There are those who say that they get messages from plants and that plants actually speak to them with a human voice, telling them the healing virtues of an herb. Others (like me) get pictures in their minds that seem to be another form of direct communication from the plant world. Over the millennia many other plant identification and communication systems that do not rely on the written word have been devised.
The Doctrine of Signatures
Centuries ago in Europe, in a time before most people could read, a system called the “doctrine of signatures” was developed to catalog the language of plants. With this plant classification system in their head, illiterate people with no access to a printed herbal could encounter a plant they had never seen before and divine its medicinal properties.
I have successfully used this system to understand the medicinal properties of a plant, and it is great fun to look the plant up later to see if others have determined the same thing. The first thing is to get used to using all of your senses: touch, sight, smell, and taste. Next, be aware that this system works only with wild plants growing in their natural habitat, or with “invasives” that have chosen, without human intervention, to incorporate a certain set of light and soil conditions. Nonnative species that have been planted by humans do not give accurate readings!
Here is an overview of some elements of the doctrine of signatures. Once you have these in your mind, it’s easy to ferret out the properties of an unfamiliar herb.
Where is the plant growing, in sunlight or in shade? Plants that crave a lot of sun will generally bring dryness and heat into the body; examples include Elecampane (Inula helenium), Sunflower (Helianthus annuus). Plants that thrive in the shade tend to be cooling; examples include Elderberry (Sambucus nigra, S. canadensis), and Peppermint (Mentha piperita, M. balsamea Willd.).
Is the plant growing in a wet place or a dry place? Plants that thrive in damp areas will help with conditions such as rheumatism, fevers, colds, and coughs; examples include Willow (Salix spp.), Mint (Mentha spp.), Vervain (Verbena hastata, V. officinalis), Sweet Flag (Acorus calamus), Elderberry (Sambucus nigra, S. canadensis), Boneset (Eupatorium perfoliatum), Jack-in-the-Pulpit (Arisaema triphyllum), Skunk Cabbage (Symplocarpus foetidus), and Sundew (Drosera rotundifolia, D. anglica, D. linearis).
Plants that are used to dry up mucky soil will help dry mucous secretions; examples include Sunflower (Helianthus annuus), and Eucalyptus (Eucalyptus globulus).
Plants that grow in or around clear ponds and fast-moving brooks tend to be diuretic and will help clear the urinary tract of waste; examples include Horsetail (Equisetum hyemale), Bedstraw or Cleavers (Galium aparine), Mint (Mentha spp.), and Alder (Alnus serrulata).
Plants that thrive in gravel and rock formations will help clear stone-forming and catarrhal accumulations from the bronchial and alimentary systems; examples include Bearberry (Arctostaphylos uva-ursi), Horsetail (Equisetum hyemale), Peppergrass (Lepidium virginicum), Parsley (Petroselinum crispum), Shepherd’s Purse (Capsella bursa-pastoris), Juniper (Juniperus communis), and Sassafras (Sassafras albidum, S. variifolium).
Does the plant grow in thin or disturbed soil? If thin soil, it is a plant that likes to struggle and will bring grit and strength to the body, such as Horsetail (Equisetum hyemale).
Alone or in a Group
Is the plant growing alone or in a group? Solitary plants are telling you they are powerful and need to be treated with cautious respect. For example, you will never see a field of Yarrow, but a field of Clover or Dandelion is often seen. Plants that grow in masses such as Red Clover (Trifolium pratense) are more gentle in action or esculent.
Does the plant grow near people or as far away as it can manage? Plants that grow on your doorstep, like Dandelion (Taraxacum officinale) and Plantain (Plantago major), can be used safely for a long time. Plants that grow in the deep woods, such as Goldenseal (Hydrastis canadensis) and Blue Cohosh (Caulophyllumthalictroides), have more specialized uses and should only be used for a short time period. Plants that grow in fields, the middle distance between house and forest, such as Yarrow (Achillea millefolium) and Saint-John’s-Wort (Hypericum perforatum), can be used for a while but only during special seasons or for a certain period of time.
The Signatures of Stems and Roots
Does the plant have hollow stems? If so, it will help clean tubes in the human body such as the bronchi and alimentary tract; examples include Comfrey (Symphytum officinale), Onion (Allium cepa), Garlic (Allium sativum, A. canadense), Thyme (Thymus serpyllum, T. vulgaris), Irish Moss (Chondrus crispus, Gigartina mamillosa).
