Every gardener and allotmenteer knows the therapeutic effects of a few hours on the plot or tending to the flower border – even if a pest has struck the broccoli or the lilies, it is still one of the most relaxing things you can do. But last summer I left Plot 35a for the day and went to visit the horticultural charity Thrive at their garden in Battersea, south London, where gardening therapy is a full-time, serious concern.

Gardening can be issued as a prescription, just like physiotherapy after a road accident or sporting injury, or antibiotics for an infection. Gardeners like Richard, whom I met on a beautiful sunny day in July, help Thrive’s patients/clients with growing and rehabilitation. There is already scientific evidence showing that the act of gardening relieves stress and helps physical fitness. Thrive does this and more: the charity helps people with disabilities, those struck by ill health or who are isolated or vulnerable. Thrive has a number of gardens around the country, but at Battersea, as Alyson from the charity told me, they also have tailored programmes for stroke patients, young people with special needs as well as the unemployed.

The Old English Garden, one of the secret idylls that Thrive uses in its work, was designed by Chelsea gold medal winner Sarah Price and funded by the luxury fragrance brand Jo Malone Ltd. There are colourful borders of roses, lilies and violets, statuesque angelica and kniphofia, and, when I went, a pomegranate plant drinking in the London sun.

The Herb Garden next-door is more productive – and has more than just herbs in its beds. It is more like a market garden, with a huge Alitex greenhouse at one end. Richard, who is Thrive’s longest-serving member of staff, showed me the different sections that the Herb Garden is divided into: a productive vegetable garden, fruit trees, a section of global crops, including millet, maize and blood-red amaranth, medicinal and therapeutic plants, and a garden for women’s health.

The Herb Garden is partly funded by Boursin, the French cheese maker who know something about herbs. It was one of those sweltering days in the capital where London could be on the Mediterranean, or maybe I was carried away by the sight of this lavender underneath an olive tree.

At the time of my visit, Thrive was running a competition to search for a name for a specially selected new form of sweet pea to boost its fundraising – it was created by Thompson & Morgan, who hope to raise £10,000 for the charity through sales of the sweet pea seeds. It has delicate pink and white flowers and the winning name for the new variety was ‘Eleanore Udall’, in memory of the wife of Dr Geoffrey Udall who bequeathed his estate at Beech Hill near Reading to the charity.

I hope to grow some of this pretty variety in my allotment this spring. You can support Thrive’s work by buying some of these sweet peas for £2.99 a packet at www.thrive.org.uk