Herbs are about the only thing I can grow that aren’t eaten by birds, possums and skinks.

Except when the cats decide to self-bathe in the wonderful aroma of my herbs, when someone lets them out onto the piece of concrete substituting for a back yard.

Seven of the 12 dried oregano samples sampled by Choice Australia contained other ingredients, including olive and sumac leaves.

Last year a study reported that 25% of dried oregano samples in the UK were adulterated. Concerned that Australian consumers might be affected by the same issue, CHOICE decided to carry out a spot check on the authenticity of oregano being sold here. We bought a selection of dried oregano products from supermarkets, grocers and delis in Sydney, Melbourne and Perth – 12 different brands in total – and had a single sample of each product analysed.

Shockingly, the results of a unique screening test for oregano adulteration showed that of the 12 samples, only five were 100% oregano. The other seven – from brands Master of Spices, Hoyt’s, Stonemill (Aldi), Spice & Co, Menora, Spencers and G Fresh – contained ingredients other than oregano, including olive leaves (in all seven samples) and sumac leaves (in two samples). Ingredients other than oregano made up between 50% and 90% of the adulterated samples.

It’s important to note that we tested just one sample of a single batch from each brand, so the results aren’t necessarily representative of each of those individual brands and companies’ whole range of oregano products.