Which Lungwort? A Flowering Plant and a Lichen Share the Name

Most herb pages can open with the plant. This one cannot, because the word lungwort does not identify an organism. It identifies a resemblance. At least two completely unrelated living things have been called lungwort for the same reason — each was thought to look like a lung — and they are not related in the way that two mints or two mustards are related. One is a flowering plant. The other is a lichen, which is not a plant at all.

That is not a pedantic distinction and it is not botanical trivia. The two organisms share no compound classes, no safety profile, no habitat and no supply chain. Every study, every caution and every traditional claim on this site's lungwort pages has to be tagged with which organism it belongs to, or it becomes borrowed evidence of the most basic kind. And a reader who buys a bag of dried “lungwort” online may receive either one, because both are sold under that name today.

So this page does the identification work first. It describes both organisms, measures how far apart they actually are, tells you how to tell dried fragments of one from the other, states plainly which one the site's Lungwort page treats, and explains why the ambiguity is a safety problem in both directions rather than a curiosity.

Table of Contents

  1. Two Organisms, One Name
  2. Pulmonaria officinalis: The Spotted Woodland Herb
  3. Lobaria pulmonaria: Not a Plant at All
  4. How Far Apart They Really Are
  5. Two Chemistries That Do Not Overlap
  6. Which One Is in the Bag You Bought
  7. Other Organisms That Have Worn the Name
  8. Which One This Site Treats
  9. The Lichen Has a Conservation Problem the Plant Does Not
  10. Why the Ambiguity Is a Safety Problem
  11. Key Research Papers
  12. Connections

Two Organisms, One Name

Here are the two, stated as plainly as possible.

Pulmonaria officinalis is a small perennial flowering plant of European woodlands, in the borage family (Boraginaceae). Its dark green leaves are blotched with pale, milky spots, and to medieval European eyes that mottling looked like the surface of a diseased lung. The Latin genus name comes directly from pulmo, lung. In herbal texts the dried aerial parts appear as Pulmonariae herba.

Lobaria pulmonaria is a large foliose lichen that grows on the bark of old trees. A lichen is not a plant, not a moss and not a single organism: it is a stable partnership in which a fungus builds the visible body and houses photosynthetic partners inside it. Lobaria pulmonaria's upper surface is a network of raised ridges and sunken pits, and that pitted, chambered look was read as the inside of a lung. Older pharmacy called it Lichen pulmonarius, and its long-superseded botanical synonym Sticta pulmonacea still turns up in nineteenth-century herbals.

The two organisms have precisely one thing in common: a human being looked at each of them, thought of a lung, and named it accordingly. That is the whole of the relationship. There is no shared ancestry within any recognisable distance, no shared biochemistry, and no reason at all to expect that what is true of one is true of the other.

Pulmonaria officinalis: The Spotted Woodland Herb

Common lungwort is a low, clump-forming perennial of deciduous woodland, shady hedge banks and stream sides across much of Europe. It is one of the early spring flowerers, pushing up before the tree canopy closes, and it rarely exceeds about knee height even in flower. Three features make it recognisable:

The folk names are worth listing, because they show what people actually saw. Our Lady's milk drops and Mary's tears read the pale spots as milk spilled by the Virgin. Jerusalem cowslip, spotted dog and spotted comfrey are descriptive. Only lungwort itself is a claim, and the next page in this section is about how that claim was generated.

One point about the genus matters later. Pulmonaria contains something on the order of a dozen to twenty accepted species depending on the authority consulted — among them P. obscura, P. affinis, P. longifolia, P. mollis, P. angustifolia and P. saccharata. Several are close enough that P. obscura was long treated as a subspecies or variety of P. officinalis, and the two are separated in the field mainly by whether the leaves are spotted at all. Meanwhile, almost everything sold in garden centres as “lungwort” is a named cultivar or a garden hybrid rather than wild P. officinalis. Since the chemical work discussed on these pages was done on named species and not on cultivars, a garden plant is not automatically the plant in the papers. We flag that rather than paper over it.

Lobaria pulmonaria: Not a Plant at All

Tree lungwort is one of the largest and most conspicuous leafy lichens of northern temperate forests, forming lobes that can reach the span of a hand or larger on the trunks and mossy limbs of old broadleaf trees. Wet, it is a soft bright green; dry, it turns dull brown or grey-green and becomes brittle. The upper surface is unmistakable: a raised network of ridges enclosing shallow depressions, with pale powdery patches along the ridge tops from which it reproduces vegetatively. The underside is paler and downy, with bare patches.

