A Christmas Herbarium: The Nature and Culture of our Favorite Holiday Plants

The Festive season is upon us. Many of us are busy hanging wreathes, decorating trees, and putting up mistletoe in doorways for that holiday smooch. If it’s Christmas you celebrate, most of our traditions go far further back than inflatable characters out of Rudolph the Red-Nosed Reindeer on the front lawn. And one thing that many of them have in common is that they involve bringing plants, or parts of plants, indoors. It makes sense. In winter, much of the color is gone outside, so those plants that stay green and have red berries very attractive at this time of year, especially for people whose homes where primarily gray stone and brown wood.

The practice of using red and green in celebration, according to some historians, dates to the Ancient Roman celebration of “Saturnalia”, which honored Saturn, the god of the sun and sowing. It occurred each year around December 17 and during it, Romans would decorate their homes with holly and exchange small figures made of wax, clay, stone or metal called sigillaria. (One unverified source says they were placed in the boughs of evergreen trees.) Over time, evergreen leaves and red berries, and then the colors themselves, came to symbolize the festive season.

Other plants are intimately associated with Christmas: holly, ivy, mistletoe, and poinsettia – and in most cases their life histories are closely linked to their cultural uses.

Christmas Tree – Evergreen trees – conifers – are distinctive for having needles rather than leaves. are the solution for a short growing season. They are gymnosperms, meaning that their seeds aren’t protected by a fruiting body. They’re an ancient lineage, first evolving on Earth sometime in the Paleozoic era, during the middle Devonian period about 390 million years ago. The Permian period was dry compared to the fern-covered periods that went before it, and needles were an adaptation that allowed conifers to carry out photosynthesis whenever the conditions are favorable. By not having to form new leaves in the spring conifers get a head start on photosynthesis and can continue into the autumn long after the deciduous trees have lost their leaves. Also, by not shedding their leaves every year, conifers are able to conserve scarce soil nutrients, which are often limited in sub-Arctic forests, because cold temperatures slow decomposition and nutrient cycling.

To the Ancient Saxons, trees and groves held sacred meaning. An Irminsul (Old Saxon meaning ‘great pillar’) was a sacred tree trunk erected in the open air that played an important role in Germanic paganism. The Yggdrasil was an immense ash tree was is central to their cosmology. They celebrated Jól, (or Yule), for 12 days from the winter solstice (21^st December). The evergreen trees of the Scandinavian forests, which looked healthy and green in winter compared to other plants, were a potent symbol of life. Scandinavians used to decorate evergreen trees with statues, food, clothing, and runes as tribute to the gods. It was believed that spirits living in the trees, but went away during the winter months, but could be coaxed back with household offerings. The modern Christmas tree, decorated with ornaments and candles, is said to have originated in Germany in the 16th-century with links to the protestant reformer Martin Luther. However, the first evidence of decorated trees associated with Christmas Day were those in Livonian guildhalls, where the tress were adorned with sweets for apprentices and local children. Legend has it that the first Christmas tree was brought to Tallinn, Estonia, in 1441 by the Brotherhood of the Blackheads, a Livonian merchants’ association. If this is true, that would make it the first Christmas tree placed in a town square in Europe.

Yule Log – To those of us who love Christmas delicacies, there’s nothing better than a Chocolate yule log or bûche de Noël. It originated in France and Belgium, where it’s known as Kerststronk in Flemish. Yule logs consist of a chocolate sponge roll layered with cream. The outside is covered with chocolate or chocolate icing and decorated to look like a bark-covered log. Some of them, like the one pictured here, can resemble log in the best trompe l’oeil (“fool the eye”) tradition. The best ones include extra decorations such as marzipan mushrooms. Here’s a recipe.

Long before it was chocolate cake, though, the Yule Log was a special log which, in Nordic tradition, was cut from fir or yew trees, into which was carved runes. It was then burned during the cold winter months to protect the household from evil spirits and misfortune. The custom of burning the Yule Log carried through into Medieval Europe. It was originally an entire tree, carefully chosen and brought into the house with much ceremony. The largest end of the log was placed into the fire hearth, lit from the remains of the previous year’s log which had been carefully stored away. The log was then slowly fed into the fire over the Twelve Days of Christmas. In its day, the custom of the Yule Log spread all over Europe and different kinds of wood are used in different countries.

It’s interesting that yew trees were used for burning, as they’re highly toxic. Yews are in the genus Taxus, Family Taxaceae, a group of coniferous trees that consists of around 5-7 genera and up to 30 species. They contain a number of toxic compounds, including taxine, a potent cardiotoxin. Being toxic is an important benefit for yew trees, as they can use this toxin not only to discourage browsing by herbivores, but can use it to poison the ground and out-compete other trees and shrubs that might overshadow their seedlings, in a process called allelopathy. Luckily for the Ancient Norse-people, burning yew wood itself is fine (according to Firewood-for-Life), as long as the bark and leaves are removed.

