Once thought lost, a specimen of Aconitum lamarckii (Ranunculaceae), the yellow monkshood has now re-established itself in our front garden, not far from where it was originally planted. Leaning out from under the more substantial Persicaria polymorpha (white fleeceflower), I first noticed the blooms about a week ago. Most people are familiar with the blue forms of monkshood, the bi-colored Aconitum x cammarum being most popular, followed by the blue, purple or white forms of Aconitum napellus. The yellow monkshood is a looser, less upstanding citizen of the garden and many will want to stake it or cage it, but in a naturalistic garden, surrounded by other plants, its sagging ways will not be so irritating. Like all in the Aconitum genus, they share the common name Wolfsbane, which indicates their toxicity. All parts of the plant contain the alkaloid aconitine which is a highly poisonous alkaloid , a neurotoxin:
“It is quickly absorbed via mucous membranes, but also via skin. Respiratory paralysis, in very high doses also cardiac arrest, leads to death. A few minutes after ingestion paresthesia starts, which includes tingling in the oral region. This extends to the whole body, starting from the extremities. Anesthesia, sweating and cooling of the body, nausea and vomiting and other similar symptoms follow. Sometimes there is strong pain, accompanied by cramps, or diarrhea. There is no antidote, so only the symptoms can be treated, traditionally with compounds such as atropine, strychnine or barakol, although it is unclear whether any of these are effective. Some other toxins such as tetrodotoxin which bind to the same target site but have opposite effects, can reduce the effects of aconitine, but are so toxic themselves that death may result regardless.”
Suddenly, gardening is not such an innocent pastime!
While the poison is most concentrated in the roots, all parts of the plant are toxic. I don’t wish to overstate the danger, but a bit of common sense when handling the plant is advisable, especially for those with heart conditions, sensitive skin or open wounds on the hands. Work with gloves when working on the plant, especially when dividing the roots, and be sure to wash your hands afterwards. A summary of a paper on Aconite poisoning by Thomas Y.K. Chan (Clinical Toxicology, April 2009, Vol. 47, No. 4, Pages 279-285) can be found here. One benefit of the toxins is that Wolfs-banes are considered resistant to deer or rabbit browsing, which can be an important feature for some gardeners.
Other species that are hardy in zone 3b are A. carmichaelii, which can be such a late bloomer that it will be cut-off by the first frost; A. henryii, commonly sold as “Spark’s Variety”, also a late bloomer and the many varieties of the previously mentioned A. x cammarum and A. napellus.
Culturally they all favor similar conditions, that is dappled sun to part-shade and moist feet. They can be placed in full sun but be sure they have good moisture. In good conditions they can grow to a height of 1.2m (48″) and have a spread of about 75 cm (30″). They can be prone to powdery mildew if they do not have enough water. They are also subject to the pest moth Delphinium leaf-tier, Polychrysia esmeralda. Leaf-tier is best dealt with by pinching off the gathered leaves as soon as they are noticed, usually in late May.
While the garden varieties of Monkshood are Eurasian in origin, there is a species native in Alberta, Aconitum delphinifolium. The Alberta Native Plant Council has a list of suppliers which may possibly have seeds of this plant.