Japanese Negi cv. 'Shimonita'

Japanese Negi cv. ‘Shimonita’ harvested January 2020.

One of the most rewarding things we do here at Cypress Prong Farms is experiment with crops that normally are not seen in North Carolina. This could be anything from yukina savoy, an overlooked cold hardy green vegetable, to the gorgeous blush savoy heritage variety of cabbage  San Michele from the Trentino region in northern Italy. Or Spigariello, another import from Italy that is gaining favor in certain U.S. markets. Last year, we trialed a novel variety of Negi onion, ‘Shimonita’, and were completely taken by its stellar performance.

Over the years we have planted several types of Negi onion, all producing multi-tillered bunches of slender green stalks or “scallions”. The white, single-stalked Shimonita Negi we harvested in January sold out immediately at the local farmers market. This was a clue. It also piqued my curiosity about the large number of so-called “bunching” onions cultivated for food in Asia. What is the origin and taxonomy of these plants? Could they possibly fill a void in fresh, local winter produce in North Carolina and similar environments? How are they grown in their native lands?

The bunching onion, Negi in Japanese, has been cultivated for food since antiquity throughout Asia from Siberia to the tropics including Malaysia, Indonesia, and the Philippines. Botanists have ordained the Negi onion  Allium fistulosum in Latin nomenclature and positioned it within the Cepa subgenus that also includes other important edible Allium crops (Table 1).

Table1

nocaption

Allium fistulosum is a perennial herbaceous plant that is normally grown as an annual crop. Leaves and flower stalks are hollow in cross-section (Figure 1), an easily observable trait that differentiates Allium fistulosum from close relatives onion, garlic, and leek.

Negi onion has a sweet, distinctive flavor that compliments most other food ingredients. That is to say, unlike onion and garlic, it’s mild enough to be eaten raw and doesn’t overpower dishes prepared from it. Negi can be grilled or sliced raw in salads or pickled. In Japan, Fujime 2012 reported Allium fistulosum production on 22,700 hectares, ranking fifth in planted area behind daikon radish.  Demand for Negi in Japan is strong therefore production has gravitated toward highly mechanized operations:

 

In North America and Europe, Allium fistulosum is sometimes called ‘Welsh onion’ although it’s unrelated to Wales. The nickname ‘Welsh’ is actually derived from the German welsche, meaning foreign. The origin of this descriptor probably dates back to the Middle Ages when Allium fistulosum was introduced to western Europe via China. It’s stuck ever since.

A. fistulosum flower head and leaf cross-section

Figure 1. Allium fistulosum inflorescence and (inset) hollow or ‘fistulose’ leaf cross-section, a characteristic for which the plant is named.

To further confuse things, Allium fistulosum has many local names: in China, cong; in Taiwan, chung; and in Korea, pa. In France, it’s ciboule or oignon de Strasburg; and in English-speaking countries, Japanese bunching onion, Spanish onion, two-bladed onion, spring onion, scallion, among others. No doubt it’s acquired vernacular names in other languages, too. Here, I’ll reserve the proper name Negi because of my affinity for Japan. Back in the early 00s, I stopped over in Japan en route from Cambodia, staying in Ibaraki Prefecture with the family of a Japanese agronomist with whom I worked while at NCSU.  He introduced me to the local farming scene, which has an artisanal quality compared to the broad-acre farms here in North America. While there, I visited the prestigious Tskuba Science City, immersed in Japanese food culture, and learned how to make bokashi. Since then, we’ve raised many Asian vegetables on our farm in North Carolina, mainly for personal use. Tokyo and central North Carolina share roughly the same latitude and a similar climate, so most Japanese crops thrive here.

