I usually use around Thanksgiving as a rule of thumb ... usually the ground is frozen and the little furry creatures have secured somewhere else to winter ... like my house. I think this date was recommended by Winter Nursery but I could be wrong. I know I read it somewhere!
Linda

I don't really recomend mulch in your zone (3) or mine (5).

It can make the difference between life and death for plants not really hardy in your zone, but other than that it will kill more plants than it helps in the fall and spring if not removed due to the fact it insulates the cold ground to keep it cold longer and it retains moisture in what are usually excessively wet springs.

My personal opinion is that if you are mulching for winter warmth your best bet is a clear plastic sheet such as is used in warmer climates for solarization of the soil.

As long as their is no snowfall it will heat the soil, once there is snowfall it will insulate somewhat and in the early spring it is easy to remove so things don't stay wet. Leave it on in spring to get the soil warmed earlier.

In cold and/or wet climates mulch can be more of an enemy than a friend.

I find layers of pine boughs work very well for mulching. It keeps the soil frozen plus it keeps some are air near the plant crown.It gives you a little more time in the spring to get your mulch pulled back. Plus it makes your beds look nice all winter Works for me------------- Upnortdareh

Does anyone use grass clippings?
This year I had several bare dirt beds that are on a hill so I spread grass clippings to cover it for winter to keep soil from eroding. I'll till it in this spring.
Bad idea? Too much nitrogen?

Rich

Seems like I remember reading someplace that plastic for winter mulch isn't the best. I do like straw, especially since I can pull it back in the spring and use it on my paths. I'm careful about not taking the straw off too early, and covering it back at night if needed. So far so good, been doing that over 20 years here.

We have no shortage of mice and I don't want to make things too cozy for them, so will for sure wait till at least Thanksgiving to mulch.

Rich, the only thing I do with grass clippings is put them in the compost pile. But for a winter mulch, I don't see why they wouldn't work. There won't be much decomposing over the winter anyway.

Now I can see how winter wet could be devastating to certain plants, like some alpines. It is always a good thing to fluff winter mulch in the very early spring, long before you plan to remove it. I myself have some plastic over a small area where my Lilium nepalense is. It abhors winter moisture. But in general, at least for MN/WI, being colder with soil that freezes deeper and longer, and with drier springs than farther east, I can only see problems encouraging the soil to warm faster in springtime.

Plants wake earlier, making tender growth more vulnerable to late frosts. That is a major reason for mulching - to prevent premature growth that is prone to frost. Now on the other hand, plastic for a warm season vegetable garden would be a good thing for the same reason.

Regarding grass clipping, I see no reason why they can't be used for winter mulch, but even though it is through the winter, my guess is that there won't be much left by spring. A worthy experiment. See what happens.

Rick

I'd stay away from grass clippings as they mat down and mold over winter and can literally suffocate the plants and rot the crowns. They will not break down much once temps stay below 50. The primary reason to mulch is to prevent heaving, insolation is secondary (unless its for roses). I agree with upnortdareh. Any kind of conifer boughs will keep the soil shaded to avoid thaws yet allow for air and water circulation. Larger, dried, curly leaves (i.e. maple leaves) under the boughs will add isolation, if needed but stay clear of flat or shredded leaves as these too will tend to mat. As for plastic, that could be a real problem with baking the plants on a warm, sunny day.

T.J.

Some of this discussion is site specific (there are mulches I can get away with in my well drained garden that I wouldn't attempt when I gardened on clay) & it also presupposes that the crowns of the plants are not covered. Except for maybe boughs, most any mulch will smother if applied directly on top of the plant. Applied between the plants, I don't think any of the organic mulches discussed here would cause harm.

One thing about mulching in the fall in Wisconsin is that even if you use rotten hay,grass clippings,leaves etc.you may attract some rodents such as mice to your garden in the fall but by May if you lift your mulch and turn with a fork over it any rodents will leave and besides if the little fury guys winter in your mulch at least they wont be coming inside your home.

Since posting this, I researched and found some good information (our temperatures around Thanksgiving this year were almost balmy):
Timing is critical when applying winter mulch. Applying it too early can smother the plant and encourage disease development. Once the plants are completely dormant and temperatures are consistently below freezing, then the winter mulch can be applied. In most cases, 2 to 4 inches of organic material such as straw, pine needles, hay, or bark chips, will provide adequate protection.