I know it's not heat tolerant at all. It's aka argula here. You can get a good size packet and plant it in rows 2 weeks apart like 3 or 4 times. Then you just cut down one of your rows at a time to harvest, which should resprout for you so you can reharvest a few weeks later. By staggering them you always have some going. You can plant it now, like most any other lettuce.

I love its nutty taste also. I grow it most winters though I don't have any growing right now. How long into the year you can keep it going all depends on the weather but you can grow it the same way you grow lettuce or spinach.

If you want it soon you need to sow the seed in flats inside the house and then move the flats outside during the day to harden off the seedlings before you plant them in the ground. With December being the darkest month of the year not much will sprout or size up this month. Seeds sown earlier in the year that have already sprouted could be nice and full by now and you could harvest from them but they don't do a lot of growing during December. If you sow seeds indoors and get them outside by March you should be able to harvest many salads until it gets too hot (usually mid June).

Check any garden center for Rocket or Arugula seeds.

I planted mine out too late last year and didn't get a lot of growth over the summer, but to my surprise it didn't flower and set seed until late fall. I'll probably start it again in Feb. I bought seed for two different kinds in the grocery store in Italy last summer. I think one is similar to what they sell here in the US (Eruca sativa), but the other has more finely cut leaves and a sharper taste and is probably either the native Italian E. sylvatica, some species of Diplotaxis, or what they sell in the states as 'Sylvetta'. Whatever it is, that's the one that was more heat tolerant for me this year.

I planted in early October a Mesclun mix that I bought from Logan's in downtown Raleigh. This mix includes Arugula, Mizuna (which I love) and various varieties of lettuce and Asian greens. All are doing well under shade cover and I pick enough leaves for salads several times a week. Personally, I find Arugula alone too strong and prefer it mixed with baby spinach or red leaf lettuce. Park Seed has both mild and strong flavored Mesclun mixes and I believe that the latter is the one that includes Arugula. I recently planted another bed with a mix of the Mesclun seed and spinach in alternate rows, but after 3 weeks have not seen a single seedling even though the bed is protected with a plastic cover. So if you want to grow some in a cold frame during this winter, sewing the seed in flats and starting them inside will speed up the process. It seems very cold hardy if you can keep the frost off of the leaves.