The collard is not super fast but almost as hardy as Siberian kale ( not a true kale)

Agree about collards. Not super fast, but once they grow, you have a seemingly endless supply. They just don't quit.

Spinach and collards, will try both. Thanks!

Well, it all depends on when your last 10 hour day is. Here are some links for charts and finding out your last 10 hour day: http://www.johnnyseeds.com/growers-library/vegetables/winter-harvest-planting-chart.html  http://aa.usno.navy.mil/data/docs/Dur_OneYear.php 

Sorry, but that makes no sense. I've got a two-week window to plant winter crops?? Now, where I am now, the daylength is always longer than 10 hours, but when I lived in the PNW, I just planted winter crops when the summer ones were done. The daylength is some measure of sunlight, and if I live in an area where there are a lot of clouds, my plants will get vastly less sun than if it were clear.So daylength isn't really something you read off a calendar.

I can imagine there is some "optimality" to having a fixed schedule, but for the home gardener, it makes little or no difference. By far the main issue is freeze tolerance.

For people farther north it matters because after that last 10 hour day things virtually stop growing. It is proven science and makes complete sense. The chart is showing when the last few possible weeks to plant things are. I prefer to learn my information from the people who are doing this for a living and this is something that makes a big difference to many of those who use this information. You cannot plant something when there isn't enough photosynthesis for it to grow. If he is already having freezes he may not have enough time to put anything else in the ground.

Farther north than what, Alaska? I was at 45 degrees north latitude. Completely false that with shorter than 10 hour days things stop growing. Right now I have tomatoes that get 5 hours of sunlight, and they grow bonkers. Half as much photosynthesis as my neighbor down the street gets. I get more tomatoes than he does. Let's not confuse sunlight with temperature. Reference, please? People who learn this by doing it for a living are not home gardeners. They are commercial gardeners, and to them, optimal planting dates make a big difference. I respect that, but that's not my game

This is in regards to the shoulder season, low amounts of light combined with low temperature = slower growth and after your last 10 hour day things are virtually at a halt in growing. I have about 3 weeks where I have less than 10 hours of daylight and it does make a difference. I'm not going to argue with you on a forum. Look into yourself if you do not believe me.

Two problems with this idea. The main one is the presumption that that one calendar dictates optimal planting strategies for any given latitude. Yes, day length and calendar are related by precisely one thing - latitude. So what we're hearing here is that the planting schedule for Seattle, Washington ought to be the same as the planting schedule for Bismarck, North Dakota! That's nuts. Responsible planting schedules must take into account individual climates. Seattle and Bismarck have dramatically different climates, even at roughly the same latitude.

A related problem is that growth rate in plants is vastly more dependent on temperature than hours of sunlight. So a responsible planting calendar might instead be more dependent on mean temperatures or even degree-days.

No question that a serious market farmer will build a gardening schedule on the basis of all of these things. There is software available that does this. You dial in your zip code, and it takes into account day length, climate, and even soil properties. But yes, this forum is not the place to discuss those tools.

Johnny's has a lot of nice Excel calculators that do some of this as a function of frost dates, but even those are hugely simplified.

It is a little late to be planting kale, collards and chard - especially from seed. Do you have transplants? I'm in zone 5 near the Il/Wi border, and this is the third year we have been growing winter crops in a high tunnel. I planted the final seeds this last week - for spinach, tatsoi, and radishes. The goal is to have your plants mostly full sized by your last 10 hour day, as they grow incredibly slow after that. Make sure to get some row cover too! :)

Eliot Coleman's books will explain the entire thing. And he's in Maine and uses no additional heat,

I thought the post said growing in a greenhouse.so wouldnt that help esp a mild winter? just a asking

I'm in NH, zone 5, and have a high tunnel only covered in 6 ml greenhouse plastic. What amazes me is although inside at night is as cold as outside, the ground doesn't freeze. Inside warms up on sunny days. I have a thermometer in the high tunnel that I can read from my kitchen. I haven't put sides down yet because we are having unusually warm weather. I have the Eliot Coleman books and follow his farm on facebook as well as some other market farmers who grow near me in NH. Without using heating cables, spinach leaves can freeze but thaw when it gets warmer until it finally gets cold enough without additional protection to freeze kill. What the market farmers are doing is providing additional protection with covers of Agribon fabric. If things work out right, my favorite winter market has wonderful swiss chard in March. My suggestion is not to bother with heat cables but to use some kind of top protection. I have protected some plants like rosemary and variegated sage with Agribon and had them winter over. Rosemary made it through one winter but not the second. Purple sage had to be severely cut back this summer because it grew so well. It is not hardy in my outdoor garden. Some market gardeners are using some supplemental heat but I think it's mostly in early spring when they try to get a head start on things like tomatoes. Kale self seeded in my high tunnel as did cilantro so it starts growing in the spring. I haven't been providing Agribon protection for everything because voles have outwitted me and I decided not to try to overwinter beets and carrots inside. I have had some lettuce last as long as the holidays, die back from the cold and then some start growing again in the spring. Same for swiss chard.

I think the Eliot Coleman books would be very helpful for you. He explains the dormant period as the Persephone Period. Google it for more info.

daninthedirt, It is true, I have been following and growing in the winter for 12 years. Planting date and hours of sunlight make a huge difference. The difference in just a week can be the difference between a successful crop and one that doesn't grow. You are correct, some years are different than others, cloud cover and etc, but if you have never done it then please don't bash it. Growth doesn't stop, it slows down tremendously. Some years, with plenty of sunshine and mild weather things grow better. Every year around February 10th, the plants start taking off and growing more and more, that is when the hours of sunlight goes back above 10 hours.

To the original post: Spinach is a great crop to grow in the winter.