- Type
- Leafy Greens
- Difficulty
- Easy
- Season
- Spring
- Sowing
- From seed
Field pennycress
Thlaspi arvense
Glucosinolates · an early spring green picked from field margins
Field pennycress sits flat as a rosette along field and paddy margins in early spring. Its leaves are larger and thicker than shepherd's purse, which is why it was known as the coarse shepherd's purse, and the Herb section of the Donguibogam enters its seed as 菥蓂子 under an old Korean name meaning the seed of the coarse shepherd's purse. The nature is set down as slightly warm, the taste as pungent, with no toxicity, and the text notes that it grows everywhere and that the fruit is gathered in the fourth and fifth lunar months and dried in the sun. Shepherd's purse hangs triangular pods; pennycress hangs round, flat ones like coins, so the fruit alone settles which is which. What gets eaten is the young rosette before the flower stalk rises, blanched, rinsed cold and dressed. It carries the pungency typical of the cabbage family, which blanching softens, and it takes well to doenjang and perilla oil. When picking along a field margin, stay clear of sprayed ground and roadsides, and check every plant for greater celandine, which bleeds a deep yellow sap at the cut.
Year-Round Calendar
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Where It Grows
- Wild population Common nationwide on field margins, rice-paddy banks and roadsides, and conspicuous as a rosette in early spring.
- Wild population Grows widely from the northeast through North and Central China, where the seed is gathered as seongmyeongja (the medicinal seed).
- Wild population Grows in fields and along roadsides throughout the country.
A wild plant native to Eurasia, it has now naturalised across the temperate world, including North and South America and Oceania. Because its native range is continental in scale, no place-of-origin row has been created; and because it is not a cultivated crop, there are no production statistics either, so only the three East Asian countries where it is actually gathered and used are listed. It has recently been trialled in the American Midwest as a winter ground-covering catch crop and as an oil feedstock, but this is not yet at commercial scale and so has not been included.
- Optimum
- 10~20℃
- Range
- 2~28℃
- Hardiness
- Hardy
- Day length
- Long-day
Field pennycress is a winter annual: it germinates in autumn and passes the winter as a rosette, its leaves pressed flat against the ground. It is hardy enough to survive under snow, and once it has been through the winter cold, the flowering stalk rises as the days lengthen in spring. The cool season is its growing season, so it sets seed and dies back before the summer heat arrives.
In Korea Nationwide
It germinates in September or October, overwinters (passes the winter in the field) as a rosette, and is harvested the following year in March or April, before the flowering stalk rises. The month of sowing and the month of harvest do not fall in the same year. Since it comes up of its own accord on field margins and paddy banks, gathering it from the wild is the more common practice.
How to grow
- Light
- It comes up on its own along sunny field margins, paddy banks and verges. Sown deliberately, it wants half a day of sun or more
- Soil and depth
- Not fussy about soil. It takes especially well to bare ground, such as the edge of a freshly turned bed
- Spacing
- Where it comes up on its own, pick rather than thin. Sown deliberately, 10cm between plants is enough
- Watering
- No watering. It overwinters as a rosette and grows on spring rain
- Feeding
- No feeding needed. Rich ground draws the leaves up soft and thins the flavour
- Harvest
- March and April. Cut just above the root while the plant is still a rosette. Once the flower stalk rises the leaves toughen and it is no longer used as a green
What makes the difference. Leave a few plants where you picked to flower and drop seed, and the same ground carries them again the next year
Why this one is harder. It drops a great deal of seed and is treated as a weed in cultivated ground. To keep it in a corner of the plot, cut most of the plants before the pods ripen and leave only a few
Common problems
- Cabbage white caterpillars You will see Holes through the leaves, sometimes down to the veins What to do Being a brassica, it draws the same pests as cabbage. As the spring sun strengthens, check the leaf undersides and pick them off
- Aphids You will see Colonies at the stem tips around the time the flower stalk rises What to do On plants you intend to eat, wash them off with water rather than spraying. Plants that have already bolted are not used as a green
This page describes how a crop is grown and used. It does not claim health effects for any food, nor is it intended to prevent or treat disease. Component and study notes are references only and do not mean the same result occurs in people. Consult a medical professional about health concerns.
