Begonias are popular ornamental plants celebrated for their vibrant flowers and diverse, often strikingly patterned foliage. Successfully planting these tropical and subtropical natives directly into the ground depends entirely on the specific begonia type and your local climate conditions. Generally, begonias are tender perennials that cannot survive freezing temperatures, meaning ground planting is often a temporary seasonal display outside of the warmest regions. Understanding the plant’s root structure and your hardiness zone is the first step toward successful outdoor cultivation.
Which Begonias Can Be Planted Outdoors
Begonias are broadly categorized by their root systems, which determines their suitability for in-ground planting and overwintering. The most common varieties planted outdoors are fibrous-rooted and tuberous begonias.
Fibrous-rooted types, often called wax begonias, possess a shallow, dense root network. They are typically treated as annuals in most regions, providing continuous color until the first frost. Tuberous begonias grow from a fleshy, underground storage organ and are valued for their large, showy flowers. While they can be planted in the ground for the summer, they must be dug up and stored indoors before winter in areas that experience freezing temperatures.
Rhizomatous begonias grow from thick stems creeping along the soil surface. They are generally grown more for their elaborate foliage and are less commonly placed in garden beds, often performing better in containers or as houseplants. True perennial ground planting is only feasible in warmer climates, generally within USDA hardiness zones 9 through 11, where temperatures remain above freezing. A notable exception is Begonia grandis, sometimes called hardy begonia, which can tolerate winter conditions as far north as zone 6.
Optimal Site Selection and Ground Preparation
Selecting the correct location is important for the health and performance of begonias planted in the ground. Begonias thrive in areas that receive partial shade or filtered light, such as beneath a deciduous tree canopy. It is important to shelter them from the intense heat of the afternoon sun, which can easily scorch their delicate foliage.
Successful in-ground planting requires rich, well-draining soil to prevent root rot, a common issue. If your native garden soil is heavy clay or compacted, it must be heavily amended before planting. Incorporating generous amounts of organic matter, such as well-aged compost, finely ground bark, or composted manure, will improve both drainage and nutrient content.
The planting site should be prepared by loosening the soil to a depth of at least six to eight inches. Ensure the base of the plant is level with the surrounding soil to prevent water from pooling around the crown. Adequate drainage is more important than soil type, as begonias will not survive in waterlogged conditions.
Essential In-Ground Seasonal Care
Consistent moisture management is necessary for begonias planted in the ground throughout the active growing season. The soil should be kept evenly moist but never saturated; water only when the top one to two inches of soil feel dry to the touch. Watering at the base of the plant helps keep the foliage dry, which reduces the risk of fungal diseases like powdery mildew.
Ground-planted begonias benefit from regular nutrient delivery to support their continuous blooming habit. A balanced, water-soluble fertilizer can be applied every two to four weeks during the spring and summer months. Alternatively, a slow-release granular fertilizer can be incorporated into the soil at the time of planting for a steady supply of nutrients.
Routine maintenance includes removing spent flowers, a process known as deadheading, which redirects the plant’s energy into producing new blooms instead of seeds. Pinching back the tips of the stems encourages a bushier, more compact growth habit. Regularly inspecting the plants for yellowing leaves or signs of pests will help maintain their health.
Preparing Begonias for Cold Weather
The approach to winter preparation depends on the type of begonia planted and the local climate. Fibrous-rooted begonias are the least cold-tolerant. In regions with frost, they are typically treated as annuals and removed from the garden after the first hard frost kills the foliage. Their shallow roots are not designed to be easily salvaged or stored.
For tuberous begonias, which are popular for their large flowers, the tubers can be saved for the following year. After the foliage has been blackened by a light frost, cut the stems back to about an inch above the soil line. The tubers should then be carefully dug up, allowed to air-dry for several days to cure, and cleaned of excess soil and roots.
The cleaned tubers must be stored in a dark, dry, and cool location, where temperatures remain above freezing, ideally between 40 and 50 degrees Fahrenheit. Storing them in a container with materials like dry peat moss, sawdust, or vermiculite prevents moisture loss. This helps ensure they remain viable until they can be replanted the following spring.