Our gardening correspondent Ruth Pavey has for years explored the gardens of the Ham&High community. This week, she finds a Hampstead Garden Suburb resident making a big impression in the National Gardens Scheme’s Yellow Book

One of the criteria for inclusion in the National Gardens Scheme (NGS) Yellow Book is that your garden should contain enough of interest to detain a visitor for more than a few moments. As many London gardens are small, this means that intense planting, of which Yvonne Oliver is a prime exponent, works well.

Into the relatively small plots, front and back, of her cottage in Hampstead Garden Suburb she fits not only a wealth of plants but also sculptures, some made by her husband, found objects, a pond, a cactus cabinet, a small greenhouse, birdbaths and a bench with a long history.

To fit a lot into a small area it helps to think vertically. This suits Yvonne, as she loves clematis and grows many of them. Several beautiful ones in flower when I visited should still be flourishing in late July, including “Etoile Violette”, “Perle d’Azur” and “Prince Charles”. “Black Prince” and “Royal Velours” should also be flowering by then.

Yvonne labels them in an attractive way, writing their names on oyster shells attached at eye level to whatever they are growing up; trellis, obelisk or pergola. Dividing the garden up with these tall structures gives the impression that the space is greater than it actually is.

On the back wall of the house there are vertical pot-holders, another device for increasing planting space. It also increases the need for watering – this is not a low maintenance garden.

A developing interest in later summer flowering plants goes with Yvonne’s decision to open for the NGS in July rather than June this year. Heleniums, veronicastrums, thalictrums, echinacea, salvias and eupatoriums are all there awaiting their moment, so tall and tightly packed Yvonne says she doesn’t have to worry about weeding, the weeds don’t get a chance.

Grasses and ferns are among Yvonne’s other enthusiasms, with campanulas beginning to beckon.

As with many plant lovers, Yvonne has particular nurseries she favours, among them Bodmin Plant and Herb Nursery and Pinsla Nursery, near Bodmin.

Nearer to home, she also recommends Glebe Nursery in Enfield, but they mainly serve the trade and are not set up for retail customers – although the owner did tell me that the occasional retail customer does not get sent away.

Wine box

As I know that Yvonne is good with cacti I had arranged to bring her a few specimens that, living with me, have long been dejected. She and her husband received this offering in what may be a characteristic manner – the plants were welcomed in but it was the box, a wooden wine box, that sparked their interest. I happen to have a good source for such boxes and was delighted to leave it with them, confident that it will soon fit in among the old sewing table with marble top, the planted-up sinks and other old boxes that make up such an attractive array at the back of their house.

Last year, The London Gardens Society awarded Yvonne the top award in its small back garden category and a bronze for the front. These gave her the highest individual points, therefore the Banksian Medal. She is awaiting the results for this year.

Diane Berger, her fellow Hampstead Garden Suburb Horticultural Society member, is opening her dazzling garden on the same day as Yvonne, on Sunday.

The openings are separately ticketed, but the important thing to know, says Yvonne, is that teas will be served at Diane’s.

Yvonne’s garden at 4 Asmun’s Hill, NW11, will be open on Sunday, from 1pm to 6pm, as will Diane Berger’s at 86 Willifield Way, NW11.