Health Benefits
The old record — seongmyeongja (菥蓂子). The Donguibogam lists it in the Herb section as 菥蓂子 under an old Korean name meaning the seed of the coarse shepherd's purse. Its nature is set down as slightly warm, its taste as pungent, with no toxicity. The entry says it grows everywhere and is the seed of the larger shepherd's purse, and records that the fruit is gathered in the fourth and fifth lunar months and dried in the sun. What was entered is the seed, not the leaf. What an old medical text wrote differs from how it is judged today.
Glucosinolates of the cabbage family. Compositional analysis confirms glucosinolates in cabbage-family plants and the enzymatic conversion, once the tissue breaks, into the compounds behind the pungency. The same work reports that heating halts the reaction. This is an analysis of composition.
The fatty acid profile of the seed oil. Repeated analyses report erucic acid dominating pennycress seed oil, which is why it has been handled as an oilseed crop. This concerns composition and is separate from the young leaves eaten as a green.
Nutrition
- Glucosinolates (present in leaves and seed) — the source of the pungency typical of the cabbage family
- Vitamin C (present in the young leaves) — a water-soluble vitamin
- Seed oil (erucic acid) (gathered in the ripe seed) — the fatty acid that dominates pennycress seed oil
The pungency of the cabbage family Pennycress carries the glucosinolates common to cabbage-family vegetables. When the tissue breaks, enzymes convert them into the compounds behind the pungency and the characteristic smell. Blanching settles that edge and takes the harshness with it. This entry stays with the compositional record.
How it differs from shepherd's purse Shepherd's purse (Capsella bursa-pastoris) hangs triangular pods and is lifted root and all for soup; pennycress hangs round, flat pods like coins and has larger, thicker leaves. Shepherd's purse smells stronger, pennycress less. Both are picked before the flower stalk rises.
The seed is not a green What the Donguibogam entered was the seed, not the leaf. Pennycress seed is rich in oil, dominated by erucic acid, and has been handled as an oilseed crop. What is eaten as a green is the young leaf; do not grind the ripe seed and eat it on your own initiative.
Blanching Thirty seconds to a minute in boiling salted water, then a cold rinse and a squeeze. Longer and the leaves collapse and the colour dies. Throw the blanching water away.
Pairings
○ Doenjang and perilla oil — Squeeze the blanched greens and dress them with doenjang and perilla oil. Enough pungency survives that the seasoning need not be heavy. A little minced garlic rounds the edge.
○ Batter — namul jeon — Toss the blanched, squeezed greens in pancake flour and fry them thin. The leaves are substantial enough to hold shape rather than break up. Frying softens the pungency for children.
○ Fresh-cooked rice — Lay the dressed greens over hot rice and mix. A little sesame oil and soy sauce is all it needs for the vegetable to lead. It is a dish of one short stretch of early spring.
△ Confusion with greater celandine — The real hazard when picking rosettes in early spring is greater celandine. Cut its stem or leaf stalk and a deep yellow sap runs out; that sap holds alkaloids and the plant is not eaten as a green. Pennycress bleeds no sap at the cut and its leaves are smooth. If yellow sap shows at the cut, discard the whole plant.
△ Sprayed ground and roadsides — Field and paddy margins are exactly where herbicide is applied, and roadside plants take in exhaust and dust. Ask the owner before picking and choose ground well back from the road. Wash what you pick several times in running water.
△ Not eaten raw — Pennycress is a green that gets blanched. The cabbage-family pungency can leave the stomach burning if a lot is eaten raw. Blanch in boiling water, rinse cold, squeeze dry, and throw the blanching water away.
Source: Donguibogam, Herb Section 菥蓂子