How, when and why you need to mulch your Minnesota garden

Yes, this is a story about mulch.

Sounds like a real snoozer, I know. But mulching is one of the best things you can do for your garden. So grab some caffeine and follow along. Come spring, you'll thank me.

In a typical year, most perennials suited for Minnesota pop back no worse for the wear, even without mulch. Last year's polar vortex, however, proved there's no such thing as a typical year anymore. Deep, fluffy snow does make for great insulation for plants come winter, but extreme temperatures or a winter without snow could be fatal to your flowers, shrubs and trees. Mulch can go a long way in protecting your plants when nature turns nasty.

Mulch serves different purposes during the year. In summer, mulch helps to conserve moisture, suppress weeds, control erosion and give the garden a finished look. It can even stop the spread of disease by preventing water from splashing up onto foliage.

Once fall arrives, mulch performs yet another valuable job. Contrary to popular belief, it doesn't really keep plants cozy and warm, but it does moderate soil temperatures so that plants don't suffer from harmful fluctuations between warming and freezing in fall, spring or the "January thaw."

When temps dip into the single digits, mulch protects plants at the soil surface, where most roots are concentrated. It also helps stop frost heave. When this occurs, plants can be forced out of the ground, which exposes them to frigid temps and certain death. (This has happened to my heucheras when I'm not diligent about mulching them.)

Certain plants — such as recently planted bulbs, perennials, shrubs and trees — are more at risk for winter damage, so they welcome that added layer of protection. It's important to mulch strawberries, too, because while the plants themselves may be hardy, the flower buds that produce the fruit could use the extra covering.

Lately, lots of us in the metro area have been pushing the zones and trying plants that are not rated as hardy for USDA zone 4. These plants are particularly susceptible to winter damage and may need to be sheltered in deeper mulch, as well. For zone-pushing plants, use at least a 6-inch-thick layer of mulch. You also could consider making a cage out of fencing or hardware cloth and filling it with shredded leaves, or another organic mulch.

Straw makes a good winter mulch. It's lightweight and easy to spread and its hollow stems trap air, which adds to its insulating properties. It's also widely available now, when bales are sold for autumnal decor.

I prefer what's called lazy man's mulch: I just rake the leaves off my lawn and onto my perennial beds. More by-the-book gardeners run the lawn mower over the leaves first, because fluffy shredded leaves provide better insulation than matted ones.

If aesthetics aren't a concern, you can mulch beds with bagged leaves that can easily be removed come spring. Partly filled bags will make better contact with the ground.

It's best to wait until there's a hard frost to add winter mulch. But mulching a bit early is better than not mulching at all.

When mulching young or newly planted trees, make sure you pull the mulch a couple of inches away from the base of the plant. A thick layer of mulch up against the trunk creates an ideal environment for pests and diseases.

It's wise to leave winter mulch in place until the threat of frost is gone in spring.

Ah, spring. See, it's not all that far away, now is it?