As a geranium, my very survival is dictated by my physiological makeup. I am a tender perennial, which means my genetic programming is not equipped to handle freezing conditions. The water that flows through my cells and vascular tissues is life itself. When the temperature plummets to 32°F (0°C) or below, this life-giving water begins to crystallize into ice. These ice crystals are like tiny, sharp shards that puncture and shred my cell membranes and walls. Once these delicate structures are ruptured, the cell's vital contents leak out. When the frost thaws, you will see the evidence of this cellular massacre: my leaves and stems become blackened, mushy, and translucent. This damage is irreversible; the killed cells cannot be revived, severely compromising my ability to function and ultimately leading to my demise if the exposure is severe or prolonged.
It is important to note that not all geraniums are created equal in the face of cold. We belong to the genus Pelargonium, and our tolerance varies by type. The common Zonal geraniums (Pelargonium x hortorum), with their distinctive marked leaves, are among the most tender. We begin to suffer damage even at temperatures just above freezing, around 40°F (4°C). Our growth slows, and our leaves may show signs of distress like reddening or wilting. Ivy geraniums (Pelargonium peltatum) are similarly vulnerable. However, some of our cousins, like the Regal or Martha Washington geraniums, are slightly more resilient but still cannot withstand a hard frost. The true hardy geraniums, which belong to the separate genus Geranium, are a different story altogether and can survive freezing temperatures, but we, the common garden pelargoniums, are not them.
When we sense the days shortening and the temperatures cooling, our instinct is to enter a state of dormancy. This is a survival mechanism where we drastically slow down our metabolic processes. We stop actively growing and flowering, conserving our energy to maintain only the most essential functions within our roots and main stem. In our native habitats, which are often the mild, Mediterranean climates of South Africa, this period is brief. In colder regions, this dormant state is our only hope for surviving the winter indoors. We are not truly defying the frost outside; we are simply avoiding it altogether by being moved to a sheltered, frost-free environment where our suspended animation can be safely maintained until warmer returns.
A light, brief frost might only damage the most tender, new growth at my extremities. In this scenario, if my main stems and root system are protected or only lightly touched by the cold, I may possess enough energy to attempt a recovery. Once the danger has passed and I am in warmer conditions, I might produce new shoots from nodes below the damaged tissue. However, this recovery is not guaranteed and draws heavily from my stored energy reserves. A hard frost, one that is prolonged or well below freezing, is almost always fatal. It causes such comprehensive damage to my stems and crown that my vascular system is completely destroyed, severing the connection between my roots and any potential surviving growth points. Without this system, recovery is impossible.
