I have not grown Toy Choy, but do grow New Nabai. It will grow in late winter, early spring. Needs about the same conditions as radishes. Bolt quickly when temps rise . Does better in fall but still has a relatively short harvest window. They take a bout a month from seeding to harvest. These are small plants only getting about 6 inches so they can be planted at 4-6 inch spacing. They will thrive in any soil that a radish or a cabbage will.
I like Farmerdill's comparison to radish. They really are that simple and quick to grow. If allowed they will reseed all over the place too. I tend to like that..food without trying :0) I would experiment, I don't think you'd need a row cover. But since I've been growing them, the winters have been so mild, it's hard for me to say for certain.
They shouldn't need cover for temps- being in the cabbage family they really do best when it is cold. Warmth will make them bolt fast. My only problem was aphids. I found some live aphids yesterday on my overwintering strawberies! I guess they just hunkered down and spent the entire winter there!
My little ones planted in January are almost ready for harvest now. The early heat hasn't seemed a problem so far, but last year I was able to harvest them for a long time, I think up until June. They were in a spot that had afternoon shade, which may have helped. I saved seed to use next fall/winter, too.
I finally found my pictures of the Pak and Bok Choi I planted last fall.
This picture was taken on November 24.
I started them from seed in August.
As you can see in the picture they have started to bolt already. The Pak Choi (the purple one) never grew really big.
The Bok Choi taste really good, but very similar to Swiss Chard, in my opinion.
The Kale I started at the same time are bolting now ... so I had a much longer season from them.
Last spring I did plant both Bok and Pak Choi in my flower bed.
Have a look at the second picture: the Bok Choi bolted rather quickly (see the small yellow flowers) while the purple Pak Choi looked great.
Definetely the Purple Pak Choi is very decorative.
Also you can see that the spring Choi looks perfect, while the fall Choi has little holes in the leaves ... which is telling me that he likes to be planted in the spring here rather than in the fall.
I rather don't use any pesticide at all ...
I normally don't have any problem ... apart pill bugs ...
Actually I didn't mind who was eating the Choi , because they left alone all the other greens ... which I did like much more.
So it did work like a "catch crop".
Thanks for sharing your photos, drthor. Those purple ones look very nice. I bet they contain more anthocyanins than the green ones, too. Do they taste the same as the green box choi? If so, where did you buy the seeds?