PLANT OF THE DAY brings you easy to digest information exploring science backed plants for health and medicine. Written by scientists, it aims to increase understanding of how effective plant medicine is as well as encourage simple dietary interventions to increase health and prevent disease. 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, for example, a cup of chamomile tea to aid relaxation and sleep anytime, to treat a condition with a plant medicine it is important to take the correct dose and prescription for your individual needs – and in that case always first consult a NIMH medical herbalist and inform your healthcare provider before giving to a child, 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 maintain health as preventative medicine and to treat many common health issues. Less than 200 years ago, plants were the only medicines. The chemical revolution meant that plant medicines used to treat inflammation, pain and heart conditions, became the source of medical drugs – respectively, aspirin derived from salicin in white willow bark, morphine from the opium poppy seed head and digoxin from the foxglove flower and leaf – all drugs on the WHO list of essential medicine.

    Today plant medicine is used across the globe to effectively treat issues such as skin and gut conditions, colds and flu and insomnia and anxiety. It is only now that science is catching up with just how effective plant medicine is. The UK is lagging behind other countries in making use of plant medicine in general medicine.

  • Laboratory Studies

    Though we may more recently have forgotten that plants are key as medicines, 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.

    Time of leaf harvest, climate, vegetative development stage, and extraction method can all vary the chemical nature of the extracted leaf – this is why it is important to ensure plant material is harvested at the correct time and that products are purchased from an established reputable standardised source or from your local NIMH registered medical herbalist.

  • Clinical Trials

    Lab studies show how a plant works, 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 placebo controlled 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 an essential addition to single drug medicine.
  • Meta-analysis

    Even better than single controlled clinical trials are reviews or meta-analysis of all trials carried out for any one plant medicine or drug. These reviews provide the best scientific evidence (and meta-analysis confirms this with statistics) to verify the traditional use of a plant medicine (or drug) today. For plant medicine there are currently very few of these. 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 to treat mild to moderate depression. It has also been shown to be as effective as drugs (SSRIs & TCAs) and with fewer side effects (though it must not be taken with certain medication).

  • 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 herbalists aim to treat the underlying cause of a health issue with plant medicine, as well as nutritional and lifestyle changes. Most often prescriptions are a combination of medicinal plants that are tailored to the exact needs of an individual. This combination is then reassessed at regular intervals according to the individual’s response to the medicine. So one size does not fit all in plant medicine.

    You can add to this complexity the fact that trials often lack a specification of the plant material tested. Active chemical ingredients in any one plant can change with the location and climate the plant is grown in, time of harvest, part of the plant used and method used to extract the compounds. All clinical trials on plant medicine need to specify the chemical profile of the plant material tested. That way real comparisons can be made between trials.

    Nonetheless, verifying how effective a plant medicine is by the clinical trial method is helping go some way to reinstate our knowledge of plant medicine into the medical curriculum and eventually help place NIMH registered medical herbalists as treatment referrals in general medical practice.

  • Find out more

    Consult a National Institute Medical Herbalist medical herbalist While you can take, for example, a cup of chamomile tea to aid relaxation and sleep anytime, to treat a condition with a plant medicine it is very important to take the correct dose and plants medicine/s for your individual needs – and in that case always first consult a NIMH medical herbalist and inform your healthcare provider before giving to a child, if you are pregnant, have any medical condition or are taking any medication.

    Always buy plant medicine from an established reputable source. We recommend first consulting a NIMH medical herbalist who can then prescribe the correct plant medicine for your individual needs and/or recommend a reputable source. Once you have your prescription you could even try growing your own – during the second world drug shortage meant that people were encouraged to grow the plant medicines for collective harvest for use by doctors. These plants included valerian the clinically backed plant medicine which is calming and sedative. Other plants also grown on the home front included (but do NOT grow these for use at home!) toxic ones like belladonna for atropine (speeds up heart rate), henbane and datura for hyoscyamine (for IBS/spasms), foxglove for digitoxin (increases heart force of contraction) and autumn crocus for colchicine (anti-nflammatory for gout).

    Find more safe plant medicines that science is verifying effective in two books written by Dilston Physic Garden’s neuroscientist and pharmacognosist – Grow You Own Physic Garden and Botanical Brain Balms.


Here we take a quick look at plant medicines to used support immunity, be antiviral or treat respiratory infection. A number of plant medicines are often used to aid 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 support immunity, for example by increasing immune cell production and antibody response or by being antibacterial and antiviral against different virus types and some also work to control inflammation and oxidation.

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 months we will look at plants with controlled trial evidence (human studies) and bioactivity potentially relevant to protection against or treatment of viral infections (such as covid 19) with key activities including anti-viral, immuno-stimulant, for respiratory health (including coughs, colds, flu, pneumonia) as well as antiseptic skin protection.

This list excludes many more plants that have positive results from lab studies – such as being anti-viral, anti-inflammatory, expectorant and decongestant – 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 infection

*Echinacea root: reduces respiratory infection, antiviral and immune-boosting

Elder berry – reduces symptoms and duration of upper respiratory infection

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 disease

Liquorice root – immunostimulant

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

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

Tea tree and other essential oils – antibiotic, antiviral, antifungal

Thyme leaf – for coughs, respiratory infections as well as antibacterial and antiviral