Shepherd’s Purse: The Protocarnivore On Your Doorstep

As I was walking home, a delicate plant growing en-masse around a tree pit caught my eye. With long stalks bearing tiny heart-shaped seed pods along its length ending in a cluster of small white flowers, it looked rather cute and innocuous. 

Cue my eccentric plant lady urge to crouch down and take some close up photos for your viewing pleasure:

What I’d found is Capsella bursa-pastoris, a plant commonly known as shepherd’s purse because the seed pods supposedly resemble the drawstring purses of old. It turns out the shepherd’s purse is a unique protocarnivorous plant, which means it is capable of trapping and killing insects much like the famous Venus Flytrap. However, unlike their carnivorous cousins, they lack the ability to directly digest nutrients from their prey.

For the shepherd’s purse, its prey of choice are nematodes. Seeds of the shepherd’s purse release a sticky mucilage during germination that attracts and ensnares nematodes, killing them and in so doing, enriching the soil. In a study published on Nature, researchers observed the killing spree in action and found that seedlings grown in soil containing nematodes thrived, growing much stronger and taller than their counterparts. Next time you see a particularly flourishing patch of shepherd’s purse, you’ll know that you’re probably seeing the results of a nematode massacre.  

Intriguingly, the same study mentions that shepherd’s purse along with some of its fellow Brassicaceae family members have demonstrated similarly deadly effects with mosquito larvae in previous studies. Upon exposure to dampened seeds, researchers observed impressive mortality rates in excess of 90%! Those charming seed pods aren’t so innocent after all . For unwitting invertebrates, they are heart-shaped parcels of doom.

For humans, shepherd’s purse isn’t lethal or toxic. In fact, it is by all accounts quite an appetising vegetable, with a peppery flavour profile. Unlike the US and Europe where it is widely perceived as a weed, it is cultivated throughout much of Asia. In China, it is known as jìcài (荠菜) and used for cooking in Shanghai and the surrounding area, featuring in soups, porridges and dumpling fillings. I found a great recipe for pork and jìcài dumplings (I haven’t tried it yet, but it looks and sounds delicious so I know exactly what I’ll make if I ever have some fresh shepherd’s purse to hand).






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