Capsella bursa-pastoris Seeds | Shepherd’s Purse
LATIN NAME: Capsella bursa-pastoris
COMMON NAME: Shepherd’s Purse
Plant Profile
Kneel beside almost any path in lowland Europe in late spring and you meet a plant that has solved seed dispersal with a piece of flattened leather. The fruit of shepherd’s purse is an obcordate silicle, a two-valved capsule split by a papery septum and notched at the tip, so it reads as a purse with two clasps. Its flattened orientation turns the valves into a spring that tosses seed onto compacted ground.
Field pennycress carries a round, disc-like silicle with a broad wing, and Arabidopsis thaliana a long slender cylinder; shepherd’s purse alone has the triangular, heart-notched fruit. The rosette is equally telling, with deeply lobed leaves over a deep taproot. The genus holds three familiar species: the tetraploid shepherd’s purse, the selfing Capsella rubella and the outcrossing Capsella grandiflora.
Shepherd’s purse is an allotetraploid with thirty-two chromosomes, assembled from two diploid lineages resembling modern Capsella grandiflora and Capsella rubella. A mixed mating system compounds the effect: small cleistogamous flowers set seed low on the stem while showier cross-pollinated flowers open above. Pressed specimens vary so much that the species has collected dozens of minor names.
Archaeobotanists lift its seed out of waterlogged prehistoric and medieval deposits across Europe, because the netted coat survives burial and the plant grows so willingly around settlement. The coat is myxospermous: on wetting, outer epidermal cells release a mucilage envelope that glues the seed to soil and lets it pass through a bird or a grazing animal.
Plant biologists watch mating-system change here because Capsella rubella is a recent self-fertilising offshoot of the outcrossing Capsella grandiflora. Comparative genomics examines how floral size, pollen output and the self-incompatibility locus are lost or retained, with the tetraploid standing alongside as counterpoint.
Science & Biotechnology
The chemistry is that of a working mustard: flavonoid glycosides of kaempferol, quercetin and luteolin, the amines choline and acetylcholine, tyramine, and the choline ester sinapine. Glucosinolates give the crushed leaf its bite, and vitamin K is present at levels that make the plant more than a casual salad ingredient.
The envelope is a pure polysaccharide gel, so the seed coat has become a laboratory subject in its own right, studied for how it holds water against a drying surface and how it might carry a treatment onto a seed. In the field the same gel explains why the plant colonises mud so quickly.
Uses & Benefits
John Gerard’s Herbal of 1597 lists shepherd’s purse among the wound herbs, a reputation it carried into the nineteenth century in poultices and infusions. Its culinary life is quieter but older: the young rosette, gathered before the stems rise, is mild and faintly mustardy.
Take the whole rosette while the leaves lie flat and the central bud is tight, then wash it through two changes of cold water to lift grit out of the lobed bases. It goes raw into spring salads or wilts in a covered pan with a little fat. Once the stems elongate the leaf turns fibrous.
Because it establishes in cool weather, shepherd’s purse works as a quick field-edge cover and as poultry forage, and hens strip the seed from standing stems. It also feeds small bees and hoverflies early, when few other flowers are open on the headland.
Growing from Seed
Sow onto a fine, firm surface, because the seed is small and light-dependent. Use two parts sieved loam, one part coarse sand and one part leaf mould, firm it, and broadcast thinly. Press the seed in with a board and dust over no more than two millimetres of compost, then mist and hold the surface damp under glass. In open ground, mark rows about thirty centimetres apart.
Thin the plants to roughly ten centimetres, the width of a spread hand, once they carry three or four true leaves, and water afterwards to settle the roots. Keep the bed clear of larger competition, because the plant is a coloniser of open ground and stalls under a dense canopy.
Sow thinly and keep air moving. Aphids cluster in the growing tip, flea beetles riddle the young leaves with shot holes, and downy mildew of the crucifers stains crowded seedlings. Pull the thinnings and move the crop to a fresh patch each season.
Our Take
If you grow shepherd’s purse at all, grow it for the early rosette and let a few plants run to the purse stage so that you can study the fruit at close range. Anyone wanting a dependable cool-season supply of the family should look at arugula and brown mustard, or at maca if the interest is an Andean root rather than a lowland leaf.
Related Reading
Gardeners who grow Shepherd’s Purse often pair it with these related subjects: