As I write this in mid July, Hypericum perforatum has been in flower for several weeks, in gardens and on roadside verges. It gets its specific name from the appearance of its leaves. A leaf held up to the sun appears to be dotted with tiny perforations. They are in fact pockets of transparent oil. And why St John’s Wort? Richard Mabey tells us that it was one of the sun herbs, burned on Midsummer’s Day as part of the pagan purification ceremonies to enhance the power of the sun in purifying communities and crops. With the advent of Christianity, the plant was adopted for St John, since the feast of St John the Baptist is on June 24, conveniently close to Midsummer’s day.

Over the last ten years Hypericum perforatum has become a popular remedy for mild to moderate depression. Herbalists have always used it for this purpose and for many other conditions. Its efficacy in depression is supported by the results of many clinical trials. A recently published meta-analysis of 13 such trials found extracts of the herb to be as effective as selective serotonin uptake inhibitors (SSRIs) in the treatment of mild to moderate depression. It also found a similar incidence of side effects associated with the two treatments. However, patients taking St John’s Wort were less likely to withdraw from a clinical trial as a result of side-effects than patients taking SSRIs, suggesting that the side-effects from the herbal remedy were less troubling.

One of the most useful items in the herbal dispensary is infused oil made from this plant. It is made by steeping the yellow flowers in a jar of oil (olive, almond or sunflower oils are all suitable) placed in direct sunlight for several weeks. The oil will turn a deep red as the constituents of the flowers are extracted. The oil is then strained off the flowers and used in a variety of external applications. It has an antiinflammatory action and is also effective against enveloped viruses, including those of the Herpes group. Thus it can be usefully applied to burns, insect bites, cold sores and the lesions caused by Herpes zoster (Shingles). It is often included in creams to treat eczema.