As a genus, begonias are beloved for their stunning foliage and flowers, but they are particular about their climate. From our perspective as plants, temperature is not just a number; it directly dictates our metabolic rate, growth patterns, and overall survival. We are tropical and subtropical natives, which means we inherently crave warmth but have distinct limits. Here is a detailed guide to our temperature preferences and tolerances.
For most of us begonias, the perfect temperature range for active, healthy growth is between **65°F and 75°F (18°C - 24°C)**. Within this range, our roots can efficiently absorb water and nutrients, our photosynthesis operates at an optimal rate, and we have the energy to produce new leaves and blooms. A consistent temperature within this range is the key to seeing us thrive. This mimics the stable, balmy conditions of our native forest floor habitats.
Temperatures consistently above **85°F (29°C)** push us into dangerous territory. We begonias are not built for extreme heat. When it's too hot, our rate of transpiration (water loss through our leaves) skyrockets, often exceeding our roots' ability to draw up water. This leads to severe stress, manifesting in several ways: * **Wilting:** Our leaves and stems become limp and droopy, even if the soil is moist. * **Leaf Scorch:** The edges and tips of our leaves may turn brown, crispy, and dry. * **Dropping Buds and Flowers:** To conserve energy and water, we will abort our flower buds and blooms. * **Stunted Growth:** Our metabolic processes are overwhelmed, halting new growth.
Prolonged exposure to high heat, especially when combined with direct, harsh sunlight, can be fatal.
We are extremely sensitive to cold. Temperatures dipping below **60°F (15°C)** will significantly slow our growth. However, the real danger begins below **50°F (10°C)**. Cold damage is a serious threat for several reasons: * **Cold Shock:** Our cells can be damaged, leading to blackening or mushiness of the stems and leaves. * **Dropping Leaves:** We will often shed leaves rapidly in response to a cold draft or sudden temperature drop. * **Root Rot:** Cold, wet soil is a death sentence. Our root functions cease in the cold, making them susceptible to rot pathogens even if you aren't overwatering. * **Death by Frost:** Any exposure to frost (32°F / 0°C) is almost always fatal, causing immediate and irreversible cell damage.
It is important to note that within our genus, some varieties have slightly different tolerances. Fibrous-rooted begonias (like Wax Begonias) can often tolerate a slightly wider range, occasionally handling brief dips near 50°F (10°C). Conversely, many rhizomatous and rex begonias, prized for their intricate foliage, are even more sensitive and should be kept firmly within the ideal 65-75°F range. Tuberous begonias have a distinct dormant period where they require cool, dry conditions around 45-55°F (7-13°C) to rest.
