# Houseleek (Sempervivum tectorum)

**Sempervivum*; Jupiter’s beard*

**Known today as.** *Sempervivum tectorum*.

Kind: Plant  
Qualities: Cold and moist (Galenic tradition).

## What was it used for?

Cooling: its juice for burns, inflammations, and hot fevers.

## What does modern science say?

A soothing juice; no specific action shown.

## Pharmacognosy and toxicology

- **malic and isocitric acids**: the sour juice
- **mucilage**: 
- **kaempferol glycosides**: 
- **tannins**: 

**Mechanism.** The leaf juice is cooling as aloe gel is, by water, mucilage, and mild acidity, which soothes a burn; it is astringent enough to help a small cut. Nothing in it enters the body.

**Dose.** Safe on the skin; the juice is a weak emetic swallowed.

**Standing.** No monograph; a plant of folk first aid, kept on roofs by Charlemagne’s capitulary against lightning.

## What lore surrounds it?

Grown on roofs to ward off lightning and fire.

## What did the older authorities say?

**Charlemagne.** The *Capitulare de villis* ends by ordering that every gardener have “Jupiter’s beard” growing on his house.

## Sources

- *Capitulare de villis* (c. 800).
- Alberti, Á., et al. (2012). “Characterization of phenolic compounds and antinociceptive activity of *Sempervivum tectorum* L. leaf juice.” *Journal of Pharmaceutical and Biomedical Analysis* 70.

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*Houseleek.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-09-25. The Thinking Press. https://thethinkingpress.org/materia-medica/houseleek

Historical description, not medical advice.