Following an extremely dry spring and summer further compounded by regular heatwaves, the autumn finally brought some good rain to the lower Hunter, and with the ongoing warm temperatures it was like having summer all over again, but without the heatwave.
While the crops were responding to the boost of rain, not to be forgotten are the weeds, just lying around dormant waiting for their moment. The most likely suspects, fireweed and capeweed (both daisies) however were usurped by a less likely but nonetheless quite common weed, known by many names including American wormseed and Mexican tea – the names giving some clue as to the origin.
This plant has a new botanical name since I last looked it up. Previously it was Chenopodium ambrosoides, sister to the common fat hen or lambs quarters, Chenopodium album and the popular health food quinoa (C. quinoa). However a quick check of the Plantnet site informs me it now has a new name, Dysphania ambrosoides, and that it is a cosmopolitan weed found throughout Eastern Australia and beyond.
While this plant isn’t particularly striking in appearance, it does have a quite distinctive smell, some may say stink! This is due to the volatile oil which is high in the monoterpene oxide ascaridole, a rare anthelmintic compound also found in the medicinal plant boldo (Peumus boldo). For over 100 years the essential oil (known then as Baltimore oil) was used as a household remedy in North America for treatment of intestinal parasites, however it became less popular due to its extreme toxicity. According to “Ëssential Oil Safety” a safe dose for children was 1 drop per year of age, but 2-3 times that dose could be fatal. In a study by Monzote et al. (2009), cytotoxicity via inhibition of mitochondrial respiration by three different components of the essential oil (ascaridole, carvacrol and caryophyllene oxide) was demonstrated.
So how does such a toxic substance become a food ingredient? Travel to Mexico and epozate as it is known is a much-loved culinary spice, added to beans and other dishes to assist digestion and add an aromatic flavour. The trick is to use the leaf only, not the seeds, and avoid the essential oil altogether. According to Mother Earth Living, you can add epazote to soups and stews, bean and squash dishes, corn, pork and fish, mushrooms with onions and to complement other popular spices like cilantro and chiles.
So there you have it – a weed, medicinal herb and essential oil, food and poison all in one. Do you have any weeds to match that in your garden?
Monzote, L., et al., (2009). Toxic effects of carvacrol, caryophyllene oxide, and ascaridole from essential oil of Chenopodium ambrosioides on mitochondria. Toxicol. Appl. Pharmaco. doi:10.1016/j.taap.2009.08.001
Tisserand & Balacs (1995). Essential Oil Safety. Churchill Livingstone.