Check out the roots. Are they deep or shallow? Thick or thin? Plants with very thin, threadlike stems and roots, which imply the sewing up of lesions, are often skin healers; examples include Bedstraw or Cleavers (Galium aparine), Tormentil or Septfoil (Potentilla tormentilla), Cinquefoil (Potentilla reptans), Gold Thread (Coptis greenlandica).
Very fine and meshed roots are a signature for healers of the nervous system; examples include Valerian (Valeriana officinalis), Lady’s Slipper (Cypripedium calceolus, C. pubescens).
Annuals have small thread-thin roots. These plants are mostly Fire and Air.* They do not live longer than one year and lack strong Earth energy; thus they are not grounding to the body and mind. However, they will help raise a person’s spirits, lighten that person’s outlook, and promote change. Their medicinal properties will be concentrated in the leaves and flowers.
*For an explanation of the four elements—Earth, Water, Fire, Air—see the section “Classification according to the Four Humors,” page 17).
Biennials are plants that grow over a two-year life cycle. They have large fleshy roots that store energy to get them through the dark, cold winter. In their first year they have no flowers or seeds and their healing virtue is concentrated in their roots. In their second year the energy moves to the flowers or berries and ultimately the seeds, which is where their medicinal properties will be found; examples include Carrots and Queen Anne’s Lace or Wild Carrot (Daucus carota), Beets (Beta vulgaris), Burdock (Arctium lappa), Parsnip (Pastinaca sativa), Salsify (Tragopogon spp.), Raspberry (Rubus idaeus). These plants tend to have sweet roots that are nutritive due to their high carbohydrate content.
Perennials are plants that come back every year. Some, such as deciduous trees, Reeds (Phragmites communis), and Comfrey (Symphytum officinale), may appear to die back in the winter. Conifers, of course, stay green all year. These plants have very large and deep roots and more even energy distribution. Even in winter their twigs and roots will provide medicinal aid.
Leaf Shapes and Texture
Understanding the structure of leaves can point to the uses of a plant. For example, Liverwort (Hepatica spp.), used to heal liver conditions, has a leaf that is three-lobed, like the liver. Comfrey (Symphytum officinale) leaves have “cells” and tiny hairs that look like human skin as seen under a magnifying glass. It is one of the greatest skin healers and a healer of areas of the human body that have small hairs, such as the nose, throat, and intestines.
Plants with very soft leaves will often ease pain in a diseased or injured area; examples include Mallow (Malva rotundifolia), Horehound (Marrubium vulgare), Hollyhock (Althaea rosea), and Mullein (Verbascum thapsus), whose leaves were once used as a wound dressing.
Spotted leaves point to tumorous growths and pus sacks on infected lungs; examples include Saint-John’s-Wort (Hypericum perforatum), Lungwort (Pulmonaria officinalis).
Overall Shape and Formations
Plants that help the eyes, such as Eyebright (Euphrasia officinalis), look like an eye, while the seeds of Skullcap (Scutellaria spp.) resemble a cap or helmet, pointing to its use to help sleeplessness, headaches, and nerve problems.
A skull-like shape reveals a brain healer, such as Walnut (Juglans spp.) and Skullcap (Scutellaria lateriflora).
Plants with a groin-like shape are used to overcome sterility and sexual lethargy; examples include Mandrake (Mandragora officinarum), Poke (Phytolacca americana), Ginseng (Panax quinquefolius), Bryony (Bryonia dioica).
Plants with long trailing root systems and vines that resemble veins and the nervous system of the body are often blood purifiers, nervines, and antispasmodics; examples include Sarsaparilla (Smilax spp.), Woodbine (Lonicera periclymenum), Licorice (Glycyrrhiza glabra), Bittersweet Nightshade (Solanum dulcamara), Grapes (Vitis vinifera), Hops (Humulus lupulus), Mints (Mentha spp.), Cinquefoil (Potentilla reptans), Dog Grass (Agropyron repens), Bearberry (Arctostaphylos uva-ursi).
Trees with bark that has openings and tears or “lenticels” are a signature for broken skin and thus skin healers; examples include Birch (Betula spp.), Elder (Sambucus spp.), Cherry (Prunus spp.), Sumac (Rhus typhina).
