Yep; edible rape

The usual spelling is Yu Choy and a google search shows that seeds are available from Evergreen or Kitazawa.
Rose-Marie

Yow choy means OIL Choy... they steamed the choy and pour some oyster sauce and some peanut oil on top, the vege you are eating most likely is Choy Sum... Yow means oil in Chinese... hope this helps

Agro Hai Tai has 8 types, my favorites so far are "Green 80 days" and "Welcome Hon Tsai Tai".

Autumn Poem from Johnnys Seeds is pretty good too.

Here is a link that might be useful: Agro HaiTai

Hon tsai cai is a green veggie with red stalks. Hon is red in chinese, cai is vegetable. I brought back a large seed package from China.

You cai is a green veggie with a yellow flower. There are eating types and a vegetable oil type that is grown for canola oil (correct me if i'm wrong). Someone from guandong gave me some seeds labeled cai xin. I planted them and they were you cai. Then someone told me they were you cai xin. Chinese people love that vegetable!

I suggest finding some chinese person (restaurant) who knows pinyin and write down the names correctly. My pinyin is not very good and phonetic would be yo tsai. I also got some ta tsai cai another person was talking about; spoon vegetable. It's very pretty to look at and watch grow. Got the seeds from the same Chinese guy.

I'm lucky I know an old chinese gentleman who is a very skilled vegetable gardener. Too bad he moved! His garden looked like a backyard garden in China, and I have traveled there frequently. I personally like the challenge of growing some weird vegetables from seed.

Does anyone know what USDA zone range(s) chinese veggies like 'Hon Tsai Tsai' are best to grow in? Plant in spring or the fall for best harvest results?

I do not think that Yow Choy means oil poured on top of the vegetables, since most vegetables taste better with some oil. Yow choy means oil vegetables because it is the same vegetable that produces canola oil (rape seed oil).