What it is made of is the interesting part. The visible body is built by a fungus — a member of the Ascomycota, in the family Lobariaceae, now often placed within a broadened Peltigeraceae. Under current fungal naming conventions, the binomial Lobaria pulmonaria formally names that fungus. Inside the fungal tissue live photosynthetic partners, and in this species there are two kinds:

A lichen with both a green algal and a cyanobacterial partner is called tripartite, and tree lungwort is one of the textbook examples. So the thing a herb supplier dries and chops is a consortium of at least three organisms from three different branches of life, functioning as one body.

Two consequences follow that matter for anyone thinking of drinking it. First, a lichen has no roots, no vascular tissue and no waxy cuticle. It takes up water — and everything dissolved or suspended in that water — directly across its whole surface from rain, mist and dust. That is why lichens are used as air-quality monitors, and it is also why a wild-harvested lichen carries whatever the local air has been depositing. Second, tree lungwort is a slow-growing organism of continuous old forest that disperses poorly, which is the root of the conservation problem discussed below.

How Far Apart They Really Are

It is tempting to file this under “two different plants with the same common name,” the way plantain the herb and plantain the banana get confused. That comparison badly understates the distance here. Plantain the herb and plantain the banana are at least both flowering plants.

Here is the honest framing. Fungi and animals sit together in one great branch of the eukaryotes; plants and green algae sit in another. Put bluntly: the fungus in tree lungwort is more closely related to you than it is to the borage-family plant it shares a name with. The green alga tucked inside the lichen is, if anything, the nearest thing in the partnership to Pulmonaria, and it is still separated from it by the entire evolution of land plants.

This is why the phrase “lungwort has been shown to…” is unusable without a Latin name. Two herbs in the same genus can differ enough in chemistry that a result from one does not transfer to the other — that caution appears throughout this site, and it applies within Pulmonaria itself. Between a flowering plant and a lichen there is nothing to transfer at all.

Two Chemistries That Do Not Overlap

The clearest way to see the gap is to lay the reported constituents side by side. Neither list is exhaustive, and both are summarised in more detail on the respiratory-use page and the safety page.

Pulmonaria officinalis leaf has been characterised reasonably well by modern analytical chemistry. Reported constituents include mucilage and other polysaccharides; a large fraction of caffeic-acid derivatives dominated by rosmarinic acid, together with related oligomers such as lithospermic, salvianolic and yunnaneic acids; flavonoid glycosides; tannins; soluble silicic acid; allantoin; vitamin C; and trace pyrrolizidine alkaloids of the kind found across the borage family. The detailed profiling work by Krzyżanowska-Kowalczyk and colleagues in Molecules (2018) is the single most useful reference here, and it establishes that the phenolic acids make up the great bulk of the plant's measurable antioxidant chemistry.

Lobaria pulmonaria makes compound classes that flowering plants essentially never make. Lichens are chemically distinctive: their characteristic secondary metabolites are depsides, depsidones and dibenzofurans, built by the fungal partner and often deposited as crystals on the surface of the hyphae. In tree lungwort the reported metabolites centre on the stictic-acid group of depsidones — stictic, constictic and norstictic acids and relatives — along with depside-type compounds such as tenuiorin and methyl orsellinate, and the structural β-glucans of the fungal cell wall.

Read those two paragraphs again and note that not one compound class appears on both lists. No mucilage claim, no rosmarinic-acid finding and no pyrrolizidine-alkaloid caution belongs to the lichen. No depsidone chemistry belongs to the plant. This is the whole reason these pages label the organism at every citation rather than once in a preamble.

Which One Is in the Bag You Bought

Both are on sale as “lungwort” right now, and the pattern is roughly geographic rather than absolute. European herbal suppliers and the older pharmacopoeial tradition generally mean Pulmonaria officinalis when they write lungwort. A number of North American bulk-herb suppliers list “Lungwort” as Lobaria pulmonaria, sometimes with the clarifying names tree lungwort, lung lichen or lungmoss. We are not going to put a percentage on that split, because we have not surveyed the market systematically and a made-up figure would be worse than none.

