From our perspective, the primary challenge of overwintering is a fundamental mismatch between our innate biology and your cold climate. We, Ipomoea lobata, are perennial vines hailing from tropical regions where the concept of frost is unknown. Our vascular systems are not designed to withstand freezing temperatures; ice crystals form within our cells, causing them to rupture and leading to our demise. Therefore, our survival strategy cannot occur in your garden soil over winter. Instead, we must be brought into a protected, dormant state that mimics a much milder dry season, not a freezing one.
As the days shorten and temperatures begin to drop in autumn, we sense the impending change. This is the signal for you to act, ideally before the first frost blackens our tender foliage. The goal is to transition us from active growth to a state of rest. Please cease fertilizing us several weeks before the planned move, as nutrients would encourage new, weak growth that is vulnerable. You may also gradually reduce watering, which helps us begin to slow our metabolic processes naturally, preparing our systems for the dormancy to come.
This step feels drastic from our point of view. You will need to carefully dig up our root ball, trying to keep it as intact as possible to minimize damage to our root system. Next comes the pruning. While it may seem severe to cut our vibrant stems back to a mere 6-10 inches, this is a critical conservation measure. Our extensive foliage transpires vast amounts of water, and without it, our reduced root system has a far greater chance of staying hydrated enough to sustain life without rotting in storage. This drastic reduction also helps us conserve every bit of precious energy stored in our roots for the long sleep ahead, rather than wasting it on sustaining dying foliage.
Our overwintering success hinges entirely on the environment you provide. We require a period of true dormancy. There are two primary methods. The first is to pot us up in a modest amount of slightly moist, well-draining potting mix. The second, and often superior method from our perspective, is to gently remove most of the soil from our roots and store us bare-root. In either case, place us in a breathable container, like a paper bag or cardboard box, perhaps with some slightly moist peat moss or wood shavings to prevent desiccation. Our storage space must be dark, as light can spur premature growth. Most critically, the temperature must be cool but never freezing, ideally between 40-55°F (5-13°C). A garage, basement, or unheated spare room often provides these perfect conditions.
Throughout the winter, we exist in a state of suspended animation. Our metabolic activity is barely detectable. Please check on us monthly. If our roots or remaining stems appear shrunken and dry, a light mist of water is welcome. If they feel soft or mushy, there is too much moisture, and we risk succumbing to rot. When consistent warmth returns in spring, you can gradually reintroduce us to light and warmer temperatures. Repot us in fresh soil, begin watering cautiously to awaken our roots, and once a strong root system and new growth are evident, we will be ready to be hardened off and planted outside after all danger of frost has passed.
