Putting your garden to bed with an organic mulch, such as straw, helps protect against frost heave in the garden. What is frost heave, you might ask? It’s the effect of having warm days then cold ones, making the ground an inhospitable one for plants. Perennial plants want to go to sleep for winter, and stay asleep, but frost-thaw cycles in the soil play havoc with that, waking them before it’s safe. In our city where continuous winter snow cover is rare, freeze-thaw is a pretty common occurrence.
The Iowa garden extension lists the perils of frost heave:
This repeated freezing and thawing causes the soil to expand and contract, which can lift up or heave some perennials out of the soil. Heaving may break off some of the plant’s roots. It also exposes the plant’s crown and remaining roots to cold temperatures and drying winds. Freezing and drying injury to a plant’s roots and crown may seriously damage or destroy perennials.
What is straw, anyway? And what’s the difference between straw and hay? Hay is the food source of the plant, the top half with the grain, that’s fed to animals. A Straw Bale builder explains the straw/hay difference here.
Straw, on the other hand, is simply the stalks of standing plants that contain no grain. The grain is harvested from the plants by a machine that cuts it off of the stalk. The grain is then removed from the field and the stalks are left to die, standing. Once they are totally dead and mostly devoid of moisture, they are cut, raked, and baled.
This means that straw has no seeds, making it a sterile mulch.
Benefits of Straw Mulch
- encourages earthworm activity
- regulates temperature of soil, keeps it cool, frozen, or warm
- when soil freezes, keeps it frozen
- stops soil from heaving
- organic mulch rots and improves soil
- keeps moisture in soil, bare soil loses moisture quickly.
- hollow straw stalks don’t compact or mat, the way leaves do
Tips for Using Straw Mulch
- keep away from stems of plants
- add layer of newspaper underneath, 5-7 sheets thick
- use on weeded soil
- apply once ground has had several hard frosts