Monday, June 10, 2013

Plant Story: Common Houseleek, Sempervivum tectorum, Folklore

Sempervivum tectorum, hens-and-chickens
Sempervivum tectorum, hens-and-chickens, aka Jupiter's  beard
stonecrop family, Crassulaceae
   One widely-planted succulent (see previous post) is the plant I grew up calling hens-and-chickens Sempervivum tectorum (Crassulaceae, stonecrop family). These days the preferred common name seems to be houseleek. There are 34 genera and 1,400 species in the Crassulaceae, with 30 species of Sempervivum and hundreds of Sempervivum hybrids and cultivated varieties. Sempervivum tectorum thus gets called the common houseleek, since you might want to call all the other sempervivums houseleeks too. 

   Native to Europe, the common houseleek has been grown in and around human settlements for millennia. Like many plants that are familiar to a lot of people, it has many common names. Frequently used in the U.S. are hens-and-chickens and common houseleek. More obscure common names are Aaron's rod, bullocks eye, Jupiter's beard, Thor's beard, syngreen, and a half dozen more (see Wikipedia entry).

Sempervivum tectorum rosette -  note thickness of leaf
Sempervivum tectorum rosette -
note thickness of leaf I broke
   The scientific name, Sempervivum, means "live forever" (semper = always, vivum = living), as does the common name syngreen and its variants. This doubtless refers to the fact that uprooted plants can survive for weeks, living on their stored water. Pluck up a pansy (Viola tricolor) or a dandelion (Taraxacum officinale), with or without roots, and in hours they are wilted and in a day or two, dead. Do the same thing to a rosette of hens-and-chickens, and more than a week later you can stick it back in  moist soil and it will recover. Try it!
This is the benefit of storing water the way a succulent does.

   The hens-and-chickens common name follows from the growth form, where little clones are grow around the initial plant. (See picture below, but I don't have a really classic photo of hen with chickens.)

hens-and-chickens in rock garden in Colorado
hens-and-chickens in
rock garden in Colorado
    The tectorum in Sempervivum tectorum and the English names Jupiter's beard, Thor's beard and houseleek all refer to the plant's long association with lightning.

     This is a story that seems very odd to us in the modern world.

     First, the plant was called Jupiter's beard in the ancient Rome, Iovis barbam. As I understand it, most Roman men were clean-shaven. Jupiter, king of the gods and king of the sky, was routinely pictured with a beard. The round shape of Sempervivum tectorum, native to the Alps and the Pyrenees, reminded Romans of the face of Jupiter (images at Google). From that, somehow, came the belief that the plant, Jupiter's beard, would protect you from the lightning cast by Jupiter. Perhaps that was because the plant was associated with Jupiter, perhaps because it was moist and succulent.

     Lightning strikes were as frightening to Romans as they are today. In fact, they were perhaps more frightening since lightning was a completely mysterious force. There was no explanation linking lightning to anything familiar to Romans. Consider that electricity was unknown to science until the 1700s, and an obscure scientific curiousity until after Edison made electric light practical (1880s). In classical Rome, an inexplicable force from the sky struck your house and the house burned to the ground before your neighbors could organize a bucket-brigade from the creek.

sod-roofed house (botanical garden, Reykjavik, Iceland)
sod-roofed house (botanical garden, Reykjavik, Iceland)
    This probably led to a variety of superstitious practices now lost to history. Planting Sempervivum tectorum on the roof to ward off lightning, however, was definitely a Roman response to the threat of lightning. That is easier to comprehend if you imagine sod or thatched roofs in Europe, rather than modern shingled roofs.

   Planting on roofs is the origin on the species name, tectorum, which translates to "of roofs." It is believed to also be the origin of the name houseleek. Houseleek means "house plant." Leek, and spelling variants such as leac, is an old Anglo-Saxon word for plant, most often used for garlic (garlaec) and its relatives. Thus, houseleek is the plant on the house. (Before the development of clear glass windows, in 17th century, plants could not grow indoors so our current use of the term house plant, a plant grown inside the house, is from after the advent of glass windows.) People believed houseleeks on the roof would protect them from lightning. Likewise they believed houseleeks would protect the house from fire. It does seem reasonable that the succulent leaves might well not catch fire as easily as, say, grasses on the roof.

   This practice was preserved for historians when Charlemagne (720-814), first Holy Roman Emperor and unifier of a large part of northern Europe, ordered that all villagers within his crown lands plant houseleeks on their roofs, presumably as a safety measure. He decreed: Et ille hortulanus habeat super domum suam Iovis barbam. (And the gardener shall have house-leeks growing on his house. Capitulare de villis, about 795,  LXX.) Note Charlemagne actually used the name Jove's--Jupiter's--beard.

    The plant also has Thor's beard as an English common name. That would have been a reasonable name to have been used by the pagan Germanic tribes with whom Charlemagne interacted, although I don't actually find it in late medieval English herbals (Culpeper, Gerard, Hill, see sources below). Our English days of the week--Thursday, Thor's day--come from the names of the gods of the Germanic Anglo-Saxon tribes who settled in England beginning in the 5th century. Charlemagne fought Germanic pagans--in his time the Scandinavians were still staying at home. Charlemagne is famous for forcible conversion of pagans to Christianity (see, for example, Wikipedia on Charlemagne: Saxon Wars).

