Field Guide
Like its ubiquitous Christmas cousin, this shrub offers a splash of colour to the winter gloom (but without the nasty sharps)
Like its ubiquitous Christmas cousin, Canadian Holly offers a splash of colour to the winter gloom (without the nasty sharps)
Known to many as Canadian (or Canada) holly, this attractive shrub has quite a few alternative names by which you may know it, depending on where you live: black alder winterberry, deciduous holly, inkberry, swamp holly and fever bush. There is no better name though, no more Canadian name, I think, than “winterberry.” It is the fruit of the most Canadian season. The way these bright red berries on denuded branches stand out against a snowy backdrop is a welcome splash of bright colour amid the drab hivernal palette.
Although its leaves don’t have the deep indentations associated with other species of holly, its binomial name, Ilex verticillata, comes from the Latin names for oak (ilex), which the foliage of other hollies resembles, and for whorled (verticillata), referring to the berries’ position around the stem. Growing to one to five metres tall — which is tall indeed—it can also form a dense thicket where conditions are wet. Like some but not all of its ilex cousins, it is dioecious (from the Greek meaning “two households”): there are separate male and female plants, with at least one male plant needed to pollenate the females. The plant produces globular red berries, about seven millimetres across, and small blossoms with five or more white petals. Its serrated, pointy foliage is dark
green with a high gloss. It is one of the subset of deciduous hollies: it loses its leaves each autumn. In doing so it becomes a distinctive and decorative addition to your somnolent garden. Cut and dried it is often used indoors as well.
As attractive as it is, Ilex verticillata is also poisonous, containing a toxin called theobromine, which is an alkaloid similar to the caffeine you get in cocoa or a cup of joe. Alkaloids are nitrogen-infused alkaline chemicals originating in plants: they are derived from amino acids, the essential foundations of proteins, which especially affect the nervous system. Theobromine and caffeine are similar in that they are related alkaloids, though theobromine is weaker in terms of its impact on the human nervous system and stronger in stimulating the heart: it raises your heart rate while opening up blood vessels. While the disruptive chemicals occur at their highest in the berries, the bark and leaves are also toxic. Copious quantities of these berries can result in dizziness, stomach pain, nausea, diarrhea, elevated pulse rate and low blood pressure, as well as drowsiness, particularly in children and small livestock. One can assume this is why it has traditionally been called fever bush.
Perhaps surprisingly, for something this disruptive to the system, winterberry plants historically have had numerous medicinal applications. There was a time when holly leaves and the bark were brewed tea to create a tonic, as well as a treatment for fevers. The bark was also made into a skin poultice to ease rashes and eruptions. And the berries were taken as a purgative intended to expel intestinal maladies and intruders. There is no scientific evidence to suggest that such remedies work at all, while there’s considerable proof they can be harmful. Do not use them this way. These folk applications have all been dismissed and supplanted by safe and effective medicines.
Still, winterberry has its uses. As a decorative addition to your winter garden, the plant’s vivid berries offer a splash of colour at a dreary time. And indoors, over the holiday season they provide a refreshing and Canadian alternative to the traditional common European holly.