If a plant has thorns it is probably edible and evolved the thorns to protect itself; examples include Raspberry (Rubus idaeus), Blackberry (Rubus villosus), Rose (Rosa spp.). Thorns are also a signature for sharp pain. Thorny plants relieve pain, not by sedating it but by striking at the root cause of it. Hawthorn (Crataegus spp.), for example, is a tonic for angina and all manner of heart conditions. Other such plants are Prickly or Wild Lettuce (Lactuca virosa, L. serriola), Motherwort (Leonurus cardiaca), Blessed Thistle (Cnicus benedictus), and Raspberry (Rubus idaeus), which eases labor pains. Strawberry (Fragraria spp.) and Blackberry (Rubus villosus) contain malic and citric acids, which break up formations that lead to kidney and gall stones.
Hairy plants relieve “stitch in the side” types of pain; examples include Nettles (Urtica dioica), Sumac (Rhus typhina), Mullein (Verbascum thapsus), Currant (Ribes spp.), Hops (Humulus lupulus), Sundew (Drosera rotundifolia, D. anglica, D. linearis). Plants that sting stimulate internal circulation of fluids; examples include Ginger (Zingiber officinale), Nettles (Urtica dioica).
Plants with compact flower clusters can deal with an intense accumulation of pus in the throat and tonsils and are astringents for tonsillitis and sore throats; examples include Sumac (Rhus typhina), Self-heal (Prunella vulgaris), Hardhack (Spiraea tomentosa).
Wart-like growths and galls, such as growths on Sumac (Rhus typhina) and galls on Oak (Quercus spp.), contain tannins and gallic acid, which are astringent and pull together the edges of a wound.
Lichens and molds are useful for skin conditions such as psoriasis, which they resemble.
Moisture and Stickiness
Mucilaginous plants will soothe the throat; examples include Acacia (Acacia spp.), Tragacanth (Astragalus adscendens, A. gummifer, A. brachycalyx, A. tragacanthus), Irish Moss (Chondrus crispus), Hollyhock (Alcea spp.), Slippery Elm (Ulmus fulva), Mallow (Malva rotundifolia), Lungwort (Pulmonaria officinalis), Flaxseed (Linum usitatissimum).
Plants that contain a lot of resin are often healers of moist lesions, cuts, and ulcers; examples include Balsam of Peru or Tolu Balsam (Myroxylon balsamum pereirae), Benzoin (Styrax spp.), Mastic (Pistacia lentiscus), Pine (Pinus spp.), Myrrh (Commiphora myrrha), Turpentine (from Pinus spp.), Aloe (Aloe spp.). Plants with a sticky mucilaginous sap are also great itch healers; examples include Aloe (Aloe spp.), Pine (Pinus spp.), Comfrey (Symphytum officinale). If they are very juicy and wet (Aloe spp.), they will help swell excretions and benefit the colon.
If a plant is very dry and lacking in juice, such as Sage (Salvia officinalis), it will be good for drying up secretions such as catarrh and breast milk.
A plant that sticks to itself will cling to and remove hardened mucus; examples include Sage (Salvia officinalis), Coltsfoot (Tussilago farfara), Horehound (Marrubium vulgare), Life Everlasting (Gnaphalium obtusifolium, G. polycephalum), Mallow (Malva rotundifolia).
Plants that are highly aromatic are also disinfectant and deodorizing; examples include Thyme (Thymus serpyllum, T. vulgaris), Rosemary (Rosmarinus officinalis), Lemon (Citrus limon), Juniper (Juniperus spp.). For bad breath and body odor, examples include Marjoram (Origanum marjorana), Mint (Mentha spp.), Rosemary (Rosmarinus officinalis), Anise (Pimpinella anisum).
Other aromatics are antiseptic, germicidal, and antibiotic; examples include Tansy (Tanacetum vulgare), Pennyroyal (Mentha pulegium), Sage (Salvia officinalis), Savory (Satureja hortensis), Fennel (Foeniculum vulgare), Basil (Ocimum spp.).
Plants that stink are used for indolent, foul ulcers; examples include Stinking Arrach (Chenopodium olidum).
The color red points to the blood and the plant is likely a blood purifier or beneficial to the heart; examples include Red Clover (Trifolium pratense), Burdock (Arctium lappa), Rose (Rosa spp.), Raspberry (Rubus idaeus), Bee Balm (Monarda fistulosa, M. punctata, M. fistulosa var. menthifolia, M. didyma), Hawthorn (Crataegus spp.).
Yellow flowers are associated with the liver and gall, jaundice, and yellow bile; examples include Dandelion (Taraxacum officinale), Celandine (Chelidonium majus), Goldenseal (Hydrastis canadensis), Barberry (Berberis vulgaris), Lemon (Citrus limon).
