It's at a place called Wakehurst, thirty miles away in the West Sussex countryside. The National Trust own the estate, but leased it out to the Royal Botanic Gardens fifty years ago. It's got a fantastic 500 acre garden, but more importantly it's home to the world's largest wild plant seed bank. No rainforest plant is heading for extinction on its watch.
I'd always considered Wakehurst too far away to easily reach. According to its website the nearest station is Haywards Heath, 6 miles away, and that's a long way to hike there and back. There's a bus service, but no more than five buses a day, and none on Sundays or bank holidays. Stuff that, I thought. And then I looked on a map, and spotted that Balcombe station is only 2 miles away, and suddenly it looked a lot more possible. It only took an hour to ramble down and up valleys, cross fields and streams, pause to admire the view a lot, and arrive at Wakehurst's back gate. Not easy, but not hard, and no need to pay the £4 bus fare or the £10 parking charge.
Let's start with the seedy bit. The Millennium Seed Bank was opened by Prince Charles in in November 2000, its aim to collect and preserve samples of 25% of the world's seeds by 2020. They're up in the high teens already. Seeds arrive from all round the world and are tested, X-rayed, dehydrated and bottled before being frozen in vaults at a temperature of about -20°C.
The vaults form the storey below ground level, while upstairs are laboratories and a central visitor atrium, complete with glass walls so you can peer through and watch work going on. The process is explained in words and moving pictures, including how a zig-zag aspirator works and why certain recalcitrant seeds aren't suitable for storage, while the newest arrival is an arty neon filament sculpture. It's really interesting, though not a visitor attraction that'll detain you for long, certainly not as long as its two billion inmates.
Outside, however, the gardens could fill hours. They used to be the gardens of the chair of the Royal Horticultural Society, and he lived here for a third of a century, which is how the grounds got to be so diverse and glorious. They're about a kilometre across and oval in shape, with a big dull field in the centre which the rest of Wakehurst whirls around. Turn right on leaving the Visitor Centre and you may wonder what all the fuss is about. Turn left and you'll soon know.
A Tudor house, a big lawn and a cafe in the old stable block - that's standard National Trust fare. But beyond that the landscaped borders begin, and the gardens, and the water features, and the ravines. This part of the High Weald is characterised by steep-sided 'gills', which with a bit of judicious planting can look positively ravishing. Wakehurst's former owner Gerald Loder was a huge fan of rhododendrons, and it shows, with multifarious bursts of vibrant colour all over the southern half of the site, and April possibly the pitch perfect month to view. [10 photos]
It's also a perfect time to see the bluebells. They're everywhere in the locality at the moment, covering entire slopes in Horsebridge Wood within the Wakehurst site, as well as woody glades out in the wider countryside. I was quite excited when I saw my first ones, because it's been a while, and thrilled by the shady descent down to the Ardingly Brook when I was making my way into Wakehurst's secret rear entrance. But within a couple of hours I'd grown quite blasé of bluebells, having seen so many, and found myself able to walk past thousands without my camera finger even twitching.
There's nothing formal about the Wakehurst landscape, but instead twisty paths and forested ascents, plus some more wheelchair-friendly flattish bits mixed in. One section is packed with plants from Asia, another from the southern hemisphere, again frequently covered in cloaks of spring flowers. The Iris Dell in the Water Gardens was making visitors gasp yesterday, even though too early in the year for the plants after which it's named, thanks to the vivid magenta bushes covering one entire flank above the waterfall.
Find the right path and you'll walk amid gnarled roots and sandstone boulders on a Rock Walk, or stumble upon a viewpoint across a somehow not-artificial gorge. Expect too to meet several pheasants, which seem to be endemic in the locality, strutting across lawns and whirring out of the undergrowth, here safely out of the way of West Sussex's many shooting parties. I also found the beehives, and several willow sculptures, and the non-Cadbury Easter Egg Trail, and two ladies bemoaning quite how far they had to walk back to the car park.
A large lake at the very far end hints at the much larger Nature Reserve just beyond the gardens, so carefully protected that only 50 visitors are allowed each day to hunt for dormice, saxifrage and kingfishers around the tip of the Ardingly Reservoir. Maybe save that until a second visit, or a third, because there's more than enough to admire within Wakehurst's perimeter, particularly if you're a horticultural person. The next bank holiday's only a fortnight off, and the floral display might be almost as fine then as it is now.
Entrance is £12.50, but free to National Trust members, which I don't think I'd have spotted at the till if I hadn't known in advance. Absolutely nobody will challenge you if you walk in via the public footpath at the western edge, because virtually nobody does this, but obviously it would be wrong to peel off here and enjoy the gardens for free. I chose to walk back to Balcombe a different way, diverting via Ardingly and the rim of the reservoir, which was differently picturesque... and six miles in total, which was the distance I'd previously been so keen to avoid.