While I'm not positive, you've gotta be in zone 4. I'm in zone 5 in Central Illinois - and you are hundreds of miles north of us.

Anyways, I think May/April may be a bit too early for planting cool weather veggies.

The cool weather veggies will typically survive fine as long as temperatures do not go below freezing. Some even can stand a very light frost - but a hard freeze, and that is out.

In my zone, a 50% chance of frost can occur after April 23 with only a 10% chance of frost occurring after May 11th.

For cool weather crops, I wouldn't put them out more than two-three weeks before that 10% chance of frost occurring date - unless you take precautions to make a hoop house, use frost blankets, or some other kind of protectant that will help to insulate your crops from a killing frost.

Here is a link that might be useful: BsnTech Gardening Blog

Your soil temps, not your air temps best determine when cole crops and other hardy cool weather crops can be planted. Linked a planting chat below for you and you'll note that once soil temps reach 40 degrees and remain there for several days most cool weather crop can be planted. That is often 3-4 weeks before your last frost date. That is part of what they mean when they say "plant as soon as the soil can be worked in spring".

While some of the semi-hardy ones may need a bit of hard frost protection/cover now and then, most will tolerate light frosts and even snow with little problem.

You might also ask the gardeners over on your regional and/or state forum here what their planting times usually are for various crops as they can be the best source of regional and local info. They can also clarify for you exactly which zone you are in (AFAIK Boyne City Michigan is zone 4) and exactly when your last frost date is.

Dave

Here is a link that might be useful: Soil Temp Planting Chart

I'm not real familiar with Zone 4 or 5 but I did find this websit from the University of Minnesota Extension office that might be helpful. http://www.extension.umn.edu/info-u/plants/BG437.html

I'm in Maryland and I'll be planting my broccoli, cauliflower, brussels sprouts and lettuce around the middle to end of March. The summer stuff (tomatoes, etc) will be planted about May 10th.

According to the link given the following cool weather vegetables are considered "hardy". These are:

broccoli, cabbage, kohlrabi, onion, lettuce, onion,
peas, radish, spinach, and turnips.

The semi hardy are beets.

Now broccoli, cabbage, kohlrabi, and onions don't apply to me as I won't be growing them. However I will be growing peas, lettuce, spinach, a white radish (asian variety, also known as daikon; longer in length, takes longer to mature),
and a Japanese variety of turnip (white, no purple top and is quicker to mature than typical turnip varieties), and spinach.

I didn't know there was a difference in hardiness with some cool weather veggies depending upon what the cool weather veggie is. I thought all cool weather veggies were considered hardy and could be planted earlier than warm weather veggies as a result, especially since all cool weather veggies grow best in cool weather.

What is the difference between hardy and semi hardy?
I know that tender veggies cannot grow in any type of cool weather and aren't tolerant of frost at all.

What is the difference between hardy and semi hardy?

As defined in the article linked above:

Hardy Vegetable Crops are vegetables that will grow with daytime temperatures as low as 40 degrees and survive a frost. I have even seen them survive snow.

Semi-Hardy Vegetables Crops are vegetables that will grow with minimum temperatures of 40o to 50o, but are less tolerant of a frost. So they can either be planted a bit later than hardy ones when the chance of frost is less or covered if frost threatens.

Hope this helps.

Dave

FRom my exerience, cool crops can survive a deep freez down to 15F. but that does not mean that they will grow in such a cold weather. But once lows are above 32F and highs approack mid 40sF, they will resume growing, slowly.

To get a head start you can start your favorite cool crops inside and transplant the seedling in the garden when your temps range is better than 32F -45F.

Cool crops That I have:
parsley, sage, thyme, rosemary, onions, shallots, cabbages, kohlrabies, lettuce, aurugulas, chinese cabbage, leeks, cilantros,and garlics. These are actually things that I have and they have survived 15F. There are many more like mustard greens, broccolies, kales , peas , etc.
Add; radishes and spinache for real early spring (no freezing)

I am blessed to live in zone 9, but I've been harvesting from my greenhouse all winter. Some of the varieties I'm growing would be good candidates for those in other hardiness zones, but just planted later owing to the colder climate.

Here are some of the more unusual veggies to consider: Kale, Chard, Miners Lettuce, Mache, bok choi. I've been covering winter gardening in my blog and there are pictures of some of these on the site if you want to look. See below link.

Here is a link that might be useful: Winter vegetable gardening

Well unfortunately most of the cool weather veggies I'm growing are root veggies (turnip, beets, and radish). I've heard that root veggies are best direct sown and don't transplant well at all.

I can't start them inside unless I grow them in the container they'll be growing in outside for the duration of the season. Unfortunately I don't have the space to do this; even I did I don't know how I'd set it up growing the seedlings in large containers because seedling transplants are normally grown in peat pots or cells.

What constitutes as "early spring" in the northern part
of the lower peninsula in Michigan (in regards to gardening). Last season I planted stuff I was late with planting because I didn't arrive in Michigan until about the middle of May.

I'm guessing that any leafy green thing (lettuce and spinach are what apply to me) can be grown in early spring? I also heard peas can be grown in early spring too?

Anything that is grown from seeds can be transplanted There are degrees of eas and difficultie and knowing how to do it.
What you can do is to sow the seeds directly ,as soon as the ground is workable(not frozen). Then you will wait and wait. The seeds will find out when to grow. But with beets and turnips you can sow some indoor, at the same time, and once they have couple of true leaves transplant them. Frost(even freez) is not a problem for them. But they will not germinate in the garden very soon, when it is cold.