White-blooming flowers point to bone healing; examples include Boneset (Eupatorium perfoliatum), Comfrey (Symphytum officinale).
Blue and purple flowers point to a plant that will improve the complexion and may also be a remedy for cyanosis (a blueness of the skin resulting from lack of oxygen in the blood and impaired arterial flow); examples include Joe Pye Weed (Eupatorium purpureum), Red Clover (Trifolium pratense), Vervain (Verbena hastata, V. officinalis), Burdock (Arctium lappa), Gentian (Gentiana lutea), Chicory (Chichorium intybus).
Nature in her kindness has given us a signature for poisonous herbs—the color maroon—which we can see, for example, in the berries and stems of Poke (Phytolacca americana), and the streaks of maroon found up and down the stems of Water Hemlock (Cicuta spp.), the herb that did in Socrates.
There is an old adage: “Bitter taste, sweet to the stomach, sweet taste, bitter to the stomach.” Plants that are yellow and bitter, such as Dandelion (Taraxacum officinale), benefit the liver, while plants that are yellow and sweet, such as Astragalus root (Astragalus membranaceus) and Elecampane (Inula helenium), are building to the stomach, spleen, and pancreas.
Plants that are sour and taste like lemons are telling you they have a lot of vitamin C. Plants that taste like carrots have a lot of carotene or vitamin A. Lichens will taste of the minerals in the rock they are growing on. Spinach, high in iron, actually tastes like iron ore. Plants that taste like garlic contain sulfur and can help clear heavy metals out of the body.
Pain-killing plants will deaden the lower lip when tasted.
The Signatures of Foods
Slice a carrot and you will find radiating spokes that look like the human eye. Carrots contain vitamin A, which is very beneficial to eye health. Onion cells under the microscope look like human cells. They help clear waste from cells and cause tears, which clean the epithelial layers of the eyes. Tomatoes are red and have four chambers, just like a human heart. They, like all red fruits and vegetables, benefit the heart, blood, and circulation. Grapes hang in heart-shaped clusters. Grapes are great blood and lymph cleansers and contain resveratrol, which helps the heart.
Walnuts look like little brains, with left and right hemispheres and wrinkles that resemble the neocortex. Walnuts are known to improve brain function. Kidney beans actually do benefit the kidneys. Sweet potatoes resemble the pancreas and can help balance blood sugar levels. In Chinese medicine orange foods are said to benefit the Earth element and the pancreas.
Avocados are shaped like the female womb, and it takes nine months to grow an avocado from seed to fruit. In turn, avocados balance hormones, help women shed pregnancy weight, and prevent cervical cancers. Olives help the ovaries, which they resemble in structure. Pomegranates, which are larger but also resemble the ovary filled with blood and eggs, are cleansing to the female reproductive tract. Citrus fruits, such as grapefruits, oranges, and others, resemble mammary glands. They help move lymph in and out of the breasts.
Figs hang in clusters of two and are filled with seeds. They increase the number and motility of sperm.
The Contribution of Intuition
Once you have the basics down you can let your intuition lead you further. For example, when I sat before a Cardinal Flower (Lobelia cardinalis), I thought immediately of a fire engine, of burning, redness, fever, and sparks before the eyes. That seemed way too obvious and I didn’t think it could be so easy. Then I went and looked it up in Clarke’s materia medica, and here was what I found:
There is a proving* of Lob. card. by S. D. R. Dubs, who took ten drops of the tincture in one dose. Dubs’ symptoms have been confirmed by a second proving by Kopp (H. W., xxxi. 26). The acrid properties of the plant were immediately felt by Dubs, in burning in mouth and throat, which lasted a long time. Sticking and pricking sensation in various parts, especially left chest and left hypochondrium. Oppression of breathing. Headache at base of occiput burning in tongue and fauces. Many symptoms occurred at 8 a.m. Sleepy but difficulty in sleeping. A lady to whom Cooper gave one dose of Lob. cd. had “flashes of light before eyes every day for a week.” It seems, he says, to have an action distinct from that of other Lobelias, since a dose of it brought back pains which had been relieved by Lob. dort.
*In homeopathy, a dilute amount of the herb, mineral, or other substance is taken until a “proving” or symptom picture results. The symptoms that appear in the provings are compared to those of a sick person; if properly matched, the person who takes the remedy will heal.
