Yu Choy Sum
Brassica rapa ssp. parachinensis
- WHAT IS IT? – A leafy green member of the diverse Chinese cabbage group. Choy sum, while technically a Chinese cabbage, does not form heads, but instead forms bunches of long, thick stalks. Choy sum, literally ‘vegetable heart’ (heart in this case meaning stem), is a reference to the long, delicately flavoured stems typical of this vegetable. It can actually refer to any young green vegetable, but it is most often applied to this one (yu choy).
- SEASONALITY – Available year-round, but best in cooler months.
- FLAVOUR PROFILE – Mild; Green/Sweet/Bitter
- OTHER NAMES – Chinese flowering cabbage, Chinese mustard, Chinese oil vegetable; yu choy, yau choy (sum) (Cantonese transliterations commonly used in English); yóu cài (xīn), cài xīn (Mandarin). Note that some of these names are used in reference to closely related bok choy as well.
BASICS & HOW-TO
Yu choy sum is not quite as well-known as some of the other Chinese green vegetables, but it’s incredible easy to use, versatile to cook with, not to mention delicious. This has made it quite popular in China (especially in the South), and generally fairly easy to find at Asian grocery stores.
Technically, yu choy and (yu) choy sum could be sold as different vegetables; choy sum refers to the young, tender vegetable hearts, but yu choy can be grown to produce a larger, less tender vegetable. As a general rule, the younger ‘choy sum’ stalks are preferred, but larger plants are similar in taste and use.
Choose bright, fresh looking yu choy sum without any obvious dents in the stems or discoloration in the leaves. Try to avoid stems that look particularly floppy or wilted. Avoid leaves with yellow edges – these will often be bitter. Try to avoid yu choy sum with lots of small holes or chewed sections on the leaves as these may be signs of insect damage. Small flowers, though less frequently found on the small tender stems, are normal and edible.
If you’re choosing large yu choy, the same selection methods apply, though the leaves may look a little rougher and flowers are more likely to be present on the stems. This is normal, and the flowers are perfectly edible.
Yu choy sum is extremely easy to prepare. Simply wash the leaves and stems gently in cold water. Make sure to wash around the base of the stems carefully, getting in between the stalks where dirt can build up. You may wish to trim the ends of the stems off if they’ve become a little dry.
Yu choy sum, while similar to gai lan in many respects, tends to be more tender. As such, the stalks are often cooked without trimming or cutting into smaller pieces. If desired, choy sum stalks and leaves can be separated for individual cooking. If you’re cooking with older yu choy, the larger, firmer stems may require separation from the leaves and trimming to size or longer cooking.
Yu choy (sum) can be cooked in a variety of ways. As with many other Chinese vegetables, quicker cooking methods tend to be preferred. Yu choy sum stems tend to be tender enough that they can be cooked along with the leaves. With older yu choy, you may want to cook the stems separately (e.g. by adding them to a stir fry first) in order to avoid over-cooking the leaves. For both yu choy and yu choy sum methods like blanching or stir-frying will often yield the best results. Braising can yield good results as well, but make sure not to overcook the stalks, as this will reduce them to mush.
Unless you plan to use it very soon, yu choy sum should be stored unwashed in the crisper section of a refrigerator, ideally in an open or breathable plastic bag. It will keep well for 3-7 days, depending on how fresh it was at the outset.
If you have excess yu choy sum you can clean, chop, and blanch it for 2 minutes, dunk it in very cold water, then drain and immediately freeze. It will freeze well for a year, and can be added to soups, stews, or dumplings.
First and foremost, it should be pointed out that yu choy and yu choy sum are already somewhat different, but can substitute for one another. Second, it’s worth noting that you may encounter other green plants grown or sold under the name ‘edible rape’ or ‘oil vegetable.’ These are very close relatives (or even the same plant), and can stand in readily. That being said, they are not generally available on a large commercial scale, though you may find them at some farmers’ markets and Chinese markets.
Gai lan makes a respectable replacement, thought it has a thicker stem (which requires longer cooking or cutting into smaller pieces) and a more broccoli-like flavour. Bok choy makes a good replacement from a flavour perspective, though it usually lacks some of the mustardy flavour of yu choy sum and a has different texture when cooked.
Outside of the Asian vegetables, rapini (ala broccoli raab/rabe) makes a good stand in. Like gai lan, it tends to be a bit tougher and more flavourful, and its bitterness is more pronounced. Interestingly, rapini is actually quite closely related to yu choy – both are edible members of the ‘rape’ group (Brassica rapa).
Yu choy sum is a fairly versatile green vegetable, generally used cooked. It tends to show up most often in Asian (especially Chinese) dishes, but it can be adapted to a wide variety of cuisines. It is occasionally salted, pickled, fermented, or otherwise processed to produce highly flavourful side dishes and ingredients.
Yu choy sum is mild enough that it can’t really be said to pair particularly strongly with any one food or another. Instead, it’s mild and versatile enough to use with an extremely wide range of foods. It generally doesn’t headline a dish, instead acting as a side or accompaniment to some sort of main dish or sauce. The fact that the stalks are much softer than many other Chinese greens (e.g. gai lan) makes it popular as an accompaniment to braised or slow cooked meat dishes.
Yu choy (i.e. older, less tender plants) are very similar, but are often less tender and stronger in taste, with a more distinctive mustard-like heat. This makes them somewhat less versatile, but even these factors can be diminished during cooking.
There doesn’t tend to be much variety in commercially available yu choy (sum), but there are some interesting varieties available to home gardeners and in the occasional farmers market. There are some reddish/purple-stemmed varieties available, as well as some leafier varieties with more prominent flowers.
To see all the diversivore recipes using yu choy sum, click the navigation bar at the top of the page, or simply follow this link.
Yu choy sum is extremely high in Vitamins C and A, moderately high in calcium, and low in calories.
There is no GMO yu choy sum in the food supply, however it is a monitored crop on a ‘contamination watchlist.’ This means that yu choy sum is considered to be at some risk for accidental contamination through cross-breeding with GMO relatives that are in commercial production. All vegetables from this species (Brassica rapa) as well as several related plants in the mustard family are on this watchlist, and are tested regularly by non-GMO watchgroups.
Yu choy sum is a member of the family Brassicaceae (the cabbage and mustard family), a group often referred to as the cruciferous vegetables. Members of this family contains chemical components called glucosinolates, which are responsible for giving these plants their distinctive, pungent scent. These compounds have interesting effects in the human body. At normal levels (i.e. those achieved by consuming cruciferous vegetables as part of a balanced, vegetable-rich diet) they are believed to have some cancer-protective benefits. At unusually high levels (i.e. those achieved by eating extreme quantities of raw cruciferous vegetables, on the order of kilograms per day) , glucosinolates can interfere with thyroid function, causing serious illness or even death. While there is at least one reported case of a person effectively overdosing on bok choy (an elderly diabetic woman who ate 1-1.5 kg of raw bok choy per day), it is worth noting that including yu choy sum in a normal, balanced diet is far more likely to have positive health benefits than negative ones. If you have a thyroid condition and you have any questions about eating any cruciferous vegetables, consult with a medical professional.