Archive, Hazardous plants, Herbal medicine, Poisonous Plants

Foraging St John’s wort

Hypericum perforatum  (St Johns wort)

Hypericaceae family

This summer-flowering medicinal plant grows wild and free throughout many areas of Britain. With a liking of numerous settings it will be easy for foragers to find St John’s wort, and with unique observable characteristics, it is simple to identify. You can find out more about plant identification on my foraging walks and courses.

The scientific name for the genus, Hypericum, is thought to originate from the two Greek words – hyper, meaning above, and eikon, meaning ‘picture’.

The bright yellow flowers, which many centuries ago were felt to be symbolic of the sun, or spirit, were placed above religious pictures, specifically St John, to help ward off evil spirits during the celebrations of the midsummer Christian festival. Church leaders placed their festival onto the ancient summer solstice festivities (since the introduction of the Gregorian calendar, this has traditionally been celebrated on 24th June, previously falling on or around the 5th July).

The extractable red flower oil was previously meant to symbolize the blood of St. John. The species name perforatum is derived from the Latin word meaning perforated. Visible translucent perforations on both the leaves and the petals are visible with the naked eye.

The blood red stems of young spring growth on Hypericum perforatum.

Botanical description of St John’s wort

St Johns wort is a native British perennial, from a genus containing over 400 species of annuals, herbaceous perennials; deciduous, semi-evergreen and evergreen shrubs and trees. This plant grows throughout Europe.

St Johns wort is a clump-forming perennial which can grow to a height of up to 90 cm in flower. Re-appearing each year from its crown, it produces numerous red stems that eventually branch towards their upper parts. The stems bear small and hairless leaves, which are opposite and mostly oblong, but always sessile. The leaves typically grow to 3-4 cm long.

If you hold the stems up to the light, close inspection will reveal the leaves have numerous translucent glands, as well as a few dark ones at the edges on the undersides. The lanceolate petals and shorter sepals in the flower are also marked with dark dots.

The presence of the dark oil bearing glands, as well as the slight, opposite ridges on its round stem are crucial identification factors between this and one of more than half a dozen other Hypericum species that populate Britain.

The bright, glossy yellow flowers are similar in size to a buttercup. They have five petals and are borne on a corymb inflorescence. These types of flowering displays are often referred to as umbel-like.

When in full display, the shiny, showy blooms are noticeable for having more than fifty stamens spraying out from the centre of the flower. These are fused in the lower part into three bundles.

Hypericum perforatum flowers

Flowering Period

The flowering period for this plant is usually lengthy, and occurs between June and September, with the seeds ripening from late July to October. The self-fertile flowers are pollinated by bees and flies.

Soils and Habitats

St Johns wort absolutely delights on calcareous (alkaline) soils, as will be seen by the propensity of it when visiting chalk grasslands such as around Winchester and in West Sussex on the South Downs. It’s not a completely fussy plant, so will also be found on mildly acidic ground.

It can do well on waste-ground and some woodland edges, and is often seen happily populating pastures, as well as roadsides and occasional hedges. This is a lowland plant, so will be found at maximum altitudes up to around 480 metres.

St Johns wort can grow in the semi-shade of light woodland, or will be even more happy in full sun. The large tap-root helps it to flower right through the summer, even during periods of drought.

Although the plant can set viable seed, regeneration also occurs through its creeping lateral runners, arising at various points on the rootstock.

Parts used Leaves, flowers.

Harvest In summer (Flowers only for an infused oil).

Key constituents Hypericin; pseudohypericin; flavonoids (including hyperforin, kaempferol, luteolin, quercetin, rutin); phenolic acids (including caffeic acid, ferulic acid, chlorogenic acid); xanthones; mono-amine-oxidase-inhibitors (MAOIs).

Actions Anti-depressant, anti-viral, anti-bacterial, anti-inflammatory, mild astringent.

Pharmacology and uses The chemical composition of St. John’s wort has been well studied, especially in the last thirty years. Documented pharmacological activities include anti-depressant, anti-viral, and anti-bacterial effects. These provide supporting evidence for several of the traditional uses stated for St John’s wort.

In terms of the recent history of British herbal healthcare, St Johns wort has had a somewhat meteoric rise to prominence. Many of its pharmacological activities remain unclear, although a number of actions have reportedly been attributable to hypericin and the flavonoid constituents.