Back to classification, or what is termed taxonomy by botanists, the genus Allium is placed within the high-level monocotyledon, or “one” embryonic seed leaf division of flowering plants (the other division is dicotyledon or “two” embryonic seed leaves). When we think about monocots, grasses immediately come to mind. Grasses occupy the top spot in economic importance; it’s no exaggeration to say that a world without grasses would be an impoverished and uninviting place. On the other hand, it’s obvious that the genus Allium differs morphologically from, say, familiar grasses like maize (corn) wheat, and rice. I’ll describe some of these traits later, but the important thing to note is that the genus Allium is more closely related, genetically, to monocots like the agave, yucca, or amaryllis lily than grasses.

allium and wheat flowering

Alliums like Negi onion are monocots just like wheat and other food grains. But genetically, Alliums are more closely allied to lilies than grasses.

Recent surveys (Takhtajan, 1997; Friesen et al. 2006) have positioned the genus Allium within its own distinct family, the Alliaceae, and within the Order Asparagales named after, you guessed it, the humble asparagus. Some classification systems place Allium within the lily or amaryllis family, so the consensus, at least among specialists who wrangle over these things, is far from settled.  After the grasses, the Asparagales is the second most agriculturally important monocot order. The progenitor of Allium fistulosum is not certainly known but evidence suggests it may have originated in northwestern China where a closely related wild species A. altaicum commonly occurs. The global diaspora of Allium fistulosum, like all Alliums, has closely followed on the heels of human migration for good reasons: it’s an adaptable, savory, and easy to grow culinary ingredient with long-appreciated medicinal properties.

In Japan, Negi onions are further classified into three major groups according to ecological and utilization preferences (Inden and Asahira, 1990). The ‘Kaga’ group is grown in the coolest parts of Japan mainly for its white (etiolated) stalks;  the ‘Kujo’ group in the warmest parts of Japan, and is favored for its leaf production; and, the ‘Senju’ group, which is intermediate in preference and grown for its white stalks in central Japan, near Tokyo.  A fourth group, the ‘Yagura-Negi’ is a winter dormant crop cultivated mainly in home gardens in warmer parts of Japan for its green leaves. Negi onion cv. ‘Shimonita’ belongs to the Kaga group. Other Negi onions we’ve tested include Tokyo Long White and He-Shi-Ko, both tillering types.

Here, we’ll pause to explain some of the terminology surrounding onion traits in the Allium family. Generally, two types of Alliums are distinguished: bulbing and non-bulbing. Bulbing is a trait characteristic of onion, pearl onion, shallot, and garlic. Whereas, Negi onion, chives, and Chinese chives do not form bulbs in the true sense. True bulbs are made up of many overlapping layers of specialized swollen leaf sheaths and modified bladeless leaves (scales); the true stem is a small disc of tissue, sometimes called a basal plate, located at the interface between the leaf sheaths and roots (Figure 2a).  Some diagrams, like Figure 2a, refer to sheathing leaf bases as “scales” while others say “bases”. This nomenclature is confusing but anatomically, they are all specialized leaf sheaths. Non-bulbing onions share similar anatomical features but the leaf sheaths do not accumulate carbohydrates. Therefore, sheaths appear flattened and lengthen longitudinally along the stalk axis. When the sheaths overlap one another they form a tightly packed, stalk-like pseudostem. The pseudostem is the principle edible part of non-bulbing Alliums like Negi onion and leeks (Figure 2b). A slight bulb-like thickening of the pseudostem at the base may occur in some Negi onions while other cultivars have edible leaves and stalks.  For brevity, the word ‘stalk’ is used herein in the vernacular sense to mean pseudostem.

Allium duplex image

Figure 2(a) Onion bulb with principle parts labeled. (b) Classical illustration of Allium fistulosum with principle parts labeled. The scape is the flower stalk. The spathe is a protective sheath of tissue surrounding the immature inflorescence.