What we can give you is a way to tell them apart, because the two look nothing alike once you know what to look for. Dried and chopped, the tells are:

  1. Venation. A leaf fragment of Pulmonaria has a midrib and a branching network of veins. A lichen fragment has none, because it has no vascular tissue at all. This single check settles most cases.
  2. Texture when wetted. Drop a fragment into water. Lichen thallus swells within a minute or two into something soft, rubbery and translucent green. Dried leaf goes limp and stays papery.
  3. Surface pattern. The lichen's raised ridge-and-pit network survives drying and is visible on any fragment larger than a fingernail. Pulmonaria fragments are flat, bristly, and may carry the pale spots.
  4. Associated parts. Cut-and-sifted Pulmonaria usually includes bits of hairy stem, and sometimes dried flower or calyx. A lichen has no stems, no flowers and no seeds — if you find any, you are not holding a lichen.
  5. Colour. Dried Pulmonaria is a dull green to grey-green leaf colour. Dried tree lungwort is characteristically brownish or ashy grey-green and leathery.

The practical rule follows from all of this: buy nothing labelled only “lungwort.” Require the binomial on the label, and if the seller cannot supply one, treat the product as unidentified material. The site's coltsfoot regulation page makes a closely related argument at length: when you cannot establish what is in the bag, the hazard is worse than the labelled species' hazard, not better, because you have lost the ability to apply any safety profile at all.

Other Organisms That Have Worn the Name

Two is the minimum, not the total. A handful of other organisms have carried “lungwort” or been folded into its reputation:

There is a historical wrinkle worth flagging. In parts of the older materia medica the lichen was the more prominent of the two, listed as Lichen pulmonarius or under the synonym Sticta pulmonacea, and there are nineteenth-century sources in which “lungwort” unqualified means the lichen. So it is not safe to assume that an antique text saying lungwort means the flowering plant; the identification has to be read out of the description, not the name.

Which One This Site Treats

Stated once, plainly, so nothing downstream is ambiguous: this site's main Lungwort page treats Pulmonaria officinalis, the spotted borage-family woodland herb. Its safety section, its chemistry section and its traditional-use section are all about that plant.

These Benefits pages follow the same convention. Where the lichen is discussed — and it is discussed, because a reader may well have bought it — it is named Lobaria pulmonaria or “tree lungwort” every single time, never just “lungwort.” Any sentence on these pages that says only “lungwort” means the plant.

The Lichen Has a Conservation Problem the Plant Does Not

This is the one place where the two organisms differ in a way that has nothing to do with pharmacology and everything to do with whether it is reasonable to harvest them.

Pulmonaria officinalis is common across much of its European range, thoroughly domesticated, sold in every garden centre, and in places naturalised outside its native range as a garden escape. Picking it, growing it or buying it raises no conservation question worth writing down.

Lobaria pulmonaria is the opposite case. It is a slow-growing epiphyte that depends on old, continuously wooded habitat, disperses inefficiently, and is strikingly sensitive to air pollution — sulfur dioxide in particular. It disappeared from large tracts of industrial and post-industrial Europe during the twentieth century and has recolonised only patchily where air quality improved, because recolonisation requires both clean air and old trees to arrive on. It appears on numerous national and regional red lists across Europe as threatened, endangered, vulnerable or near-threatened depending on the country, and it is one of the standard indicator species used to identify forests of high conservation value. It is also a well-studied model organism in lichen population genetics precisely because its dispersal is so limited.

We are deliberately not attaching a growth-rate figure to this species. Large foliose lichens are generally described as growing on the order of millimetres per year, which makes a hand-sized thallus the product of many years and a mature population the product of decades of undisturbed forest, but a confident number for L. pulmonaria specifically would be a guess and we are not going to make one.

The conclusion does not need a number. Wild-harvesting a slow-growing, red-listed, old-growth-dependent lichen to make a tea for which there is no clinical evidence is a poor trade, and it is a completely different act from picking a woodland herb that self-seeds into gardens. If you want the traditional respiratory experience, mullein, marshmallow root, thyme and ribwort plantain are abundant, cultivated, better studied and cost a threatened organism nothing.

Why the Ambiguity Is a Safety Problem

It would be easy to treat all of this as taxonomy for its own sake. It is not, for four concrete reasons.

  1. The two hazard profiles are unrelated. The plant's principal open safety question is a family-level one: Boraginaceae members contain pyrrolizidine alkaloids, some of which are hepatotoxic. The lichen's questions are entirely different — lichen secondary metabolites, contact sensitisation, and accumulation of airborne contaminants. Apply the wrong profile and you get both errors at once: worrying about a hazard that is not present, and missing one that is.
  2. Every citation has to be labelled. A paper on Pulmonaria antioxidant activity says nothing whatever about tree lungwort, and vice versa. This is the crudest possible form of borrowed evidence, and it is easy to commit by accident when the common name is shared.
  3. Unidentified material cannot be assessed at all. As the coltsfoot pages argue, the standard reassurance “the harm was really from a substituted species” clears the named plant and simultaneously indicts the supply chain. If you cannot tell whether your bag is a flowering plant or a lichen, no safety section on this site applies to it.
  4. The conservation cost is real for one and zero for the other. A purchasing decision made in ignorance of which organism is involved cannot take that into account.