    However, you can read on the internet that the houseleek was "sacred to the Norse god Thor," often with the implication that Charlemagne learned that houseleeks protect from lightning from the Vikings, for example:  "Thus, Thor’s plant became House Leek (Plant) and a Scandinavian myth became a royal edict for all Europe to observe."Roots of Wisdom  This, I think, is inaccurate. 

   First, the botany doesn't fit. The common houseleek, Sempervivum tectorum, is native to the Alps and the Pyrenees, not Scandinavia. It is not hardy in much of northern Europe--conditions are too cold and wet. It does not survive in Ireland, Iceland or the Faroes at all. Sempervivum tectorum is not native to England, although it was introduced "in ancient times" (perhaps by the Romans, perhaps by the Anglo-Saxons). In Norway, it only survives along the southern coast. Scandinavians of the Viking Era had quite different political boundaries than we do now--southern Norway and western Sweden were often part of Denmark--but from there they dominated the north Atlantic and settled from Moscow to Newfoundland, and, in 911, in Normandy. The fact that Sempervivum tectorum is not native to that area and will not grow except at the southern edge of it, suggests that pagan Scandinavians may not have known the common houseleek, let alone used it much.

common houseleek, Sempervivum tectorum
common houseleek, Sempervivum tectorum
        Rolf Nordhagan (see references below) showed that Norwegians used the same common name for sedums, in particular Sedum maximum, as for Sempervivum tectorum. Thus, he believed the reports of houseleeks in Norway, for example on roofs in medieval Bergen, refer to Sedum not Sempervivum. Both are succulents in the plant family Crassulaceae, and, although they seem pretty different to me (see photos online: Sedum maximum), they are frequently confused in the old European literature. For example, Culpeper in 1652 calls three sedums, Sedum minus, S. minus haematodes and S. acre by the English name houseleek. The report of houseleeks on roofs in Bergen was in the 1200s, well into the Christian era, and so no matter which plant it is, it doesn't support Sempervivum tectorum being sacred to the Norse pagan god Thor.

     Note also that of all the Norwegian common names Nordhagan gives for houseleeks (see reference), including variants of syngreen, thunder plant and Jupiter's beard, there is no Thor's beard or variants that include the name Thor.

    In addition, the timing is off. Charlemagne lived before the Viking Era (late 8th century to the late 11th century). The first Viking raid on what is now France was in 845. Charlemagne's sons and grandsons were the kings of the Franks who were plagued by Viking raids. Chronologically, it is more likely that Vikings or Norse could have gotten houseleeks from Charlemagne than vice versa.

    Thus it seems to me that the association of houseleeks with lightning began in southern Europe and moved north rather than it was borrowed from the Norse. And probably the Thor after whom Thor's beard was named was Germanic not Scandinavian--if it wasn't a post-medieval name entirely.

    There are gaps in my argument, but the common houseleek is native to central not northern Europe and not hardy very far north, the Romans knew Sempervivum tectorum and grew itand before the Viking Era, Charlemagne ordered it to be used on roofs.
common houseleek, Sempervivum tectorum
common houseleek, Sempervivum tectorum
     Late spring is the beginning of the fire season in the western United States. This weekend was the first anniversary of the largest wild fires in the history of Colorado. With that in mind, the Denver Post ran an article by Susan Clotfelter that gave suggestions for fire-proofing one's property (link).  She suggested planting fire-wise plants such as sedums, echinacea and flax. I would add common houseleeks to that group, at least for historical interest.

Comments and corrections welcomed!

My Sources: 
Bosworth, J. An Anglo-Saxon Dictionary Online. Leác. Ed. Thomas Northcote Toller and Others. Comp. Sean Christ and   Ondřej Tichý. Faculty of Arts, Charles University in Prague, 21 Mar. 2010. Web. 7 June 2013. 
Coombes, A. J. 1985. Dictionary of plant names. Timber Press, Portland, OR.
Culpeper, N. 1652. Culpeper's complete herbal.'s_complete_herbal
Gerarde, J. 1597. The herball or generall historie of plantes. online K. Stuber. 2007. Wageningen UR Library.
Grieve, M. 1971 (originally 1931). A modern herbal. Dover Publications, NY.
Hill, T. 1987. The gardener's labyrinth. The first English gardening book. 1577. Oxford University Press, Oxford. 
Kelaidis, G. M. 2008. Hardy succulents. Storey Publishing, North Adams, MA
Lust, J. 1974. The Herb Book. Bantam Books, NY.
Nordhagen, R. 1985. Houseleek and stonecrop. The Sempervivum Society Journal. 16 (1) x-22; 16 (2) 40-44/
Sawyer, P. ed. 1997. The Oxford illustrated history of the Vikings. Oxford University Press, Oxford.
Schneider, R. ed. Capitulare de villis.

Buy the Book! Give it as a gift! This story and thirteen other plants from around the world are told in Curious Stories of Familiar Plants from Around the World. Available on Amazon link,

Kathy Keeler, A Wandering Botanist
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