The back-garden pharmacy

St John’s wort (Hypericum perforatum)

What is it? Perennial with yellow flowers. It contains glycoside, thought to help increase production of the so-called happy hormones serotonin and dopamine - and the flowers contain hypericin, which has antiviral properties.

How does it help? It is used to treat mild depression.

How do I use it? Make an infusion using 25g of the herb in half a litre of water, and then take doses of 1 to 2 tablespoons. Or make an infusion of the flowers in olive oil to massage stiff joints. It's been shown to interfere with certain prescription drugs, so always check with your doctor. Ingesting the plant can cause sun sensitivity in some people.

What's the evidence? ‘Many well-designed trials attest to the effectiveness of St John's wort in reducing mild-to-moderate depression,' Dr Walker says. ‘Herbalists use it for a wide range of conditions, including menopause, sciatica and shingles. As it can interact with modern drugs it's always advisable to consult a herbal practitioner before taking it.' For a list of herbal practitioners, visit www.phytotherapists.org or www.nimh.org.uk.