Negi onions are exceptionally well adapted to a wide range of climates and ecological situations. We can attest to this fact here in North Carolina. In the spring of 2019 several plantings of Negi ‘Shimonita’ were established on a Helena sandy loam soil on our farm. Two prolonged dry periods coupled with high temperatures occurred from mid-May to early June, and again in September. The intervening time was variably wet or dry but hardly optimal for crop growth. Much of the dryland corn in our area was severely scorched. Our sweet corn plots required daily sprinkling and even then, stress was evident in the smaller ears and kernel rows per ear harvested. But we didn’t irrigate the Negi onions the full season. Aside from a pre-plant sprinkling of 10-10-10 fertilizer per recommendation and two hand hoeings, the crop received no coddling. Despite this neglect, Negi ‘Shimonita’ exhibited few signs of stress. By October, we had a mature crop of fat, succulent Negi stalks ready to harvest. Rana and Mor (2018) reported the widespread cultivation of Allium fistulosum in sub-Saharan Africa. They noted that established plants are tolerant of heavy rains, drought, and hot and humid conditions near Brazzaville and Kinshasa in central Africa. So, it seems that our experience with the Negi onion here in North Carolina validates the plant’s resilient nature under duress. Still, there are many challenges to growing Negi onion on a commercial scale. Most of these concern the rather specialized agrotechniques needed to grow the crop.

The YouTube video up top portrays a fair representation of techniques applied to Negi production by Japanese farmers. Per the video, it’s a highly specialized operation requiring many different pieces of machinery (please ignore the pesticide sprayer in that video, that’s not how it should be done!). We have none of that here for obvious reasons. Few people in North America know about the white stalk Negi onion so there’s little demand for it, commercially, and virtually no infrastructure devoted to production outside the diminutive green bunching onions that populate supermarket produce shelves. That is a shame. We believe a strong market for Negi onion could be developed in North Carolina and are taking small steps at CP Farms in that direction.

float bed tray

Figure 3. Float bed tray with Negi onion transplants.

Our first crop was produced from transplants raised in float-bed trays in a hoop house similar to that of tobacco (Figure 3). The reason for this has to do with the growth habit of the Negi onion. Direct-seeded onions are relatively slow to germinate (7-10 days at 15° C) and the delicate seedlings compete poorly with weeds. Pre-plant incorporated herbicides like Prowl (pendimethalin) would help control annual grasses and some broadleaf weeds in onion fields; however, the use of this herbicide in North Carolina is restricted. And chemical weed control certainly wouldn’t fly if you’re growing organic. That leaves cultivation as the only option for weed control so it’s important for onion transplants to hit the ground running. The video up top is a bit misleading, though. Transplanting looks to be done on ~30 cm rows, but later clips, particularly those execrable sprayer shots, show row spacings much wider than 30 cm apart. So, it’s not clear if the techniques in this video depict a single continuous operation or a mélange of clips sourced from different farms growing Negi onions for different end-use in Japan.

One peculiar agronomic trait associated with Negi onion is the tendency for leaf sheaths to elongate as the earth is mounded up around the plant. Earthing up or “hilling” the crop produces the long blanched onion stalks favored by Japanese consumers.  In the Japanese technique, earthing up is done two or three times per season, creating 30+ cm high near-vertical ridges. Exactly how these ridges are built up is unknown; obviously a special tool is employed for this but I’ve never seen it in operation. Leaf sheaths vary in length according to Negi cultivar: cv. ‘Shimonita’ of the ‘Kaga’ group are not so long whereas, cvs. ‘Hakusyu’ and ‘Kuronobori’ of the ‘Senji’ group grow very long. Saying that, selecting cultivars for sheathing ability under ridging is certainly a worthy goal for plant breeders.

Earthing up Negi onion in Hawaii

The practice of earthing up Negi onion stimulates the growth of leaf sheaths.

We put ‘Shimonita’ transplants in a shallow furrow and covered them with soil via hand hoe since we have no specialized earthing up equipment. I believe it would be possible to rig up plow sweeps to cut a furrow and disc hillers for in-season ridge building, but this is still a far cry from the advanced Japanese techniques depicted in the video. Uyeda et al. (2016) at the University of Hawaii at Manoa evaluated 20 commercial Negi onion varieties for fresh weight and stalk length, including cv. ‘Shimonita’. Plant beds were prepared by cutting 25-cm deep furrows with a Honda walk-behind tiller equipped with plow sweeps followed by hand transplanting, similar to our own efforts. The width between plant rows was 1.2 m to allow for mechanical hilling every three weeks. The authors do not say how hilling was applied; my guess is that they tracked the same Honda walk-behind tiller down the plant interrows.

