Tonight, you’ll no doubt see neighbourhood children traipsing door-to-door in costume, shrieking and laughing along the way. You’ll see superheroes and scarecrows, pirates and police officers, wizards and witches. Some costumes go in and out of fashion; but there are witches every year.
There are witches in the woods, too.
The witches in the woods aren’t children in costume, and they aren’t the malevolent beings that inspire those costumes. Instead, they’re natural phenomena that for one reason or another we’ve given witchy names to. Three that are common where I live are witch-hazel, witches’ broom, and witches’ butter.
Witch-hazel, Hamamelis virginiana, is a large, broadleafed shrub common in moist, acid woods and thickets along riverbanks and lakeshores. In eastern North America, it’s one of the last plants to flower each year, flowering in September and October with its somewhat untidy sprays of tousled yellow petals. When they persist late enough in autumn, they sometimes wear bonnets of snow. Why “witch”- hazel? There are two possibilities. In Middle English, “wiche” meant “pliable”, and the young twigs and branches of wych-elm and witch-hazel are indeed easily bent. (The same root gives us the word “wicker”). In addition, the young branches of witch-hazel are favoured as dowsing rods in divining for water – a witchy sort of pursuit. It seems likely that “wiche” evolved to “witch” as a result of this use, or perhaps it was the other way around – perhaps the “wiche” name suggested use in divining. That witch-hazel sometimes persists in flower to Hallowe’en is a happy coincidence, to be sure, but it doesn’t seem to connect with the plant’s name.
Witches’ broom can refer to any number of cases in which a tree or shrub develops a tight, bushy growth of short twigs resembling the end of a broom. The growth of a witches’ broom can be triggered by a genetic mutation in one line of plant cells, by the attack of mistletoes (parasitic plants), by infestation with mites, or by infection with a number of microbial parasites. My favourite witches’ broom occurs on spruce, and results from infection by the rust fungus Chrysomyxa arctostaphyi (the “spruce broom rust”). These tightly-packed brooms turn yellow, then brown, as affected needles die – although only with multiple infections is there serious damage to the tree. I love spruce brooms because of their life cycle. The fungus alternates (as most rusts do) between two hosts, with the non-spruce host being bearberry or kinnikinnick (Arctostaphylos uva-ursi). On each host, the fungus produces asexual spores, which are carried by wind and can only infect the other host. On spruce, it also produces sexual spores, along with a sweetly putrid odour that attracts insects to carry those spores between individuals. This is the same system, with the same odour cues, that flowers use in attracting insects for pollination.
Finally, the oddest name: witches’ butter (Tremella mesenterica, and related fungi). This is a small, yellow or orange fungus with a lobed, convoluted body (hence another common name, “yellow brain”). Most individuals are small, perhaps a centimeter or two, and when fresh they have a rather gelatinous texture. They grow on dead wood, and for years I assumed that they were decomposers. It turns out I was wrong. Instead, they’re parasites of other fungi, and it’s their hosts that are decomposers (unseen within the wood). Despite “gelatinous”, “brain”, “dead wood”, and “parasite”, though, witches’ butter is beautiful: especially on a cloudy day, it provides a splash of sunny colour on a brown forest floor. But why “witches’ butter”? Butter from the yellow, of course; but witches? Some sources suggest a folk belief that one could defend oneself from witchcraft by throwing witches’ butter onto a blazing fire (certainly an improvement over burning the witch herself). A better story: because the fungi can appear rather suddenly, a Swedish folk myth holds that witches’ butter is formed when witches come in the night, milk a household’s cows, and scatter the butter on the ground.
Hazel, broom, and butter: three witches in our woods. Wonderful!
© Stephen Heard (email@example.com) October 31, 2017 but licensed CC BY-NC 4.0
Note: This is a science outreach piece belonging to a series I wrote for the newsletter of the Fredericton Botanic Garden. I’d be happy to see it modified for use elsewhere. If you use it, though, I’d appreciate hearing where and how.
Other Botanic Garden newsletter outreach pieces:
- The biology of plant galls
- Nature’s pharmacy? Medicinal plants in the Garden
- Why goldenrods don’t make you sneeze: the biology of pollination
- How plants prepare for winter
- What’s in a (Latin) name?
- Spring, light, and strategy on the forest floor
- The garden of insects
- There’s fungus among us
- Life under the snow
- The botany of henna
- Why is our Garden green?