Viewing post #1321770 by joannakat

Oldgardenrose said:Frost heaving is a real concept but it appears to only disturb new plants until they develop their root mass. I have used metal tent pegs or pieces of steel re-bar to hold landscaping timbers in place and had them raise out of the ground 3 or 4 inches after a few years. As an example of frost heaving, the soil freezes and expands with moisture which raises the shallow plant roots. When the soil thaws and settles back to normal the roots stay elevated. One of the old iris tricks is to place a half brick or stone on top of the new rhizome to force it to settle back down with the soil.

Most of the old-timers use mulch to keep the ground frozen, not to keep it warm. Applied after the ground freezes. Prevents the normal rapid thawing and freezing in the middle temp zones such as mine 6a/6b.

Great explanation. We get awful frost heaves in roads and sidewalks--bad enough to push up the paving! I've put flat stones around my fall plants (clematis and coral honeysuckle), but the instructions on my peonies called for 3" of mulch. It doesn't seem like much of a preventative to me though.