Yukina Savoy (Brassica rapa variety). The photo was taken in January 2018 after several nights at 16°F (-9°C).

Across a broad swath of North America, January isn't prime time for outdoor plants, nor for veteran dirt hogs dreaming of tilling the soil, sowing seed, and coddling the various tribes of the vegetable kingdom. North Carolina is not exempt from this seasonal hiatus despite its usually mild winters. Witness January 2018: opening with an icy blast of polar vortex strong enough to spawn what is being called a bomb cyclone (!), further north, thankfully far removed from my perch. Still, poignant traces of leafy green bolt skyward in the Carolina winter garden undaunted, longing to capture the sun's rarefied gleam. One such leafy green is Yukina Savoy, a relatively obscure, hardy Asian vegetable that can withstand freezing temperatures, every bit as good as southern mainstays like collards and kale.

Yukina Savoy is a member of the Brassica, or mustard, family, a large, diverse group of dicotyledon (two-seeded) plants that includes many that play significant economic, scientific, industrial, and agronomic roles. Readers are probably familiar with canola oil on supermarket shelves. But did you know that canola comes primarily from two rapeseeds: Brassica rapa and B. juncea, both Brassicas and close relatives of our very own Yukina Savoy?

How about biodiesel? Yes, rapeseed can do! Further, the Brassica Aribidopsis thaliana has achieved worldwide status as a "model" plant for genomic studies, while the spicy horseradish or wasabi dressing on your sushi platter derives respectively from the grated root of two Brassicas, Armoracia rusticana and Eutrema japonica. And, don't forget the obligatory hot dog and pretzel topping, mustard, from the seed of three brassicas: B. juncea, B. nigra, and B. alba, a.k.a. yellow, brown, and white mustard. No doubt about it: Yukina Savoy belongs to an elite multipurpose family of plants, many with tremendous untapped or underexploited genetic potential. Life without the Brassicas would mean a world without many crops and the model plant systems that have played a crucial role in advancing genetic progress in agriculture.

According to Warwick et al. (2006), currently, about 338 genera and 3,709 species are recognized in the Brassica family, distributed worldwide on every continent except Antarctica. Familiar cultivated species, all interrelated, include cabbage, broccoli, cauliflower, collard, kale, kohlrabi, Brussels sprouts (variants of B. oleracea or "cole" crops); turnip (B. rapa), and the rutabaga or swede (B. napus), arising from a marriage between cabbage and turnip; the humble radish and sleek Japanese daikon (R. sativus); and pungent watercress (Nasturtium microphyllum). The official family name is the Brassicaceae, often abbreviated Brassica, even though many members do not belong to the genus Brassica. Some varieties have sharp, pungent, or spicy flavors due to chemical compounds produced in the plant, such as glucosinolates, myrosinase, and isothiocyanates. Some of these compounds are being studied for their anti-cancer or pesticide potential, while others may be harmful in high concentrations (but they're all natural!).

The Brassicas can be instantly recognized in the field by their unique flowers: four yellow petals arranged in the pattern of a cross from which their older botanical name Cruciferae (i.e. crucifix) was derived, and fruiting body, a dehiscent (self-exploding) capsule, or silique, seen in the picture below. Exceptions to petal color include white, pink, and purple. These unique characteristics enable the identification of Brassicas at a glance, in a gestalt-like way, even without knowing their exact names.

Brassica flower and seed capsule. Image: UCLA Publ. 4030.

The tribe Brassiceae, of which Yukina Savoy is a member, consists of about 50 genera and 230 species (Al-Shehbaz et al., 2006). Technically, Yukina Savoy belongs to Brassica rapa, field mustard, a genus that shows considerable variation in growth form and includes widely cultivated varieties, or so-called "cultivars". Field mustards are all herbaceous annual or biannual plants, with cultivated varieties generally being placed in four major groups (after Warwick et al., 2006):

• Chinensis: Those forming non-heading upright compact clusters of leaves with fleshy smooth stems. Major cultivars, all long domesticated in China and Japan, include bok choi and pak choi. Whole young plants are harvested for their green leaves and fleshy green or white stems. They are common ingredients in stir fry, soup, and noodle dishes.
• Pekinensis: Known as nappa, hakusai, pe-tsai, choy sum, Chinese, or celery cabbage, forming a tight or loose cluster of leaves with fleshy winged stems. These varieties also have a long history of cultivation in China, Japan, and Korea, and are favored for making the fermented Korean specialty dish kimchee.
• Nipposinica: mizuna, mibuna, and komatsuna are Asiatic non-heading leafy vegetables with multiple tillers and either pinnate (lobed) or smooth leaves. These varieties are also common ingredients in Asian dishes.
• Narinosa: Asiatic non-heading leafy vegetables with a flat rosette of numerous small leaves. Major cultivars: Chinese flat cabbage, tatsoi, broad-beak mustard, and Chinese savoy.