Mistletoe – Mistletoe is, of course, famous for promoting a kiss at Christmastime, when hung above a doorway. That was far more popular, and taken more seriously, in the 18th and 19th centuries, but even today, it’s firmly embedded in our culture. The tradition may have started among British servants who would steal kisses and pick berries as they did so. The kissing privilege would stop when the berries ran out. The Celtic Druids were among the first people known to ascribe a tradition to mistletoe, using it in ceremonies at least a few thousand years ago. They believed mistletoe, especially a species that grows on oaks, to have sacred and healing powers. As such, the Druids would collect it during the summer and winter solstices and may have been the first to use mistletoe to decorate houses in midwinter. It also featured in the Saturnalia of Ancient Rome.

European mistletoe Viscum album is a partial parasite, living on trees and drawing some nutrition from their hosts, adding to what they gain from photosynthesis. It’s an obligate parasite, meaning that it can’t complete its life cycle without living on its host. It’s a European plant, introduced into North America around 1900.

The plant is widely spread, parasitising over 200 plant species, with species ranging over much of the world. One of the reasons for mistletoe’s success is that they’re spread by birds that eat their fruit. From an evolutionary standpoint, it’s advantageous for birds that specialize in mistletoe to spread it as many places as possible. Mistletoe seeds are coated with a sticky substance that causes it to adhere to whatever it touches. This ‘glue’ soon hardens and attaches the seed firmly to its future host, where it germinates and then penetrates the bark. Some bird species have adaptations that make the process easier. Depending on the species of mistletoe and the species of bird, the seeds can be regurgitated from the crop and then excreted. Some birds pass the seeds through unusually shaped digestive tracts so fast that a pause for defecation of the seeds is part of feeding. In other species, the seed sticks to the beak, which the bird wipes onto a suitable branch. Some of these species even adopt a feeding behavior in which the bird grips the fruit in its bill and squeezes the sticky-coated seed out to the side. The seed sticks to the beak and the bird wipes it off onto the branch.

Holly (and Ivy) – As with the other plants that are green and fruiting in the winter, holly has bright red fruit to attract foragers that will disperse its seeds, and the fruit is a reward for services rendered.

The genus Ilex is distributed throughout the world’s climate zones. In Europe the genus is represented by a single species, the classically named holly I. aquifolium. And, although it’s often called English Holly, it’s native to western and southern Europe, northwest Africa, and southwest Asia. The flowers are attractive as nectar sources for bees, wasps, flies, and small butterflies and the berries are important food for birds and other animals. In the autumn and early winter the fruits are hard and seemingly unpalatable but, after being frozen , the fruits soften, and become milder in taste. During winter storms, birds often take refuge in hollies, which provide shelter and, because of their spiny leaves, protection from predators.

In pagan times, holly was thought to be a male plant and ivy Hedera helix a female plant. An old tradition from the Midlands of England says that whatever one was brought into the house first over winter, tells you whether the man or woman of the house would rule that year. The plants would be burnt together at the pagan festival of Beltane.

Poinsettia – Compared to the other plants, the poinsettia Euphorbia pulcherrima is a relatively recent addition to the Christmas botanical scene. A commercially important plant the species belongs to the diverse spurge family. Indigenous to Mexico and Central America, especially an area of southern Mexico known as ‘Taxco del Alarcon’ where they flower during the winter. Although the showy red bracts are actually modified leaves, rather than flower petals, they serve the same purpose as flowers – to attract potential pollinators. The ancient Aztecs called them ‘cuetlaxochitl’. The Aztecs had many uses for them including using the bracts to make a purple dye for clothes and cosmetics and the milky white latex was used as an antipyretic (reducing fever).

The poinsettia was described as a new species to science in 1834 and named after Joel Roberts Poinsett, the first Ambassador from the USA to Mexico in 1825, and notable detractor of slavery. Poinsett had some greenhouses on his plantations in South Carolina, and while visiting the Taco area in 1828, he became interested in the plants. He sent some of the plants back to South Carolina, where he began growing the plants and sending them to friends and botanical gardens. Surprisingly, despite being responsible for a US market of $149M annually, wild populations of poinsettias aren’t doing very well, mostly due to deforestation in their native dry tropics. Making matters worse is he potential for gene mixing with cultivars. Fortunately, the Mexican Government has protected the remaining populations, a first vital step in their long-term conservation.

A lot is made of bringing plants inside as a part of biophilic design, connecting to nature, purifying the air, and calming the senses. The concept of biophilia suggests that this innate desire to connect with other forms of life is innate. The depth of human history in which these traditions arise supports this idea and is testament to their importance. Interacting with these plants through our annual traditions causes us to appreciate even more the role of nature in our daily lives in ways we may not recognize consciously and makes a sound argument for its protection.

Best wishes for the festive season, however you celebrate it and a very happy new year.