Spurge laurel

The most definitive thing to be said about spurge laurel is that it isn’t.

It isn’t spurge, it isn’t laurel, and although it’s noxious and unpleasant and toxic, it isn’t definitively useful to the individual thinking about bumping off their mother-in-law or their boss or their ex, or any number of other potential subjects, unless the subject is a very small child.

(Aside #1: As previously noted in The Backyard Poisoner, it’s remarkably easy to bump off a small child with plants from the backyard—either accidentally or on purpose—so much so, in fact, that at a recent family dinner, during which I invited my eight-year-old nephew to help himself to blueberries from the garden, my sister gave me a pointed look and I had to reassure her that there was absolutely nothing poisonous in the garden that he could possibly mistake for a blueberry. At least, nothing currently ripe. I said this last bit under my breath, of course, but I can assure readers that my nephew lived long enough after eating the blueberries to ingest three large hamburgers, four large pieces of corn and an extraordinarily generous slice of blackberry pie with ice cream. I’m almost certain that the stomach-ache he experienced later that evening was due to factors other than the handful of berries before dinner.)  

What it also isn’t: spurge laurel isn’t officially classified as a noxious weed under British Columbia’s Weed Control Act, which means the ambitious gardener can cultivate multiple specimens without raising the hackles of government regulators. Whether it’s worth the gardener’s time to do so is less certain.

For the serious backyard poisoner, the real human harms of spurge laurel (Daphne laureola) remain elusive. Various informational materials are available online and in regional collections—ranging from mostly useless to somewhat informative to downright sensational—but most of them reference each other in a maddeningly circular way.

For example, many refer to a child in Nova Scotia who died after ingesting spurge laurel berries, but I have yet to independently verify this macabre event. Most texts refer to Worksafe BC materials for this information—and, indeed, Worksafe BC does have a one-page “fact sheet” that states “a child died in Nova Scotia after eating the berries”,[1] but it provides no primary source reference for the story. After many hours of research, I have begun to wonder if the story is more legend than fact—though I would welcome from readers any indications otherwise.

The Nova Scotia case reminds me of the hapless Vancouver Island–based gardener who took all reasonable precautions to root out spurge laurel from a client’s garden—gloves, mask, long canvas pants—and then made the mistake of transporting the cuttings in an enclosed vehicle. She inhaled the fumes of the plant and went into a coma, from which she [died/never recovered/recovered only after many days/suffered lasting mental effects].[2]

(Aside #2: I was told this tale by a fellow gardener more than a decade ago and have heard several versions repeated to me since, with the phrases in square brackets representative of the story’s various endings. I have yet to find this event in a news article, a coroner’s report, or a medical journal, though I remain hopeful.)

The most sensational descriptions are generated by local gardeners with a significant web presence—and who refer ominously to the poor Nova Scotia child while promising a specialized and expert (read: expensive?) “comprehensive approach” to the eradication of a dangerous killer lurking in your garden, masquerading as a rhododendron, poisoning your pets and your children.[3] No doubt these are the same sorts of militant gardeners who neutralize death cap mushroom threats and put down uprisings of water hemlock.

(Aside #3: Rhododendrons are also toxic, but we don’t go around eradicating them; we just tell our kids not to eat them. This is a good reminder that the line between plants that are food and plants that aren’t is much the same as the line between plants that aren’t poisonous and plants that are. Over a long history of trial and error, humans have learned what plants can be eaten without ill effect. “Food” is just “things that have nutritional value and don’t typically kill you”.)

The most believable assessment of spurge laurel’s toxicity is from a comprehensive reference on our more undesirable flora, The Biology of Canadian Weeds, which reports that three berries of the spurge laurel have killed a pig and two or three berries contain enough toxin to “fatally poison” a child.[4] But a close study of this reference and a brief detour through the archives of the Invasive Species Council of BC reveal that spurge laurel is a far more predictable killer of environmental habitats than of humans.

Native to southern Europe and northern Africa, spurge laurel was first identified in British Columbia in Victoria at Government House, where a specimen was collected in 1958.[5] Since then, the plant has become naturalized throughout southwestern British Columbia but is especially prolific on Vancouver Island, where it wreaks havoc on natural ecosystems, including sensitive Garry oak forests and Douglas-fir habitats. The perennial evergreen shrub loves shady woodlands and spreads easily, its broad, glossy leaves (which double in size between April and June) forming a dense layer of foliage that blocks any sunlight from reaching the forest floor. If you walk through an area where spurge laurel has become habituated, you’ll see that the ground beneath the plants is bare. The natural regenerative capabilities of native species are greatly reduced wherever spurge laurel has proliferated. Within a few years, the soil chemistry is altered, which further inhibits the ecosystem’s capacity to regenerate.[6] Thus, spurge laurel really is a sure and merciless killer, slowly strangling its victims over time.

