Begonias are a widely popular group of ornamental plants, prized by gardeners for their vibrant flowers and diverse, often striking, foliage. These plants are frequently seen gracing flower beds, hanging baskets, and porch containers throughout the warmer months. The answer to whether they are permanent outdoor plants lies in the plant’s tropical heritage and the specific type of begonia being grown.
Understanding Begonias’ Tropical Origin
The genus Begonia is native to tropical and subtropical regions across the globe, including Central and South America, Africa, and Asia. This geographical origin is the most important factor determining their outdoor use outside of frost-free climates. As plants of the forest understory, they are naturally adapted to warm, consistent temperatures and high humidity.
Because of this tropical background, most begonias cannot tolerate cold temperatures. Temperatures consistently below 50°F (10°C) can damage or kill the plants, meaning they are not hardy in most of North America and Europe. They thrive only in USDA Hardiness Zones 9 to 11, where they can be grown as true perennials year-round. In temperate zones, begonias are treated as tender perennials or annuals, living outdoors only during the summer season after all danger of frost has passed.
Classifying Begonias for Outdoor Use
The success of growing begonias outdoors depends heavily on selecting the correct type, as they are broadly categorized by their root structure. The two types most commonly used for seasonal outdoor display are Wax Begonias and Tuberous Begonias.
Wax Begonias
Wax Begonias (Begonia semperflorens) are fibrous-rooted and are the classic bedding plant, often used as a reliable annual. They feature glossy, waxy leaves, which can be green or bronze, and produce small, continuous blooms throughout the season.
Tuberous Begonias
Tuberous Begonias (Begonia x tuberhybrida) are characterized by underground tubers, which are modified storage stems. These plants are known for their large, showy flowers, sometimes reaching four inches wide, in colors like yellow, orange, and red. They go through a natural dormancy period when temperatures cool.
Cane Begonias
Cane Begonias, such as the popular ‘Angel Wing’ varieties, are also fibrous-rooted but develop thick, bamboo-like stems. While many are grown as large houseplants, they are often moved outdoors for the summer months, particularly in containers, for their striking foliage and clusters of flowers.
Light, Soil, and Water Requirements Outdoors
Begonias generally perform best outdoors in conditions that mimic their native forest floor environment: bright light without intense, direct sun. Most varieties prefer partial shade or filtered light, as hot afternoon sun can easily scorch their foliage. An exception is the Wax Begonia, especially those with bronze foliage, which show a higher tolerance for full sun.
The planting medium must be rich in organic matter and have excellent drainage. Begonias are highly susceptible to root and stem rot if their roots sit in saturated soil. A slightly acidic, well-draining soil mix prevents waterlogging while still retaining enough moisture.
Watering should be consistent to maintain an evenly moist, but not soggy, environment. To prevent fungal diseases like powdery mildew, water should be directed at the base of the plant, avoiding the leaves and crown. Regular application of a balanced liquid fertilizer, typically once a month during the growing season, supports continuous flowering.
Seasonal Transition and Overwintering
Because begonias are not cold-hardy, managing the transition into and out of the outdoor season is necessary for long-term enjoyment. Before moving them outside in the spring, plants must be “hardened off” by gradually acclimating them to outdoor light and temperature over seven to ten days. They should not be placed outdoors until nighttime temperatures reliably remain above 50°F (10°C).
As autumn approaches and temperatures drop toward 45°F (7°C), different overwintering strategies are used based on the begonia type.
Tuberous Begonias
Tuberous Begonias are prepared for dormancy; the foliage is allowed to die back after the first light frost, and the tubers are then dug up. These tubers are cleaned, cured, and stored in a cool, dark, and dry location, packed in material like sawdust or peat moss.
Fibrous-Rooted Begonias
Fibrous-rooted types, such as Wax and Cane Begonias, do not have a natural dormancy and are instead brought indoors before the first frost to be treated as temporary houseplants. They should be placed in a location with bright, indirect light and monitored for pests. Reducing watering frequency ensures these plants survive the winter until they can be safely moved back outside the following spring.