At our community garden, people have tended mustard greens (Brassica juncea) as a vegetable sometimes, other times as green manure, but mostly because it now just pops up as a volunteer. For those who had something else in mind, it is then a weed. Mizuna (Brassica rapa nipposinica) also pops up, self-sown from bolted Asian salad green plantings. Same with bok choy (Brassica rapa chinensis), that I have also found cropping up as a weed in a public reserves. In my herb garden, 3 volunteer heads of Chinese (napa or wombok) cabbage (Brassica rapa pekinensis) have also popped up this year after some was left to go to seed last year. This last one is the usual base for kimchi (spiced and salted Korean fermented cabbage), but all of the others can be used as well.
With a new sauerkraut crock (for German-style fermented cabbage, but Kimchi has the same process, just different ingredients), the previously sparsely used bounty of wild brassica greens has an invigorated welcome in my kitchen. A kitchen which also has the requisite fish sauce, red pepper and flaky salt, after a delightfully inexpensive shop at a local Asian grocer (Usagi-ya, Bondi Junction, where the Korean owner seemed thrilled to be kitting out a novice kimchi maker). I am still using some bought Chinese cabbage as at least half of a mix including other brassica greens and other vegetables, because that, along with the low temperature lactic acid fermentation is what defines kimchi (according to the Codex Alimentarius).
I have known I could easily start making kimchi, sauerkraut and other lacto-fermented food for some time (partly inspired by a great Tasmanian blog by a lady named Prue); just as I have known that it is tasty and very healthy; and I have known that an underutilised abundance of volunteer brassicas has being going to waste. I almost regret having taken so long to get to it, but for the enjoyment that I am getting right now out of the discovery of lacto-fermented foods.
I’m not really giving one. The internet abounds with kimchi recipes, but shop around. On the one hand there are many copied, cobbled and concocted recipes from enthralled newbies like me; and there is a lot out there from Koreans (especially expats and descendants in America) who are heir to centuries of the real deal; not to deny that perhaps there are fusions that take the heart of the latter and tweak to the palate of the former.
I have started from the straightest Korean version: Admittedly it required the right Asian grocer for me; and I accept that there are other chilli powders and fresh chilli options, different fermented fish sauces (like Vietnamese nam pla) and lots of flaky salt around; but there are versions of these ingredients made in Korea and exported to speciality vendors for kimchi by the masters of it. I’d suggest trying more authentic variations first, and then work out toward fusion and experimentation. Leaf brassicas other than Chinese cabbage, those that grow feral and volunteer included, are generally on the authentic side of the variation spectrum. There is a well resolved balance of salt, sour, spice, umami, sweetness and crunchy texture to the Korean tradition that is well worth buying into. And making the most of cheap and freely foraged vegetables fits well with it too.