
In early December, when winter has almost arrived in the Northern Hemisphere, most trees are pretty drab. The exceptions to this are evergreens, which remain green and leafy throughout the year. But even among evergreens, few are as colorful as holly (Ilex spp.).
Apart from being associated with Christmas, holly has other distinguishing characteristics. First among these are its leaves, which are tipped with thorns and range in size from almost nonexistent to downright gargantuan. Also notable are its berries, which are usually red — though other colors can be found — and provide the most striking visual cue to the identity of holly, allowing it to stand out vividly in a world of gray skies and white snow.
And though there hasn’t yet been snow in central North Carolina where I live, the holly in my front yard — a Chinese holly (Ilex cornuta) that I’ve pruned to the size of a bush — is most certainly producing those red berries, begging for some kind of recognition.
Folklore
Since many people are first acquainted with the holly tree through the song The Holly and the Ivy, it only makes sense to start with the folklore surrounding it.
Most prominent in that folklore is the holly’s association with Jesus, either at his birth or on the cross. In The Holly and the Ivy, for instance, the white flowers and red berries are said to symbolize Jesus at his birth, bringing light and color into a world of death and decay. Similarly, other interpretations have compared holly leaves to the crown of thorns worn by Jesus on the cross, the white flowers to his purity, and the red berries to his blood.
But there are older associations as well. For their part, the Druids of Britain and Ireland considered the holly tree sacred because it was able to withstand the cold of winter and produce fruit even in the greatest hardship. The Romans similarly regarded it as a symbol of steadfastness and sent it, along with a token of goodwill, to friends around the time of the Saturnalia — the date of which later became Christmas. And even some Native American tribes considered holly sufficiently sacred to put it around their dwellings to ward off evil spirits.

Living in a modern culture of concrete and plastic, most people would consider these associations somewhat far-fetched. But holly has other associations which are not so far-fetched. These come from Western herbalism and Traditional Chinese Medicine (TCM), and a few of them have even been confirmed by science.
Medicinal Uses
[Before harvesting or consuming wild plants, make sure you have the permission of the landowner and an understanding of considerations for use.]
Although holly isn’t quite as powerful as ginger, garlic, echinacea, or even dandelion, it nonetheless has some noteworthy medicinal uses. In TCM, Chinese holly (Ilex cornuta) is used to alleviate a number of health issues, including headache, toothache, rheumatism, and conjunctivitis. It’s also considered to be especially effective in the treatment of tuberculosis, in part due to a perceived ability to reduce “wind-damp.” (Wind is frequently cited as a cause of disease in TCM.)
In Western herbalism, there’s been an emphasis on holly’s calming and soothing properties. These include the ability to reduce fever, swelling, and arthritis throughout the body. In a similar vein, the bark of English holly (Ilex acquifolium) is occasionally recommended as a sedative, though I haven’t found this use cited as frequently as the others.
As with any medicinal plant, there are of course warnings that should be heeded. Foremost among them is to avoid the berries of all Ilex species. They are poisonous to humans and frequently cause vomiting or diarrhea, though they are rarely fatal.
Despite that caveat, even modern science has confirmed the anti-inflammatory properties of Chinese holly (I. cornuta) in particular. In the linked study, use of holly leaf extract resulted in reduced levels of biomarkers for inflammation, such as nitric oxide, prostaglandin, and interleukin. This would indicate that the use of holly leaf extract as a potential remedy for hypertension, rheumatism, and pain is in fact justified.

So, while we may never be able to say definitively that holly wards off evil spirits and embodies the purity of new life in the depth of winter, we can certainly say that holly possesses real medicinal properties, which were recognized by ancient peoples and which are relevant even in our modern culture of concrete and plastic.
And that’s as good a reason as any to hang some holly at your door.