The Ancient Chinese System of Plant Classification
In addition to the system of classification by plant signatures, other systems also were used in ancient times. Thousands of years ago the Chinese developed a system of plant classification based on temperature, flavor, and direction. Armed with this knowledge, an herbalist could identify which plants were most useful for a particular illness.
The Four Natures or Temperatures
Chinese herbalism divides herbs into warm, hot, cool, and cold. A cooling or cold plant is suitable for a “yang” (congested, full, toxic) hot disease, and a hot or warm herb is given for a “yin” (dissipating energy, debilitated, chilly) cold disease. Some herbs are considered “neutral” and can be given for both cold and hot conditions.
The Five Flavors
Plants are also classified according to flavor: sour, bitter, sweet, spicy, and salty.
Sour-tasting herbs are known to stop secretions, contract tissue, and promote digestion and liver function. Examples are Lemon (Citrus limon), Rose hips (Rosa spp.), Hawthorn berries (Crataegus spp.), and Chinese Dogwood (Cornus officinalis).
Bitter-tasting herbs are cooling, anti-inflammatory, and antiviral, and they help clear parasites from the body. They improve stomach function, clean the blood via the liver, clear cholesterol from the venous system, and help the heart. Examples include Goldenseal (Hydrastis canadensis),* Gentian (Gentiana lutea), Centaury (Centaurium umbellatum, Erythraea centaurium), and Mugwort (Artemisia vulgaris).
*Goldenseal root is tonic to the system when taken as no more than one-tenth part of a formula. Taken alone, Goldenseal becomes an antibiotic and must be treated with caution, as with any antibiotic. After a course of Goldenseal, take plain yogurt, sauerkraut, miso soup, raw apple cider, or any probiotic supplement to restore intestinal flora.
Sweet-tasting herbs are building and nourishing. Foods and herbs that contain complex carbohydrates, proteins, and sugars are found to be nutritive and building to the body. Examples are Ginseng (Panax quinquefolius), Rehmannia root (Rehmannia glutinosa), Date (Phoenix dactylifera), and Barley malt (Hordeum vulgare L.).
Spicy herbs and foods are drying and warming to the body. They are useful for mucous congestion, arthritis, colds, flu, and menstrual cramps when taken internally; applied topically they relieve bruising and injuries. Examples are Red Pepper (Capsicum annuum), Cinnamon (Cinnamomum verum, C. cassia), Ginger (Zingiber officinale), and Prickly Ash (Zanthoxylum clava-herculis, Z. americanum).
Salty-tasting herbs are cooling and moistening to the body, because of the way they help the organs retain water. Seaweeds (marine algae) are a good example of this kind of plant.
Bland-tasting plants such as mushrooms are classified as mildly sweet and diuretic.
The Four Directions
In Chinese philosophy every substance in nature is understood to float, sink, rise, or descend, depending upon its inherent qualities. Seasons are also seen to have these characteristics: summer has floating energy, fall has descending energy, winter has sinking energy, and spring has ascending energy.
Leaves and flowers have ascending energy, making them useful for acute, surface-level diseases such as colds and flu. Barks, roots, seeds, and berries have sinking energy and thus move deeper into the system to aid chronic conditions.
What’s in a Name?
When you look at an herbal you will notice that a plant may have several common names. Pay attention to the folk names for herbs, because the old-timers named them that way for a reason.
Eyebright (Euphrasia officinalis) got its name because it helps the eyes. Liverwort (Anemone hepatica) is called that because it helps the liver (wort is an old word for “herb”).
Mouthroot or Gold Thread (Coptis greenlandica) is good for ulcers and mouth sores. Heartsease (Viola tricolor) leaves are a tonic for the heart. Kidneywort (Cotyledon umbilicus) helps with inflammation and kidney stones. Lungmoss (Lobaria pulmonaria) helps with pulmonary problems. Skullcap (Scutellaria lateriflora) is for headaches.
Other examples are Cough Herb (Tussilago farfara), Puke Weed/Asthma Weed/Indian Tobacco (Lobelia inflata), Heal-all (Collinsonia canadensis), Self-heal (Prunella vulgaris), Nosebleed (Achillea millefolium), Colic Root (Dioscorea villosa), Boneset (Eupatorium perfoliatum), Dysentery Bark (Simaruba amara), Feverwort (Erythraea centaurium), Pilewort (Ranunculus ficaria), Scabwort (Inula helenium</span