PLANT OF THE DAY brings you easy to digest information on science backed plants for health and medicine. Written by scientists, the aim is to help increase understanding of how effective plant medicine is. Plant of the day promotes the scientific research on select plant medicines and thereby helps bridge the gap between the worlds of plant medicine and general medicine.

DID YOU KNOW? While you can take a cup of chamomile tea to aid relaxation and sleep anytime, we always recommend that to treat a condition you consult a NIMH medical herbalist to ensure you take the right plant medicine for your individual needs and at the right dose. Always consult a NIMH medical herbalist and inform your healthcare provider if you are pregnant, have any medical condition or are taking any medication.

How do we know that a plant medicine works? The story so far

  • History

    Throughout history people have used the plants around them to help maintain health as preventative medicine and to effectively treat many common ailments such as skin and gut conditions, colds and flu and insomnia and anxiety. More recently, plants used as medicines historically to treat inflammation, pain and heart conditions, have key medical drugs derived from them, like aspirin from white willow bark, morphine from the opium poppy seed head and digoxin from foxglove flower and leaf.

  • Laboratory Studies

    Scientific research carried out across the globe since the 1980’s has given us laboratory studies, by the hundreds of thousands, that are helping to show exactly how each plant, and their chemical ingredients, produce an effect on the body and brain.

  • Clinical Trials

    But the gold standard in research is controlled clinical trials (human studies). There need to be many more, but for a number of plants there are now clinical trials that verify the plant’s safe medicinal use. In some cases, when tested, the plant medicine has been shown as effective as single drug medicine, with fewer side effects such as addiction. And with Public Health England reporting last year that up to a ¼ of all adults in the UK are prescribed drugs that could be addictive, to treat depression, insomnia, anxiety and pain, plant medicine may be essential as an effective alternative.
  • Meta-analysis

    Even better than a single clinical trial are reviews (meta-analysis) of all trials carried out for any one plant medicine. These reviews provide the best scientific evidence to verify the traditional use of a plant medicine (or drug) today – and for plant medicine there are too few of these also. Saint John’s wort (pictured) is one plant medicine, prescribed by GP’s in parts of Europe to treat mild to moderate depression, that has a meta-analysis showing its efficacy for treating mild to moderate depression (though it is not to be taken with a number of medications).

  • The Clinical Trial Method

    The clinical trial method, where the same treatment (or placebo) is given to a group of individuals to treat one condition, does not quite represent the practice of plant medicine. Medical herbalist’s most often prescribe a combination of plant medicines that are tailored to the exact needs of an individual and the combination reassessed at regular intervals. So one size does not fit all in plant medicine. Nonetheless, verifying the efficacy of a plant medicine by the clinical trial method is helping go some way to reinstate knowledge of plant medicine into medical curriculum and may eventually help place NIMH registered medical herbalists as treatment referrals in general practice.


Here we take a quick look at plant medicines used to aid immunity, treat respiratory infection or be antiviral. A number of plant medicines are often used to boost immunity and to protect against or treat infection during the winter months.

Plants like echinacea, rosehip, garlic, elderberry and thyme have laboratory research to show how they work to boost immunity, for example by increasing immune cell production and antibody response or by being antiviral against different virus types.

For some of these plants, like echinacea root, astragalus root, ginger root, liquorice root and elder berry, there have also been a limited number of controlled clinical trials in humans. These clinical trials indicate that in group comparisons of placebo and test plant, the plants, when taken at a particular dose, are effective as immunostimulants. NOTE: Echinacea and astragalus are contraindicated in some immune conditions.

Over the next few weeks we will look at 12 plants with controlled trial evidence (human studies) or bioactivity potentially relevant to protection against or treatment of viral infections (such as covid 19) with key activities including anti-viral, immunostimulant, respiratory health (coughs, colds, flu, pneumonia) as well as antiseptic skin protection.

This list excludes many more plants that have positive results from lab studies and are yet to be tested in controlled clinical trials.

Some of the plants we will look at are below (* indicates particular relevance) and we will also include plants that help boost mood, relieve stress and treat anxiety and insomnia.

*Astragalus root – immunostimulant, treats common colds and prevents respiratory infections

*Echinacea root: reduces respiratory infections, anti-viral and immune-boosting

Elder berry – reduces symptoms and duration of upper respiratory infections

Elecampane (pictured) root – immunostimulant (inulin)

Garlic bulb and wild garlic (ransoms) leaf – immunostimulant and antiseptic

Ginger root – immunostimulant and anti-viral

Ivy leaf – treats respiratory diseases

Liquorice root – immunostimulant

Rose berry (wild/ dog rose) – treats colds, immunostimulant ( vitamin C )

Sage leaf (Salvia officinalis) – antibiotic (eg. throat infections)

Tea tree essential oil – antibiotic

Thyme leaf – for coughs, respiratory infections as well as anti- viral