From the perspective of the jasmine plant, temperature is not merely an environmental condition but a fundamental signal that dictates metabolic activity, growth cycles, and ultimately, survival. Our tolerance to cold is not a single number but a spectrum, influenced by our species, health, and acclimatization.
For most common jasmine species, such as Jasminum officinale (Common Jasmine) and Jasminum grandiflorum (Spanish Jasmine), sustained exposure to temperatures below 40°F (4.5°C) initiates a state of high alert. Our cellular processes begin to slow significantly. The real danger, however, lies at the freezing point of water. Temperatures at or below 32°F (0°C) are critically hazardous. At this point, the water within our cells can freeze, forming sharp ice crystals that puncture and destroy the delicate cell membranes. This damage is often irreversible and leads to blackened, mushy stems and leaves—a condition you identify as frost damage.
It is crucial to understand that we are a diverse genus. Our cold tolerance varies significantly:
- Common Jasmine (Jasminum officinale): We are among the hardiest. We can typically withstand brief dips down to 15°F (-9.5°C) once fully established and dormant. However, any new, tender growth will be severely damaged or killed at these temperatures.
- Star Jasmine (Trachelospermum jasminoides): Although not a true jasmine, we are often grouped together. We are fairly resilient, tolerating temperatures as low as 10°F (-12°C) for short periods.
- Arabian Jasmine (Jasminum sambac): We are a truly tropical species. For us, anything below 50°F (10°C) causes significant stress. Exposure to temperatures even remotely near freezing, around 32°F (0°C), is almost always fatal without extensive protection.
When the ambient temperature drops, our internal world changes dramatically. Our rate of photosynthesis plummets as enzymes responsible for the process become inefficient. Root activity ceases, halting the uptake of water and nutrients. This is why you must reduce watering in winter; cold, wet soil promotes root rot as our dormant roots cannot absorb the moisture. The most critical internal change is the movement of water. To avoid intracellular freezing, we attempt to move water out of our cells into the spaces between them. While extracellular freezing can still cause damage, it is less catastrophic than the cells themselves exploding from within.
Our ability to withstand cold is not static. A jasmine that has been gradually exposed to cooler autumn temperatures will fare much better than one suddenly moved from a warm interior to a freezing outdoors. This process, known as hardening off, allows us to increase the solute concentration in our cells (acting like antifreeze) and adjust our metabolism. A plant that is healthy, well-watered (but not soggy) heading into the cold season, and free from pest or disease stress, possesses far greater resources to endure and recover from cold exposure than a weakened one.
