I’ve just been treated to the finest display of roses I’ve ever seen: a collection of around 1000 varieties of historic roses at Kartause Ittingen’s gardens in the Swiss Canton of Thurgau.

The visitor is greeted by a stunning blaze of colour bedecking the outer wall of the former monastery. Climbers and ramblers vie for your attention and suffuse the air with an indescribable fragrance.

You then stroll beneath a pergola along an avenue leading to a series of gardens, all brimming with climbers, bushes and weeping standards.

We owe this magnificent garden to the close co-operation between the Charterhouse Ittingen Foundation and the Winterthur Rose Society. Under its first president, Elisabeth Oberle, the society began planting in 1983.

As the society’s current president, Daniela Stuber, tells me, Elisabeth was a strong character who knew exactly what she wanted: a design to reflect the importance of roses to the monks.

She retained the garden’s oldest flowering rose, a wild Rosa canina specimen. As former rose society President, Magdalen Macher, says: ‘With her thick and gnarled branches and her powerful root, this rose is an impressive and worthy representative of ancient times.’

The Rose Society recognised Elisabeth’s pivotal role by commissioning the Louis Lens Nursery in Belgium to breed and name a rose in her honour. The octogenarian was thrilled to be at the planting ceremony in 2010.

I was fascinated by Elisabeth’s skill in selecting historic varieties that can be pruned and grown to suit different sites. This has continued under the direction of my guides, Daniela and Magdalen.

One of the first roses I saw at Charterhouse was the rambler, ‘Seagull’, with its mass of small white flowers. I was surprised it wasn’t trained against the wall, but grown as a wonderful large bush.

But all became clear when Daniela explained that the south-facing white wall was too hot to allow roses to thrive.

Climbers and ramblers are trained against the cooler, east-facing wall and what a spectacle they make! Moyesii, Kew rambler and Brenda Colvin have scaled a 6 metre wall in less than 5 years.

And Paul’s Himalayan Musk has rewarded deep fertile soil and the right level of sun by scrambling into the garden beyond. Mine has an equally thuggish tendency with much poorer soil and a Scottish sun.

Both Daniela and Magdalen manage the roses strategically. Although late summer pruning produces the best flowering stems for the following year, you lose the autumn hips. So the best compromise is to prune some stems after flowering and leave the rest for an autumn show.

In the formal gardens, weeping standards play an important part. I can’t stand our predictably boring flowering tennis balls grafted on deadly bare stems. But skilfully pruned weeping standards are altogether different.

Surprisingly, vigorous ramblers are used for this, so you could feature a top grafted and duly tamed one in a pocket-sized garden. Their pliable, lax stems weep almost to the ground, completely concealing unsightly stems.

Daniela assures me that, when pruning, ‘you can’t cut enough, the rose is stronger than before.’ Society volunteers prune the standards in March and April, ruthlessly cutting the previous year’s growth to above the graft. As Daniela showed me, failing to completely cut back leaves unsightly stumps that couldn’t be rectified.

One of the first roses planted this way in 1983 was a Venusta pendula. With the trunk now about 10cm in diameter and an abundance of vigorous stems growing from the crown, it produces a mass of semi-double white flowers flushed with pink at the margins of the petals.

Paul Noël, with strong but pliable stems, is equally good. There are several recently planted examples and a fine old specimen occupied a corner.

Plant of the week

Strawberry ‘Vibrant’ carries its berries on strong upright stems, helping to keep them away from the earth. The delicious fruits ripen early.