by Piter Kehoma Boll
Blue is a relatively rare color in nature, but in some places it appears much more than in others. Flowers of plants in the family Boraginaceae are often blue. The forget-me-not is possibly the most popular example, but not the only one. Today our fellow is another blue flowered species that is also popular, not so much for its flowers though, but for its lung-like leaves, the common lungwort Pulmonaria officinalis.
Whenever you find a plant whose name refers to a body part, it most likely has to do with the ancient doctrine of signatures, the idea that a plant that resembles a human organ can be used to treat diseases on that organ. This is the case with the common lungwort and the common liverwort, which was presented here some time ago. The oval and kind of heart-shaped leaves of the common lungwort are slightly hairy on the upper side and marked by several white or pale spots. They were thought to represent an ulcerated lung and, therefore, used to treat diseases of the lungs. Although some studies revealed that lungwort extracts can present biological properties such as antioxidant, anti-inflammatory and wound healing activities, nothing has been found that is directly related to the lungs.
Found across most of continental Europe, the common lungwort is a small plant formed by a creeping rhizome from which the leaves sprout in the form of rosettes. It likes to grow on the forest floor, below the tree canopy, but dislikes places with too much shade. As a European species, it is very tolerant to cold, supporting temperatures as low as -29 °C.
In spring, between March and May, the flowers appear in inflorescences on elongated stems that grow from the leaf rosettes. They grow during a period in which the trees are only starting to produce new leaves so the flowers are fully exposed to the sun. Each inflorescence has 5 to 15 hermaphrodite flowers with five petals. The flowers start red and, as they age, they change color to purple and finally blue. This change in color occurs because the pigments are anthocyanins that are affected by pH, being red in acidic environments and blue in alkaline ones. The main pollinators of the common lungwort are bees and the plant only wants them to visit young, red flowers. As a result, the change in color helps direct the pollinators to the right flowers by signalling that the blue ones are uninteresting (and they, in fact, have no nectar anymore). But why does the plant keep flowers for longer periods instead of shedding the petals and producing fruits at once? Well, because the more flowers you have, the more pollinators you can attract from the distance. A large number of flowers makes you visible from far away but, as the pollinators come closer, the different colors guide them to the right spot.
The fruit of the common lungwort is a schizocarp, i.e., a small and dry fruit that splits into smaller portions, each containing a seed. In the case of the common lungwort, each fruit contains four seeds, and their main dispersers are ants. The ants collect the fruits, carry them to their colonies and feed the larvae with the fleshy portion, discarding the seed afterward.
The common lungwort is a popular plant because of its color-changing flowers and its resistance to cold, but, as we can see, this beauty hides an even deeper beauty caused by its interaction with the small creatures that share the same space with it.
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Chauhan, S., Jaiswal, V., Cho, Y. I., & Lee, H. J. (2022). Biological Activities and Phytochemicals of Lungworts (Genus Pulmonaria) Focusing on Pulmonaria officinalis. Applied Sciences, 12(13), 6678. https://doi.org/10.3390/app12136678
Meeus, S., Brys, R., Honnay, O., & Jacquemyn, H. (2013). Biological flora of the British Isles: Pulmonaria officinalis. Journal of Ecology, 101(5), 1353-1368. https://doi.org/10.1111/1365-2745.12150
Wikipedia. Pulmonaria officinalis. Available at < https://en.wikipedia.org/wiki/Pulmonaria_officinalis >. Access on 22 September 2022.
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* This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.