Begonias, known for their diverse foliage and vibrant flowers, are popular for both indoor and outdoor cultivation. Maintaining appropriate environmental conditions is crucial for their robust growth and abundant blooms. Temperature is a primary factor influencing their overall health and development.
Ideal Temperature Range for Begonias
Most begonia varieties thrive within a consistent temperature range of 60°F to 75°F (15°C to 24°C) during the day. This range supports healthy development and vibrant flowering, mimicking their native subtropical and tropical warm, humid conditions. They generally benefit from a slight temperature drop at night, ideally settling between 55°F and 70°F (13°C and 21°C).
Indoors, maintain these conditions by setting a thermostat within the preferred range and keeping plants away from fluctuating temperatures near windows or vents. For outdoor begonias, especially in regions with distinct seasons, placement in naturally shaded spots is beneficial. Bring outdoor plants indoors before temperatures consistently fall below 55°F (13°C) to ensure their continued well-being.
Effects of Cold Temperatures
Begonias are sensitive to cold; exposure to temperatures outside their preferred range can lead to stress and damage. Symptoms include wilting leaves, black or brown spots, mushy stems, premature leaf drop, and stunted growth. Cold temperatures disrupt the plant’s cellular structure, particularly when freezing temperatures cause ice crystals to form and rupture cells.
Temperatures below 45°F (7°C) induce significant stress, increasing disease susceptibility. Freezing temperatures (32°F/0°C or below) are generally fatal to most begonia varieties, as cellular damage becomes irreversible. To protect begonias, bring potted plants indoors before the first frost or when nighttime temperatures consistently drop below 55°F (13°C). Outdoor plants can benefit from frost cloths for brief cold snaps, and avoiding cold drafts is important for indoor specimens.
Effects of Warm Temperatures
Excessively warm temperatures negatively impact begonias, causing heat stress. Symptoms include wilting or drooping leaves, scorching, and browning along the edges of foliage. Plants may exhibit reduced flowering or even enter a state of dormancy. Prolonged exposure to temperatures exceeding 85°F (29°C) can significantly stress begonias, leading to a decline in plant health. Temperatures above 109°F (43°C) can cause leaves to lighten in color and become more prone to sunburn.
To mitigate heat stress, providing adequate shade is important, such as placing outdoor plants where they receive morning sun and afternoon shade. Indoor begonias benefit from filtered light, which can be achieved with sheer curtains. Increasing humidity around the plants through methods like grouping them together, using pebble trays, or employing humidifiers can help, as begonias prefer relative humidity around 50-60%. Adjusting watering schedules to water deeply in the evening and checking soil moisture before watering also supports plants during warmer periods.
Adapting to Different Begonia Types
While a general temperature range suits most begonias, specific types exhibit slight variations in their preferences or tolerances. Tuberous begonias, for example, are sensitive to frost and often go dormant in winter. For active growth, they prefer warm temperatures, but for overwintering, their tubers should be stored in cool, dark, and dry conditions, ideally between 40°F and 50°F (4°C and 10°C).
Fibrous or wax begonias, commonly used as bedding plants, are more tolerant of heat and can even withstand some direct sun if gradually acclimated. They can also tolerate slightly cooler temperatures compared to tuberous varieties. Rhizomatous begonias encompass a diverse group, many of which appreciate stable indoor temperatures, generally above 60°F (15.5°C). Rex begonias, a type of rhizomatous, prefer a range of 60°F to 80°F (16°C to 27°C) and require high humidity.