Where does Yukina Savoy fit in this scheme? That's a good question. Yukina Savoy has dark green, spoon-shaped, puckered leaves affixed to smooth white stems arranged in an upright rosette in mild weather, becoming somewhat flattened in colder weather. In this regard, it resembles a larger version of tatsoi but is classified as the pekinensis "loose head" type by the Kitazawa Seed Company in Oakland, CA, my seed source. Major Brassica references do not even mention it. Nor do I have the faintest idea how the European word 'savoy' became attached to an Asian plant; perhaps someone thought it resembled the crinkly savoy cabbage leaves? Regardless, Yukina Savoy is a nutritious, tasty addition to the winter table.

Production statistics for Yukina Savoy are hard to come by. The crop is not grown on a large scale anywhere in North America. Reports by Grahn et al. (2015) from Washington State, and Matheke et al. (2006) in Alaska, suggest small- to moderate-sized farms and home gardens are the primary production venues. A recent trip to H Mart, the mega-Asian grocery chain, did not find Yukina Savoy among the plethora of exotic vegetables (edible banana flowers, anyone?) cramming the shelves and aisles.

Mature Yukina Savoy planting. Photo taken November 2, 2017.

Yukina Savoy is easy to grow. Here at Cypress Prong Farms, we directly seed it in late summer with sharp-head Jersey Wakefield and San Michele cabbage transplants, as well as broccoli, collards, kale, bok choi, daikon, turnip, and Chinese cabbage. It's a fast-growing crop, reaching about 12" tall after about 45 days, although baby plants may be harvested in half the time. The large, upright leaves are deep green in early fall, turning dark bluish-green after several nights below freezing. Older leaves tend to die back after a hard freeze, leaving a central rosette as pictured at the top. Plants are harvested by cutting off the entire rosette at the base. Any surplus Yukina Savoy we glean is donated to the local farmer's market, where it serves as a conversation starter-cum-sales pitch.

Kitazawa claims the plant is heat-resistant, although we have never attempted growing it, or any Brassica for that matter, during summer here in North Carolina. Experience has shown that this usually does not turn out well, regardless of vendors' claims about heat tolerance. Here, fall-planted Yukina Savoy will bolt in early spring, conditioned by vernalization, day length, temperature, or a combination of these factors (bolting in Brassicas is a complex trait). Even in chilly Alaska, Matheke et al. (2006) reported May 23 Yukina plantings had bolted. In any case, by late spring, we have moved away from the cool-season stuff to the more voluptuous nightshades and invigorating cucurbits, and have little need for it.

So, there you have it: The Brassicas and Yukina Savoy in profile. Did I mention that all this scribbling and pushing keyboard buttons has worked up a hearty appetite? Wouldn't this be a good time for a bowl of hot miso noodle soup with Yukina Savoy, Negi onion, and turnip root?

Grab your chopsticks, cue the Savoy Orpheans for a dose of vitamin M (music), and you've got a banquet for January bomb cyclones!

Further Diggings

Al-Shehbaz, I.A., Beilstein, M.A., Kellogg, E.A. 2006. Systematics and phylogeny of the Brassicaceae (Cruciferae): an overview. Plant Syst. Evol. 259, 89–120.

Anjum, N.A., Gill, S.S., Ahmad, I., Pacheco, M., Duarte, A.C., Umar, S., Khan, N.A., Pereira, M.E. 2012. The Plant Family Brassicaceae: An Introduction. In: The Plant Family Brassicaceae Contribution Towards Phytoremediation. Springer Dordrecht, pp. 1–33.

Grahn, C.M., Benedict, C., Thornton, T., Miles, C. 2015. Production of Baby-leaf Salad Greens in the Spring and Fall Seasons of Northwest Washington. HortScience 50, 1467–1471.

Warwick, S.I. 2011. Brassicaceae in Agriculture. In: Genetics and Genomics of the Brassicaceae. Springer New York, pp. 33–65.

Matheke, G.E.M., Hanscom, J., Holloway, P.S., and Gardiner, E. 2007. Vegetable Trials 2006. AFES Variety Trial 2007-2. VT 2007-02. (last access: Jan. 5, 2018)

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