Mamma Mia!: Anna Pavord discovers an Italian garden in Herefordshire

The Wellingtonia (Sequoiadendron giganteum) was the big new discovery of the 1850s, the wollemi pine of its day, introduced with just as much fanfare and drum-beating. More than 150 years on, these vast trees, named after the famous Duke who died in 1852, have made an indelible impression on the landscapes where they were first planted. Thanks to clever marketing by the Exeter nursery firm Veitch, anyone who had space had to have one. If you've read Thomas Pakenham's Meetings with Remarkable Trees (Cassell paperback £9.99), you'll know the story. Veitch had sent the Cornishman, William Lobb, to California to look for new plants. It was Gold Rush time and Lobb heard that a prospector had found a grove of extraordinary trees growing in the Sierras of Calaveras County, 200 miles south-east of San Francisco.

Lobb found the trees, 300 feet high, 70 feet round the trunk, and gathered as much seed as he could carry. Then he caught the fastest sailing boat available to get him back to England. Within a year, Veitch was selling seedlings at two guineas apiece; those seedlings are now trees more than 150 feet high (the tallest at Castle Leod in the Highlands is 174 feet) and loom up in parkland all over the country, unmistakeable markers of mid-19th-century one-upmanship among the gardeners of Britain.

Herefordshire is peppered with them; wandering around recently in the strange country either side of the River Wye between Hereford and Ross, I kept seeing them, rising out of ridges, dominating parkland, overspilling village verges. Perhaps it wasn't surprising; alongside the real black and white stuff of the 15th century, Herefordshire has a strong strand of the later 19th century running through it, expressed in impossibly baronial houses and fake timbering.

But even if you had the real thing, as the owners of Holme Lacy, one of Herefordshire's grandest houses did, you still wanted the Wellingtonias as well. I turned up there, expecting a 17th-century deer park to go with the 1670s house, and found Wellingtonias bobbing up all over the place. The house has been turned by Warner Leisure into a hotel and it's difficult to escape the ramifications of that: the lighting, the car parks, the signs, the double yellow lines, the fitness centre... But the yew hedges are good, bulging now in all directions and obviously in the hands of a creative clipper who is encouraging them into vast, amorphous bastions.

We now, trolling along the byways, are getting the benefit of all that busy Victorian planting. Sloping down to the west from Woolhope in Herefordshire is a wonderful spread of parkland studded with trees in their prime – the fern-leaved beech looks particularly lovely. And yet the people who planted them knew they were never going to see them at their best. It was a gift to the future, as the grove of redwoods (Sequoia sempervirens) at Whitfield was, planted by the Reverend Archer Clive in 1851 and now the biggest group of redwoods in Britain. The tallest is 148 feet high, towering above the rest of the trees in the woodland walk, a mile and a half long, that is one of the great treats of this lovely place.

Splendid trees also dominate the garden laid out through the valley below How Caple Court in Herefordshire. It intrigued me, this place, slipping quietly back into the undergrowth, stone columns broken, pools choked, seats cracked. But, as garden visitors, we're not allowed much of this any more (the dragons of the National Garden Scheme who control entry to the famous Yellow Book disapprove of weeds and decay). There's a part of me that loves the quiet melancholy of a garden like How Caple Court, going, going, gone.

From the yard (wonderful great tithe barns), you wander up the drive to enter the garden by The Dell, a grassy swathe leading down through fine swamp cypress, yew, sweet chestnut and oak to the huge lawn once occupied by two tennis courts. On the left is a long, low pavilion with a vast curved bench inside, big enough to seat at least eight. A raised stone walk runs round the lawn, with abandoned, terraced borders running back up to the house on its east side. Laid out by Alan Bloom of Bressingham (recent history, in garden terms) some survivors still wave through the weeds – campanula, Geranium psilostemon, crocosmia.

Below the tennis lawn lies the most extraordinary (and most ruinous) part of the garden. First there's a round pond, approached by wide, formal steps under a leaning walnut, weeping its fruit on to the grass. The pond is surrounded by oddly made stone pillars, connected around the top by sagging wooden beams. Beyond, now submerged in the undergrowth, are signs of a complicated rockery.

Beyond again is an even more unexpected element, a piece of Italy, with a vast curved stone seat and olive jars on a raised dais that must once have looked out over something now gone. Then, below that, a stone-paved Florentine Garden with a criss-cross channel of water, clipped Irish yews and a pretty little casita with another enormous bench. From here, you start the climb back up to the terraced gardens on the south side of the house, elegantly laid out (and maintained) with more curved stone seats like the ones that Harold Peto was so fond of, and another summer house (wood and tile) with a ravishing view out over the Wye valley to the Welsh hills beyond.

Who did all this work? Because that's another strange thing. The garden doesn't show up in any of the places you usually look for answers. I'd guess it all happened after 1900, when Lennox Bertram Lee, who has left his initials all over the place, came down here from Manchester. He had been a big cheese in the Calico Manufacturers' Association and must have had a lot of cotton money to spend. And the LCLL to whom LBL dedicated the great swamp cypress in the Italian garden? You'll find that answer, a poignant one, inside the church.

There are Historic House Tours at Holme Lacy House, Holme Lacy, Herefordshire HR2 6LP on Tue, Thur and Sat at 11am, when the house, as well as the garden, is shown, tickets £5, call 01432 870870 to book. The garden is open Tue, Thur, Sat (11.30am-5.30pm) and Sun (2-5.30pm) until 29 Sept, admission £3. Visitors to Whitfield, Wormbridge, Herefordshire HR2 9BA (01981 570202) are welcome but by appointment only; admission £3.50. The garden at How Caple Court, How Caple, Hereford HR1 4SX (01989 740626) is open daily (10am-5pm) until mid-Sept, admission £3