Evidence from a number of randomised controlled trials during the 1990s, highlighted and confirmed the efficacy of St John’s wort extracts over placebo’s, in the treatment of mild-to-moderately severe depression.

St. Johns wort and extracts of it have been shown to be effective against short-to-medium term mild depression, but not long-term or severe depression. As with a lot of plant medicines, there is a need to further assess the efficacy of St. Johns wort, compared with that of standard anti-depressants.

Although the anti-depressant actions of this plant were only elucidated during the last 40 years or so, this plant had an acknowledged ability throughout history to relieve melancholy, as was noted by Gerard in his Herbal (published 1597). Folk medicine records also show many lay-people knew of its power to cure nervousness and low spirits, so it was also used it as a general tonic.

St John’s wort and mono amine oxidase inhibitors

St Johns wort contains molecules known as MAOI (mono-amine oxidase inhibitors). As their name suggests, the MAOI action is an inhibiting one. These molecules are known to increase the availability of mono-amine neuro-transmitters such as serotonin in the brain (thereby helping to combat feelings of depression). This plant is known to increase deep sleep and can be useful in cases of insomnia. 

Hypericin – a weak MAOI, but exerting effect on other neurotransmitter sites.

Interestingly though, the MAOI in this plant are weak and have been shown not to be responsible for the anti-depressant effect of St. Johns wort! However, what scientists do know about hypericin and the flavonoids are that they exert a number of effects on both the GABA (Gamma Amino Butyric Acid) and Glutamate receptor sites in the brain. These neurotransmitters are directly involved are in feelings of well being and in helping our central nervous system relax.

A number of concerns have been raised by allopathic practitioners over possible dangerous interactions between St John’s wort and certain prescribed medicines (including warfarin, ciclosporin, theophylline, digoxin, HIV protease inhibitors, anti-convulsants, selective serotonin re-uptake inhibitors (SSRI’s), ‘triptans’ and oral contraceptives).

Medical advice in Britain and America usually states that patients taking the aforementioned medicines should not take, or stop taking St John’s wort! Before embarking on a course of St Johns wort, and especially when on other medication, you need to seek advice from a pharmacist or another healthcare professional with detailed knowledge about these potentially dangerous adverse interactions!

Concentrating on the anti-depressant substances in St Johns wort could detract somewhat from the many other traditional applications for which this plant has been used.

Interestingly, a book by Gabrielle Hatfield and David E Allen, titled ‘Medicinal Plants in Folk Tradition – An Ethnobotany of Britain and Ireland’, which was published almost 10 years ago, suggests that the reputation St. Johns wort has for healing cuts, grazes, and more serious wounds and burns, is likely to be more attributable to all of the Hypericum species found in Britain, rather than the one species under discussion in this monograph.

A different Hypericum species on a limestone cliff in the Gower, south Wales

Moreover, St John’s wort is a name given to more than one Hypericum species, and judging by maps of the British flora, H.perforatum won’t be found in all the areas that records of ‘St Johns wort’ use has been documented.

In their fascinating book, pieced together using information from before mass public travel and transportation, and sourced notably from unconnected areas of the UK and the Isle of Man, the authors report that various Hypericum species have been used, and seemingly with much effect.

St Johns wort oil has long been known of, for its topical pain relieving and soothing action on burns and scalds, ulcers, inflammations, and various forms of muscular pain.

Tutsan – Hypericum androsaemum. Likely to have been used medicinally in lieu of St Johns wort.

The red-coloured infused oil, extractable from the petals, has been used for these and other related complaints. St Johns wort can be usefully employed to treat conditions such as neuralgia, fibrositis, sciatica, excitability, anxiety, and as a general nerve tonic.

St Johns wort also aids the regeneration of granular tissue during healing of wounds. Indeed, Nicolas Culpeper, described in the 1640’s that it was “a singular wound herb” and that “it closes up the lips of wounds”.

Today, St Johns wort is a well known species and one of our most widely used herbal remedies. Contemporary uses have built on the fragments of traditional folklore collated from these islands. It is one of the staples of any Materia Medica here in Britain, and due to it being so common, one you can easily harvest, process and store each summer.

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