I know we shouldn't lay new mulch for winter protection until the ground freezes, how do I know when this is?
You are right. Do not apply mulch for winter protection until the ground freezes. This is generally after a week or so of freezing temperatures. The date varies from year to year and region to region. The purpose of winter mulch is to keep the ground frozen and avoid mid winter thaws that can result in early sprouting or frost heaving plants out of the ground.. Evergreen boughs, straw and marsh hay make great winter mulch. You can, however, apply soil mulches to the soil surface throughout the growing season.