St. John's Wort

A prescription that suddenly seems less effective after starting a supplement - breakthrough bleeding on a contraceptive, an INR that will not settle, rising viral load, transplant rejection markers. Agitation, sweating, tremor, fast heartbeat or confusion after combining it with an antidepressant, a triptan or tramadol, which needs urgent medical attention. Increased sunburn on fair skin at higher doses.

This is a medical matter, not a garden one. Do not stop a prescription because of an interaction - contact the prescriber, who can adjust monitoring or dosing while the enzyme effect washes out over one to two weeks. Suspected serotonin syndrome is an emergency: seek immediate care. Nothing on this page substitutes for a clinician's advice.

Tell your prescriber and your pharmacist before you take it and before you stop it, and treat it as a drug rather than a tea. Do not add it on top of a prescribed antidepressant, and do not swap one for the other yourself. Anyone on a contraceptive, an anticoagulant, a transplant medicine, an HIV medicine, an antiarrhythmic or cancer treatment should treat this as a conversation to have before the first dose. Home-made preparations have no dose control at all.

St. John's wort is the textbook herb-drug interaction. It induces the liver enzyme CYP3A4 and the drug transporter P-glycoprotein, which between them handle a large share of all prescription medicines, so the body clears those medicines faster than the prescribed dose assumes and they stop working. Documented consequences include contraceptive failure with breakthrough bleeding and unplanned pregnancy, loss of anticoagulant control on warfarin, organ rejection in transplant patients on ciclosporin or tacrolimus, and loss of viral suppression on HIV antiretrovirals. Digoxin, some statins and several cancer drugs are also affected. Separately, combined with SSRIs, SNRIs, triptans or tramadol it can contribute to serotonin syndrome. The effect builds over one to two weeks and fades over a similar period, so stopping matters as much as starting.

A clump thickening outward with new shoots a few inches beyond the old crown. New patches appearing at gateways, along tracks, downslope and wherever soil or hay has been moved. Rusty capsule heads and reddening foliage in late summer, which is the easiest time to see the true extent of a stand. Seedlings reappearing on ground cleared several seasons ago.

Dig small clumps whole in moist soil, taking the woody crown and the lateral runners, then remove every resprout for the rest of the season. On larger infestations, systemic herbicide timed to bud and early bloom, or to autumn regrowth, is the practical tool - use a product whose label lists the site and follow that label, including grazing and haying restrictions. Where the introduced Chrysolina leaf beetles are active, leave them to work. Reseed cleared ground with competitive grasses, and plan on checking the same ground for several years.

Do not plant it, and do not move it. Clean boots, tires, mower decks and machinery before leaving an infested area, and do not move soil or hay from infested to clean ground. Keep pasture dense and avoid overgrazing, because it establishes on bare disturbed soil and struggles against thick competition. Cut stands at full bloom so they cannot seed while you plan the longer job.

The reason it is a listed noxious weed across much of the West. It runs two ways at once: a woody crown pushes out short lateral runners so a single plant thickens into a patch and regrows from any crown or runner fragment, while a mature plant sets thousands of tiny seeds that are sticky when wet and stay viable in the soil for ten years or more. It colonises bare, disturbed, logged and overgrazed ground, displaces forage grasses, and at its historic peak covered millions of acres of northern California and Pacific Northwest rangeland. Because the seed bank outlasts almost any control programme, a patch that looks clean after one good season is not clean.

Reddened, swollen, weeping or peeling skin on white faces, pink muzzles, ears, eyelids and udders while pigmented areas stay normal. Animals crowding into shade, restless or rubbing, off feed, dropping condition and milk yield. Damage showing up in animals fed hay from an infested field, with no plant visible in their pasture.

Move affected animals out of the sun and off the infested ground immediately, and call a vet - severe photosensitisation is painful, prone to infection, and can kill. Provide shade and clean water, and keep animals off the stand until it has been controlled. Do not feed hay from an infested field to pale-skinned stock.

Keep the plant out of pasture and hay ground: cut stands at full bloom so they cannot seed, treat or remove infestations, and keep the sward dense, since the plant colonises overgrazed and bare ground. Do not turn pale-skinned stock onto a heavily infested paddock, particularly in bright weather when the young growth is most palatable. Check hay ground before cutting.

The hypericin that stains your fingers red when you crush a bud is a photodynamic pigment. Animals that graze the plant absorb it, and it reacts with sunlight in the skin, so any area with little pigment or thin cover burns severely from the inside out. Sheep, cattle, goats and horses are all affected, and pale-skinned or white-faced animals suffer most: white faces, pink muzzles, ears, eyelids and udders blister, weep, swell and peel. Affected stock become restless, seek shade, go off feed and lose condition, and severe cases can be fatal. This is a real economic reason the plant was fought so hard on western rangeland - and hay cut from an infested field carries the compound with it.