Spurge laurel (Daphne laureola)

For humans and other animals, however, results are variable. All parts of the plant contain poisonous compounds (daphnetoxin, mezerein, and dihydroxycoumarin). These compounds can be fatal if ingested in large enough amounts, but the leaves of spurge laurel have also been used medically to create a strong purgative. The berries of the plant are poisonous to most mammals but have also become an important food source for mice and some birds. The coumarin glycosides in the bark are toxic to humans and most other mammals.[7]

The sap of the plant is corrosive—good for inducing skin irritation in an intended victim but potentially dangerous to the backyard poisoner who likes to garden in the nude. Contact with the sap can cause skin rashes, nausea, and swelling of the tongue—although not, apparently, in all cases; some people are more sensitive than others. In cases of extensive prolonged contact, some sources indicate coma is a possibility—perhaps following the respiration of toxic chemicals when the plants are removed with mechanical tools or when cuttings are transported in an enclosed space.[8]

Perhaps the tale of the unfortunate Vancouver Island gardener isn’t a myth after all.

Gardener’s notes:

Evergreen shrub similar in appearance to a medium-sized rhododendron, growing up to 1.5 metres in height and circumference. Leaves are broad and glossy green and grow larger in spring. Flowers are small and yellowish-green, slightly fragrant but otherwise unappealing. Berries are black and ripen in dense clusters in June (a single plant can produce as many as 600 berries in a season, so unless you want 600 spurge laurel plants by next season, harvest with a firm hand). Spurge laurel prefers shade or dappled shade but will tolerate sun and spreads aggressively, pushing out other species and, over time, negatively impacting soil composition.

The savvy gardener is much better off with a rhododendron.

First responder’s notes:

If spurge laurel poisoning is suspected, an immediate trip to the nearest hospital is recommended. Ascertaining whether the toxin was ingested or inhaled will be helpful for the attending medical practitioner. Transporting the plant specimen in your enclosed medical vehicle will not be helpful for anyone.

Writer’s notes:

Not worth the writer’s time.

Pro:

Almost no pros. Definitely a killer, but not predictably a human killer. Incorporating spurge laurel into the manuscript might provide a reasonable red herring—but so would many other more interesting garden specimens. 

Contra:

So many. Too many to number.

Pathologist’s notes:

A determination of daphnetoxin poisoning (daphnetoxin being one of the most potent toxic compounds in Daphne laureola) could be made based on a victim history and a post-mortem examination that points to respiratory inflammation and organ damage, but the toxin itself breaks down quickly in the body and may not be detectable.

Murderer’s best-case scenario:

Kill the victim in some other way and stash the body under the dense foliage of spurge laurel in the back garden of any number of misguided property owners who think spurge laurel is an attractive woodland planting. For best results, kill and stash between the months of April and June, when the plant’s foliage becomes even more dense and growth is most aggressive.

Final score (taking into account toxicity, certainty, detectability, and ease of use, including preparation and clean-up): 2/10

 
Footnotes:

[1] WorkSafe BC, “Toxic Plant Warning: Severe skin irritation from Spurge Laurel (Daphne laureola)”, n.d.

[2] Like WorkSafe BC, I have provided no source reference at all for this story.

[3] I absolutely have a source reference for this, but because I would be outing a local business, I have decided not to provide it.

[4] M. Strelau et al., “The Biology of Canadian Weeds: 156. Daphne laureola L.” The Canadian Journal of Science, March 28, 2018.

[5] Government House is the official residence of the royal family in British Columbia. The house is set within expansive gardens generally open to the public from dawn until dusk. Eager amateur gardeners can help tend the property under the guidance of professionals, thus gaining valuable insight into both toxic and non-toxic specimens. In 2016, my children and I watched Prince William and Princess Catherine (then Duke and Duchess of Cambridge) and their two children, Prince George and Princess Charlotte (Prince Louis was still an abstract concept), drive through the wrought iron gates at the beginning of the royal tour. I did briefly consider the illustrious history of spurge laurel in that moment, but there is no documented evidence that any members of the royal family have ever been harmed by plants growing in the royal gardens.

[6] M. Strelau et al.

[7] M. Strelau et al.

[8] M. Strelau et al.