Capsella bursa-pastoris（薺, ナズナ）

This plant makes the last weed pale in comparison, but only really in so far as weediness is concerned. This is, according to the Flora of China, the second most common weed on earth (I wonder what the first is; maybe the dandelion...). The same work also says that it's native to Europe and southwest Asia, but Ohwi's Flora of Japan makes no reference to it being introduced and he seems to disclude most non-native plants. I've personally seen it on 4 continents now: North America, South America, Europe & Asia, so the 2nd most common weed thing doesn't seem too far off. It grows virtually everywhere where there are people or open fields in the world's temperate zones. In Japan, Ohwi says it is "very common" on the 4 main islands in fields and streetsides in lowland areas.


The plant is called "shepherd's purse" in English because of its purse-like capsules (the capsules are called "silicles" in cabbage family-speak). In German, where I collected it for a class I was taking there, it's called "Hirtentasche", which means "heart purse", which I think is more obvious since I can't say I've ever seen a shepherd's purse. It has it's own kanji, 薺 (ナズナ), which is read as "nazuna". In simplified Chinese that character was reduced to 荠, which is "qi" in Mandarin, and it has the same meaning as the Japanese. In Traditional Chinese the character is the same as the Japanese one. However, the original meaning of the character was apparently "water chestnut", which in Japanese is クログワイ ("kuroguwai") and doesn't seem to be associated with a kanji. Meanwhile, the modern Chinese name for the water chestnut became 荸薺 (traditional) or 荸荠 (simplified). Notice that the second character in both compounds is the one used for shepherd's purse in modern Chinese. So my guess is that by the time the character was exported from China to Japan, shepherd's purse had been introduced to east Asia and the Chinese were denoting it using their old character for water chestnut unbeknown to the Japanese.

Anyways, I shouldn't waste too much time on this plant. It's really easy to identify because of its heart-shaped capsules. The leaves form a basal rosette that looks superficially similar to a dandelion rosette, but usually the plants occur en masse and are so sprawled out out dumping their seeds everywhere that you tend not to notice the leaves. The flowers are of the typical cabbage family (Brassicaceae) variety, which is to say they have 4 sepals, 4 clawed petals, 6 stamens and a bilocular ovary. The seeds are tiny and oblong.

Although Capsella bursa-pastoris (L.) Medik is superficially rather boring, it does have some interesting features. Coolest among them is that it has carnivorous seeds. The seeds secrete a mucilage when exposed to water, which gives off chemical signals that attract various small invertebrates. The inverts then become stuck to the seeds, which also secrete toxins to kill them and enzymes to digest them. What's the point of this? Fresh fertiliser for every seed! Another cool tidbit would be that all parts are edible and medicinal. The young leaves are apparently pretty good, but I haven't tried yet, while the older ones are said to be quite peppery. Medicinally, it's used by herbalists across the world for things such as eye diseases, dysentery and bloody noses.

Here are some links:
Flora of China treatment
Flora of Pakistan treatment
Flora of China illustration
MissouriPlants.com account
Barber (1978) "Capsella bursa-pastoris seeds: are they carnivorous?" (.pdf)