The genus Begonia is one of the largest groups of flowering plants, containing over 2,000 species and countless hybrids native to tropical and subtropical regions globally. This immense diversity means that the question “how fast do begonias grow” does not have a single answer. A begonia’s growth rate is a direct reflection of its genetic makeup, or type, which dictates its natural size, growth habit, and whether it enters a period of dormancy. Understanding these inherent differences helps predict and influence how quickly any individual plant will develop.
Categorizing Growth Speed by Begonia Type
Growth rates among begonias are primarily determined by their root structure and stem type, leading to three main categories with distinct growth habits. Cane-like begonias, such as ‘Angel Wing’ varieties, are generally the fastest and tallest growers. Their stems have jointed, bamboo-like sections, allowing them to reach heights of up to six feet or more under ideal conditions. Vigorous hybrids, such as the ‘Dragon Wing’ or ‘BIG’ series, often reach three feet in a single season.
Fibrous-rooted begonias, which include the common wax begonias (Begonia semperflorens), exhibit a rapid but compact growth pattern. These plants quickly reach their mature, bushy size of 6 to 12 inches and are often grown as annual bedding plants due to their continuous flowering. In contrast, rhizomatous begonias, such as Rex varieties, focus their growth energy horizontally. They spread via thick, creeping stems (rhizomes) near the soil surface, resulting in a mounding habit and a slower vertical growth rate, making them prized for their spectacular foliage.
Tuberous begonias have a highly seasonal growth cycle defined by their fleshy underground storage tuber. They exhibit rapid, concentrated growth when they emerge in spring and summer, quickly pushing out large flowers and foliage. This fast development is followed by a natural decline, as the plant reserves energy back into the tuber for winter dormancy, halting all visible growth until the next season.
Environmental Factors Influencing Growth Rate
Even with a plant’s inherent growth potential, external environmental conditions must be optimal. Begonias thrive in bright, indirect light, mimicking their native habitat as understory plants in tropical forests. Too little light slows photosynthesis, resulting in stunted growth and pale, leggy stems. Conversely, too much direct afternoon sunlight, especially in warm climates, can scorch the leaves and stunt the plant’s development.
Temperature and humidity play a significant role in maintaining a steady growth rate. Begonias prefer consistent temperatures, ideally between 65°F and 75°F, and will suffer growth setbacks or cold damage if temperatures drop below 45°F. As tropical plants, they require moderate to high humidity, typically 40% to 60%. Some foliage types, like Rex begonias, need levels above 75% to prevent leaf edges from curling and growth from slowing.
Consistent water management is necessary for uninterrupted growth, since begonias need moist, well-draining soil without becoming waterlogged. The soil should be allowed to dry slightly, about an inch or two deep, between waterings to prevent root rot, a major cause of sudden growth cessation and plant death. A lack of consistent moisture will also put the plant under stress, causing it to slow or halt expansion until proper hydration is restored.
Managing Growth for Desired Speed and Size
Active intervention through feeding and physical manipulation allows a grower to fine-tune a begonia’s growth speed and shape. Since begonias are heavy feeders, providing a balanced, water-soluble fertilizer every two to four weeks during the active growing season fuels rapid development. For varieties grown specifically for their flowers, such as tuberous types, switching to a high-phosphorus formulation (e.g., 15-30-15 ratio) encourages bloom production over vegetative growth.
Pruning and pinching are targeted actions used to redirect the plant’s energy and manage its size and habit. Pinching off the soft growing tips of stems, particularly on young cane-like begonias, forces the plant to branch out laterally, creating a bushier, more compact specimen. This technique slows vertical ascent but increases overall plant volume, providing a denser appearance. Deadheading, the removal of spent flowers, conserves the plant’s energy by preventing it from setting seed, allowing it to produce new foliage and more blooms.
Managing the dormancy of tuberous varieties is the most direct way to control their yearly growth cycle. As the plant slows down in late summer, reducing watering and stopping fertilization signals the plant to prepare for rest. The tubers are then dug up and stored in a cool, dry place over winter, pausing growth until they are replanted the following spring for a fresh burst of rapid, seasonal development.