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The Monday Garden
The Mixed Blessing of Common St. Johnswort

Issue No. 121 - July 17, 2004
by Sue Sweeney

Common St. Johnswort is supposed to cure a whole bunch of things. Funny thing is that oil made from the flowers actually does work as a topical treatment for bruises, joint problems, and the like with an inflammation and/or neurological component. Also, many think that the herb helps with mild depression; scientists, though, aren’t absolutely certain how the herb affects the body chemically or even which chemical compound is the active one.
Picture: The "garden” form of St. Johnswort in my friend Karol’s garden; West Haven CT July 2004
What’s remarkable about Hypericum perforatum is that, outside of Europe, until very recently, government funds were more likely to be spent figuring out how to eradicate the herb from farmland than how to use it for medicine. In California, they imported a bug from Australia to eat it.
Common St Johnswort is a European-Mediterranean native that has been used medicinally at least since the Greeks started to keep written records. In the European Middle Ages, it was thought to protect against demons (a handy thing, today, if it’ll work for computers).

At some point, the herb got named for St. John the Baptist but no one, today, is sure why. In any case, the Europeans took Common St. Johnswort with them as they spread throughout the world, and it joyfully naturalized across the four remaining continents, mingling with its 60 or so local cousins.

Common St. Johnswort is a short, shrubby perennial that’s only too hardy and fast-spreading. It enthusiastically reproduces from seed and underground runners. It thrives in hot, dry, sunny places such as over-grazed fields. It’s particularly widespread in Western USA and Australia which have the extensive grazing land and the hot, dry summers that St. Johnswort adores.

picture: detail from Karol’s garden
You can tell most of the St. Johnswort family by the signature 5-petal; 5-sepal star-like flowers, with prominent center “tassels” (stamens). Locally, at the “kissing cousin” level, we have the several native St Johnsworts, mostly rare plants. There’s also an “ornamental” St. Johnswort garden hybrid. Shown in the pictures in this article, it’s more compact, and has more and larger flowers than the noxious weed/valuable herb variety. In North American gardens (Zone 5 or 6 to Zone 7 or 9, depending on the source), you might also see Aaronsbeard (Hypericum calycinum), a low, shrubby groundcover from Asia with typical St. Johnswort flower but they’re much larger. There are other North American cousins including a pink-flowered swamp plant.

You can tell Common St. Johnswort by the presence of dark dots that hold the red fluorescent pigment, hypericin. Hold a leaf up to the light and you’ll see translucent dots. Look for tiny black dots on the edge of the top side of the petals. There are also pairs of dots on the flattish stems. Crush the flowers and you’ll get blood-red hypericin juice, which will stain your fingers blue-violet.

The problem with Common St. Johnswort is that hypericin causes light-colored skin to become hypersensitive to sunlight. Most sources say that it primarily affects white-haired non-human mammals, primarily sheep, then cattle and horses, and, to a lesser extent, goats and pigs. Some sources do post a caution for humans and say that sensitivity is cumulative. The affected mammals don’t readily graze the herb but, if they’re hungry (e.g. forging on dry, over-grazed land) or it gets mixed in hay, consuming as much as 1% of body weight can be horrible for the animal. The animal can go blind, loose large patches of skin, and even starve to death. So you can see how Common St. Johnswort got on the noxious weed and invasive plant lists.

Many other members of the St. Johnswort family produce hypericin but apparently to a lesser degree. According to Purdue, the toxicity of the cousins has not yet been investigated, so handle all St. Johnsworts with care.

On the good side, it’s fairly well established that hypericin (or some other chemical in the plant - it has several active compounds) affects brain levels of dopamine and serotonin. Hence comes the feel-good affect. Hypericin (or whatever) also has antibacterial and antiviral properties, and is currently being investigated for treating everything from tuberculosis to HIV and herpes simplex. It’s my own experience that the oil mixed with arnica ointment is great for joint inflammation. (Even Stamford‘s Dr. Nicola Bott recommends it in the appropriate case.)

On the even-better side, since you can barely kill it, even with Australian bugs, it’s a very cheap, very available broad-spectrum medicine. Indeed, some sources say that it’s safe and easy to make your own oil from fresh flowers – check the web for recipes. Forget the AARP, think what this can mean to countries where the simplest drugs are beyond reach. (Do, though, use caution whenever self-medicating with herbs — “natural” doesn’t mean harmless! And, with Common St. Johnswort, do watch out for the possibility of hypersensitivity to sunlight and don’t grow it where it could endanger livestock.)

Last word: for the anti-chemical crusaders (like me): the more nitrogen you put on the growing herb, the less potent it becomes. So there!

From The Monday Garden. Copyright © by Sue Sweeney. Reproduced with permission. 

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