I should think you could pull this off around 3-20, Sunny Dee-- especially if you have frost cover fabric and your plants are hardened off well. If Zone 5 is around the St. Louis area, when we lived there eons ago, I did put my vegetables out early but I didn't know about frost cover, or really much at all about anything! I remember crying when there was a heavy snow on my beautiful tulips.

This is a sleepy forum this time of year, but we all will get fired up soon. There are some very, very knowledgeable people here. Good luck and do let us know what you decide. I'd like to see a photo of your high tunnel project and your vegetables.
Sunny

The whole point of the cool-season things, such as coles, peas, spinach, lettuce is that they can take the cold soil. I wouldn't warm the soil but if you have something you can toss over them should an unseasonable cold snap hit, that would be good. If you know the planting date for your area, you are ahead of the game!

I am not really a vegetable gardener, but I do plant lettuce radishes, green onions etc. Except for the green caterpillars that love the cole crops, early vegetables are easier than hot weather vegetables. I am not using Bt anymore because I found out thuracide makes me sick, so probably a light weight bug protection row cover would be good to have. If Bt doesn't bother you, you need some for the worms on the broccoli. I cooked some once after washing it well, I thought, and worms floated to the top. Radishes like a particular soil. I have spotty luck with them. I put them in a good place last spring and with early rains they did well. I have not really figured out what soil they require. I think manure improved soil grows big tops with no radishes.

I am glad to see you on our forum and don't want to send you away, but ask Okiedawn. This is not about soil; it is about temperature; it is about cool season crops though. She is unbelievably thorough.

Here is a link that might be useful: temperature ranges for early season crops

Thank you all for your input! My extension service website said the rec planting date would be March 20-April 10 for most of the cool season crops I want. I just didn't know if I needed to do any other type of prep, etc. I don't want to ruin my plants.

Sunny Side, I'm in the Kansas City area and I will try to get a pic up at some point in March. :-)

Thanks so much for the link Helen, I plan on reading it tonight. It does look thorough!

Sunny D, even though some of us are in southern Missouri we are supposed to plant according to the northern Missouri zone. I guess because of the Ozark Mountain range we are on.

So we all will be planting about the same time.

Sunny Dee. I am south of you in z 6b and I raise at least 90 broccoli plants a year. I don't usually plant that early. If you go to the Ok forum and do a search of broccoli, you will get a lot of info. In a nutshell, pick an early variety. Packman is good. Allow 6 weeks minimum to get the plants started. I start the seed on a heated germination bench in MidFeb and plant after the first of April. Broccoli is a heavy feeder and likes a somewhat neutral soil. We use woodashes to sweeten the soil. But ag lime works too. If you can't use Bt, diatomaceaus earth will work to kill the worms. For me, broccoli comes off Memorial Day weekend, at which time I put most of it in the freezer.

It's too early for brussels sprouts.

You can download the University of Missouri Vegetable Planting Calendar
http://extension.missouri.edu/p/G6201

You can also call the Master Gardener Hotline 417-881-8909 ext 320
http://mggreene.org

Here is a link that might be useful: Missouri Vegetable Planting Calendar