One last observation, which is really the subject of the next page. The reason two organisms this unrelated ended up sharing a name is that neither was named for what it does. Both were named for what they look like, by people applying the same theory of resemblance. Once you see that, the shared name stops being a coincidence and becomes evidence about the method — a method that assigned a fungus-alga partnership and a borage relative to the same organ, on sight, and was satisfied.

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Key Research Papers

Every entry below is labelled with the organism actually studied. Links are PubMed topic and title searches rather than fixed record numbers, so they stay valid as the index grows.

  1. [Pulmonaria officinalis] Krzyżanowska-Kowalczyk and colleagues, “Novel Phenolic Constituents of Pulmonaria officinalis L. LC-MS/MS Comparison of Spring and Autumn Metabolite Profiles,” Molecules, 2018 — PubMed. The most detailed chemical map of the leaf, and the source for rosmarinic acid and related caffeic-acid oligomers dominating the phenolic fraction.
  2. [Pulmonaria officinalis and P. obscura] Krzyżanowska-Kowalczyk and colleagues, “Pulmonaria obscura and Pulmonaria officinalis Extracts as Mitigators of Peroxynitrite-Induced Oxidative Stress and Cyclooxygenase-2 Inhibitors,” Molecules, 2021 — PubMed. Notable here because it studies two lungwort species side by side, which is exactly the comparison most sources skip.
  3. [Pulmonaria officinalis] Neagu and colleagues, “Antioxidant activity, acetylcholinesterase and tyrosinase inhibitory potential of Pulmonaria officinalis and Centarium umbellatum extracts,” Saudi Journal of Biological Sciences, 2018 — PubMed. In-vitro enzyme assays; see the respiratory page for why the tyrosinase result does not mean what marketing copy sometimes implies.
  4. [Pulmonaria obscura — note the species] Haberer and colleagues, “Pyrrolizidine alkaloids in Pulmonaria obscura,” Planta Medica, 2002 — PubMed. Reports lycopsamine-type alkaloids concentrated in roots and rhizomes with only traces in leaves. Widely quoted as if it were about P. officinalis; it is not.
  5. [Pulmonaria officinalis and Borago officinalis] Lüthy and colleagues, “Pyrrolizidine alkaloids in medicinal plants of Boraginaceae: Borago officinalis and Pulmonaria officinalis,” Pharmaceutica Acta Helvetiae, 1984 — PubMed. One of the few measurements made on the species actually sold in Europe. It is four decades old and in German.
  6. [Boraginaceae, family level] Reviews of pyrrolizidine-alkaloid distribution across the borage family, including El-Shazly and Wink's survey of structures, distribution and biological properties, map which genera carry which alkaloid types — PubMed topic search. Note that some of this literature appears in journals with patchy PubMed coverage, so a title search may return nothing even where the paper exists.
  7. [Lobaria pulmonaria] Chemistry of the lichen — stictic-acid-group depsidones and related depsides — PubMed topic search. Compare the yield of this search with the Pulmonaria searches above: the two organisms have separate and non-overlapping literatures, which is the point of this page.
  8. [Lobaria pulmonaria] Population biology, dispersal limitation and conservation status of tree lungwort — PubMed topic search. The species is a standard model for lichen population genetics because it disperses so poorly, which is also why it does not come back quickly after logging.
  9. [Lichens, general] Lichen photobiont identity, including the reassignment of the Dictyochloropsis group to Symbiochloris — PubMed topic search. Relevant because it establishes that the green partner in tree lungwort is a specific identified alga, not a generic one.
  10. [Lichens, general] Lichens as biomonitors of airborne metals and radionuclides — PubMed topic search. This body of work is the reason a wild-harvested lichen is an uncontrolled exposure as well as an uncontrolled dose; it is discussed on the safety page.
  11. [Neither organism] A search for controlled human trials of either lungwort in respiratory illness — PubMed topic search — returns nothing usable. That empty result is a finding, and the respiratory page treats it as one.

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Connections

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