Someone has called them an oddity of Nature, someone else a gift: they are the galls, or cecidia, swelling growths that characterize some trees, particularly oaks. They are very common in the plant kingdom and very rich in tannins.
They generally have an irregular round shape, which often leads to confusing them with fruits, and can vary in consistency: some are softer, others have either a cottony or a woody appearance and some others have spikes, like rose thorns. All these abnormal outgrowths of plant tissues have a common origin: they are a reaction of the tree to an external attack, generally carried out by bacteria, fungi or insects. In fact, they are made up of a mass of vegetable cells through which the plant “isolates” the infected part, so that the damage does not spread. A sort of arboreal “scar”.
A form of defense that the plant puts in place to protect itself from the substances secreted by insects, especially Hymenoptera (ants, bees and small wasps) and Diptera (flies and mosquitoes), but also mites and bacteria present on the plant, and which could damage it. It is therefore not surprising that they have a high concentration of tannin, a substance that exerts a remarkable antibacterial power on the injured part.
In the course of evolution, plants have developed tannins precisely to protect themselves from external attacks. An indispensable survival strategy, since the plant is not able to move and react in case of danger. Any part of the plant can develop galls, which, depending on the insect or the bacterium causing its formation, will have different shape, color and size. There is even a branch of biology dedicated to galls production in plants that is called cecidiology.
The most famous among galls, as already mentioned, are the oak ones (Quercus infectoria), available in two variants: Chinese galls and Turkish galls, widely used for large-scale tannin extraction. Once extracted, the gallo tannin appears curiously like a white powder, with different shades. It has a pungent and intense scent and is impalpable to touch.
In traditional medicine, galls are used for their astringent (anti-diarrheal), disinfectant and anti-inflammatory properties. They can be used as an infusion ingredient for gargles and rinses to treat hemorrhoids, fissures, canes and fistulas. If used in maceration with extra virgin olive oil they are a useful remedy in case of contusions and hematomas.
Gallo tannins have been known since ancient times: Greeks and Egyptians already used it to dye fabrics and to make ink for writing. However, their main application was and still is vegetable tanning of leather. Gallo tannins are in fact extremely effective tanning agents. Very versatile, they are also used in enology to stabilize the color in red wines and to improve the structure and prevent oxidation in white wines.
Last but not least, if you are a fan of DIY jewelry, on Etsy you can buy sets that include different kind of galls for handmade jewelry and even beautiful necklaces, earrings and pendants made with galls by skilled designers!