The Secret Language of Plants

If you've ever seen a passionflower, you’ll notice the delicate tendrils spiralling outward from its centre, resembling the intricate branching of the nervous system.

According to the Doctrine of Signatures – an ancient belief that a plant’s physical appearance reflects its healing properties – this similarity is no coincidence. Passionflower is used by herbalists as a nervine: a remedy that soothes the nervous system, eases anxiety, and promotes deep, restful sleep.

The Doctrine of Signatures gained popularity in Medieval England during the 15th century, when it was believed that God had placed signs in nature to reveal each plant’s medicinal purpose. Naturally, this idea became controversial – especially among scientists and physicians who were moving toward evidence-based medicine and dismissed the doctrine as superstition.

Personally, I love this concept. It sparked my curiosity, and as a health advocate and food lover, I began exploring it further – especially the idea that foods resembling certain body parts might benefit them.

Walnut

Arguably the most iconic example, the humble walnut isn’t the easiest nut to crack - but once you do, its resemblance to the human brain is striking - and it’s not just coincidence. The brain thrives on healthy fats, particularly omega-3 fatty acids, which are known to reduce inflammation and support cognitive health. Walnuts are rich in omega-3s. A 2014 review concluded that including walnuts in your diet may help

prevent cognitive decline and dementia.

Beetroot

I’ve been a fan of beetroot since childhood – I love its earthy taste and deep red colour. But does it benefit the blood? As it turns out, yes. One of beetroot’s most notable benefits is heart health. It's a natural source of nitrates, which convert to nitric oxide in the body. This helps dilate blood vessels to lower blood pressure and heart rate.

Kidney Bean

Will the kidney bean hold up under the Doctrine of Signatures? While all beans offer protein, carbs, and essential minerals – and are generally beneficial for overall health, including kidney function – I didn’t find strong evidence linking kidney beans directly to improved kidney health. In fact, they contain oxalates, which can contribute to kidney stone formation in some individuals. For those prone to kidney stones, a low-oxalate diet is often recommended.

Mushroom

Next, the mushroom, which when sliced lengthways resembles the shape of the human ear. In Medieval times, mushrooms were thought to cure earaches, earning them a spot in the Doctrine of Signatures. Does this theory stand up today? Mushrooms are a natural source of vitamin D, which has been linked to cochlear health through its role in calcium metabolism. A 2013 study concluded that a vitamin D deficiency was associated with higher rates of ear infections in children.

Pomegranate

This one’s my favourite. The pomegranate – any guesses what it was believed to heal? Toothache. Modern science backs this up to an extent. Pomegranates have antibacterial properties that may help prevent plaque build-up, reducing the risk of gum disease and tooth decay. A 2024 review even found that pomegranate extract, when combined with fluoride, acts as an anti-demineralising agent, offering added protection for teeth.

Avocado

Creamy and nutrient-dense, the avocado bears a strong resemblance to the uterus. Coincidence? Perhaps not. A 2016 review  described avocados as a unique, nutrient-rich plant food that provides many of the critical nutrients needed for foetal development and maternal health. They’re a recommended part of prenatal nutrition for a reason.

Grapefruit

And finally – the grapefruit. With its bittersweet taste and breast-like appearance, some believed it could benefit breast health. Curious, I dug into the research… and this one fell flat. In fact, some studies have suggested grapefruit may increase the risk of breast cancer, particularly in postmenopausal women, due to its effect on oestrogen metabolism. Sadly, this signature failed miserably.

Out of the seven foods I explored, five waved the signature flag high. The Doctrine of Signatures is by no means an exact science and in some cases, it led to dangerous assumptions in Medieval times. But back then, most people didn’t have access to medicine, so the idea that healing could be found in the shape and colour of herbs or foods brought both comfort and hope.

Cath is co-founder of Dream Awake with her sister Fin Walker. They run workshops guiding individuals on a journey to reconnect with their true essence and remember who they are. Through this work, they help others dream their world into being. For a list of upcoming workshops, visit www.dreamawake.love/workshops.