “a small peace [sic] of heaven on earth”. Their descendants still live in the house but the gardens are managed by the National Trust. As with Trebah, it’s the antithesis of a polite English country garden, the mild, damp micro-climate encouraging familiar species like camellia, rhododendrons and hydrangeas to run riot. You can see a recreation of the small thatch-roofed schoolroom where Sarah and Alfred’s 12 children were educated, get lost in the cherry laurel maze (we had to admit defeat and climb over a gate to escape) and explore the tiny fishing hamlet of Durgan, with its cluster of cottages now run as holiday lets. The green-fingered Foxes were also responsible for the gardens at nearby Penjerrick and the beautiful grounds of the Hotel Meudon, where we checked in for a couple of nights before arriving at Trebah. A Victorian redbrick house with a modern wing of guestrooms, this gem of a hotel was family-run until 2021, but still retains a friendly, relaxed feel. We loved the light-filled rooms with their mid-century lamps and sofas, the airy conservatory-style restaurant serving elegant dishes of locally sourced food, and the sense of being cocooned in those lush gardens. When the sun came out it was easy to imagine yourself in Madeira or Corsica as you followed the path down to the hotel’s private beach, Bream Cove. From here you can join the coast path and head north towards Falmouth or south to the peaceful creeks and coves of the River Helford. At Helford Passage we sat on the sunny harbourfront terrace of the Ferry Boat Inn and watched as families in wetsuits launched themselves into the water on paddleboards and kayaks. Even in August this peaceful corner of Cornwall feels far removed from the crowds and traffic jams that can choke some of the coast’s more popular spots. There are plenty of low-key delights to visit along the river, from the seal sanctuary at Gweek to the charming village of Port Navas, renowned for its oysters. But whenever we ventured out, it wasn’t too long before we felt the call of our garden oasis pulling us back into its leafy embrace. Accommodation was provided by Trebah Lodge and the Trebah Garden Trust. The lodge sleeps four and costs from £815 a week through Cornish Holiday Cottages. There is limited availability left for 2025. Hotel Meudon has doubles from £119 B&B