What is Wood cranesbill?

Wood cranesbill is a wild meadow flower of northern Europe, used in Nordic folk medicine as a drying, tightening remedy for loose bowels and sore mouths. Its botanical name is Geranium sylvaticum. Norwegians call it skogstorkenebb; Finns call it metsäkurjenpolvi.

It grows in damp meadows, open woods and road verges, with violet-blue flowers in early summer. The root and the leafy parts were the pieces used. Both are rich in tannins, plant compounds with a dry, puckering taste.

Here is the honest verdict. No human trials of this plant have been published, so nothing about its effect in people is settled. Long traditional use is not proof that it works, and it is not proof that it is safe.

How does Wood cranesbill work?

Nobody has shown what wood cranesbill does inside the human body. The ideas below come from chemistry and laboratory work, not from people.

The plant is high in tannins. In test tubes, tannins bind to proteins and make wet tissue surfaces feel tighter and drier. That is the classic astringent effect, and it is the reason folk use focused on diarrhoea, mouth rinses and weeping skin.

Lab tests on Geranium tannins also report antioxidant activity. Some slow the growth of bacteria in a dish. Whether any of that happens in a person's gut, mouth or skin has not been established.

Tannins are poorly absorbed from the gut. So most of any action would stay inside the gut rather than reach the blood. That is a reasonable chemical guess, not a measured fact.

What forms does Wood cranesbill come in?

Wood cranesbill is rarely sold. Most use has been home-made from wild-picked plants.

Dry forms you may meet:

- Dried root, cut or powdered. - Dried leaf and stem for tea.

Prepared forms you may meet:

- A water infusion or decoction, drunk or used as a gargle or skin wash. - A tincture, meaning an alcohol extract, from small herbal makers. - A minor ingredient in mixed Nordic herbal blends.

There is no standard extract and no agreed strength. Wild material can be misidentified. Roadside plants can carry traffic grime or spray residue.

Where it comes from:

Scandinavian folk healers treated wood cranesbill as an astringent, a remedy that dries and tightens. Records come mainly from folklore collections of the 1700s to the early 1900s, not from medical files.

Reported uses included drinks for diarrhoea, gargles for sore mouths and throats, and washes for grazes and weeping skin. Some accounts mention it for heavy periods. Cattle healers used similar tannin plants for scouring livestock.

The petals were also used locally as a blue-violet dye. Across the Atlantic, a cousin plant, American cranesbill (Geranium maculatum), was listed in old US pharmacy books for the same astringent purpose.

These are claims that people made, written down by collectors. They tell you what was believed, not what was tested.

What does Wood cranesbill help with?

• Short-lived diarrhoea: This was the main folk use. Tannin-rich roots were simmered and the liquid was drunk. The reasoning is that tannins tighten the gut lining. That idea rests on test-tube chemistry, not on trials in people with diarrhoea. No study has tested wood cranesbill for this. Diarrhoea also usually settles on its own, which makes old reports of success hard to judge.
• Sore mouth, gums or throat (as a gargle or rinse): Folk use was a cooled tea, swilled and spat out. Astringent plants give an immediate dry, tight feeling in the mouth. That feeling is real and quick. Whether it speeds healing of a mouth ulcer or sore throat has not been shown for this plant. No human study exists. Related tannin herbs have weak and mixed evidence for the same purpose.
• Minor grazes and weeping skin (as a wash): A cooled decoction was used to bathe small wounds and oozing patches of skin. In laboratory tests, Geranium tannins slow the growth of some bacteria. Nobody has shown that this happens on human skin. Treat this as tradition only. A deep, dirty or spreading wound needs a nurse or doctor, not a plant wash.
• Heavy menstrual bleeding: Some Nordic accounts list astringent geraniums for heavy periods. The thinking was that a plant that dries tissue might also slow bleeding. There is no evidence for that in people, and no plausible route by which a poorly absorbed gut tannin would reach the womb lining. Heavy or changing periods deserve a medical check. Causes include fibroids, hormone problems and low iron.

What are the side effects of Wood cranesbill?

• Nausea or stomach ache, especially on an empty stomach
• Cramping or a griping feeling in the gut
• Constipation if used repeatedly
• A dry, puckering mouth and a bitter aftertaste
• Less iron absorbed from food, which can worsen low iron over time
• Skin rash or itch after contact with the plant, in rare cases
• Vomiting after a very strong brew

Good to know:

There is no safety study in people, so no one can say how common these effects are.

What is listed above is what tannin-rich plants do in general, plus what folk accounts mention. Most of it is mild and stops when you stop.

The quiet risk is iron. Regular tannin intake can tip someone who is already low in iron into anaemia, which means too few red blood cells.

How much Wood cranesbill should you take?

• Recommended daily: This page gives no amount, and here is why. No human study has tested any dose of wood cranesbill. It is not sold as a licensed medicine, so no label carries a tested figure. Tannin content varies hugely between roots, leaves, sites and seasons, so even a spoon measure means little. If you own a product that carries a maker's directions, those directions are the maker's opinion, not a tested dose. A pharmacist or doctor is the right person to ask before you use it.
• Best time of day: Time of day does not appear to matter. Spacing does. Tannins can bind medicines and iron in the gut. Keeping any tannin-rich tea a couple of hours away from tablets is the usual cautious habit.
• With or without food: There is a trade-off either way. On an empty stomach, strong tannins can cause nausea or cramping. With a meal, they bind more of the iron in that meal. A small amount of food is the usual compromise. If you have low iron, keep it away from iron-rich meals and ask your doctor first.
• Time to effect: The dry, puckering feel in the mouth is immediate. That is taste and touch, not healing. Any gut effect is unmeasured. It may be hours, and it may be nothing at all. Be ready for nothing to happen. With no trials, that is a fair expectation.
• How long to take it: No tested duration exists. Tannin remedies were traditionally used for days, not weeks. Two plain limits are worth knowing. Diarrhoea that lasts more than two days needs a doctor, not a longer course of herb. Steady tannin use over weeks can reduce how much iron your body takes up from food.