From my perspective as a plant, the answer to your winter survival question begins with my origins. Most of my species, like the popular Passiflora incarnata (Maypop) and Passiflora caerulea, are native to warm, tropical, and subtropical regions of the Americas. This means my fundamental genetic programming is for warmth, sun, and long growing seasons. My vascular system is not inherently designed to withstand the deep, hard freeze that seizes water in my cells, causing them to expand and rupture—a fatal event for me. However, some of my kind, like the Maypop, have adapted to more temperate zones. We’ve developed extensive root systems that act as a survival mechanism, allowing the top growth to die back while the heart of the plant lives on underground, safely insulated from the frost above.
Your local USDA Plant Hardiness Zone is the most critical piece of information for us. It translates your climate's average extreme minimum winter temperature into a language I can understand. If you are in zones 9-11, many of my species can be evergreen or semi-evergreen perennials. My stems may experience some die-back in a rare cold snap, but my roots are generally safe in the ground. In zones 7 and 8, the story changes. Here, my above-ground vines will almost certainly die back to the ground after a hard frost. My survival depends entirely on my root system being well-mulched for protection. If you are in zone 6 or colder, the winter soil temperatures become a severe threat to my roots. Without significant and reliable insulation, the frozen ground can kill me entirely.
For those of us in cooler zones, our strategy is not to fight the winter but to sleep through it. As the days shorten and temperatures drop, I receive signals to slow my growth and begin drawing energy down into my roots. My leaves will yellow and drop, and my tender stems will turn brown and become brittle. This is not a sign of my death, but rather a deep dormancy. I am conserving every ounce of energy deep within my root ball, waiting silently beneath the soil. My entire existence is reduced to that buried store of nutrients, protected from the freezing air. I am in a state of suspended animation, and my survival hinges on the stability of this underground refuge.
Your actions as a gardener are vital to my success. Once the first frost has blackened my vines, please cut my stems back to about 6-12 inches above the soil line. This removes the dead material and helps prevent rot. Then, you must provide me with a thick, cozy blanket. Apply a deep layer of mulch—at least 4 to 6 inches—over my root zone. Use shredded bark, straw, pine needles, or a pile of fallen leaves. This layer does not heat the soil but acts as a magnificent insulator, preventing the rapid freeze-thaw cycles that can heave my roots from the ground and ensuring the soil temperature remains more stable. In pots, I am incredibly vulnerable, as my roots are exposed on all sides. I must be moved to a sheltered location like an unheated garage or shed where the temperature stays cool but does not freeze solid.