Aside from earthing up, Negi onion is not particularly demanding in terms of cultural preferences. According to Warade and Shinde (1998), a soil pH between 5.7 and 7.4 is suitable for Negi onion (6.0 to 6.5  is recommended in North Carolina, see the online 2020 Manual). The same authors report fertilizer totaling 200, 150, and 175 kg/ha of N, P, K, respectively, applied three to four times per growing season. This is on the high end recommended for green onion production by NC State University Cooperative Extension, but we didn’t apply anywhere near this amount and still made a decent crop. More research on cultural practices for white stalk Negi is needed. We didn’t detect any insect or disease problems in our Negi plots although sources indicate attacks by numerous pests including the infamous onion thrip,  vector of tospoviral agents tomato spotted wilt virus (TSWV) and iris yellow spot virus (IYSV) (Warade and Shinde, 1998; Brewster, 2008) have been reported. TSWV is prevalent here in North Carolina and IYSV on the rise globally. Both diseases are highly damaging to Alliums.

We’ll evaluate Negi onion cv. ‘Shimonita’ again this year.  The seed is readily available in North America from multiple sources; we’ve procured Asian vegetable seed from Kitazawa over the years and have always had good luck.  You can also easily save your own seed. I’d like to see more commercial white stalk varieties from Japan, even F1 hybrids, made available here in the U.S. However, that won’t happen until demand grows. At CP Farms we intend to do our part to see that it does.

Further Diggings

Brewster, J.L. 2008. Onions and Other Vegetable Alliums. 2nd ed.  CABI International Press, Cambridge, MA.

Friesen, N., Fritsch, R.M., and F.R. Blattner. 2006. Phylogeny and new intrageneric classification of Allium (Alliaceae) based on nuclear ribosomal DNA ITS sequences. Aliso Vol. 22: Issue 1, Article 31. Available at https://scholarship.claremont.edu/aliso/vol22/iss1/31/ (verified 11 May 2020).

Fujime, Y. 2009. Introduction to some indigenous vegetables in Japan. Available at: https://journals.ashs.org/hortsci/downloadpdf/journals/hortsci/47/7/article-p831.pdf (verified 11 May 2020). An accessible, well-written and illustrated piece on Japanese vegetable foods and food culture.

Inden, H. and T. Asahira. 1990. Japanese bunching onion. In: Rabinowitch, H.D., and J.L. Brewster (eds). Onions and Allied Crops. Vol. III. Biochemistry, Food Science, and Minor Crops. CRC Press, Boca Raton, Fla.  Chap. 8.

Rabinowitch, H.D., and L. Currah. 2002. Allium Crop Science: Recent Advances. CABI Publ. New York, NY.

Salunkhe, D.K., and S.S. Kadam. 1998. Handbook of Vegetable Science and Technology: Production, Composition, Storage, and Processing. Marcel Dekker, New York.

Rana, M.K. and H. Mor. 2017. Welsh onion. In: Vegetable Crop Science. Rana, M.K. (ed). Taylor & Francis, Boca Raton, Fla. Chap. 7.

Takhtajan, A.L. 1997. Diversity and classification of flowering plants. Columbia University Press, New York, NY.

Tsukazaki, H., Honjo, M., Yamashita, K.I., Ohara, T., Kojima, A., Ohsawa, R., and T. Wako. 2010. Classification and identification of bunching onion (Allium fistulosum) varieties based on SSR markers. Breed Sci 60. https://doi.org/10.1270/jsbbs.60.139

Uyeda, J., Fukuda, S., and J. Sugano. 2016. White stem Negi onion variety trial. Preliminary observations. University of Hawaii at Manoa College of Tropical Agriculture and Human Resources.  Available at https://gms.ctahr.hawaii.edu/gs/handler/getmedia.ashx?moid=1603&dt=3&g=12 (verified 11 May 2020).

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