Begonias are versatile plants prized for their vibrant flowers and attractive foliage, making them a popular choice for adding color to garden beds. While often grown in containers, successfully planting begonias directly into the ground requires specific preparation and care to ensure robust growth. This guide details the process of transitioning these tropical and subtropical plants to a permanent garden location, focusing on necessary environmental conditions and aftercare techniques.
Choosing the Ideal Site and Preparing the Soil
Selecting the correct location is the first step toward long-term success for in-ground begonias, as they are sensitive to harsh conditions. Most varieties thrive in an area that receives bright, filtered light throughout the day, such as beneath a tree canopy. Shield them from intense afternoon sun, which can easily scorch the foliage.
Proper soil structure is important because begonias are highly susceptible to root and stem rot when exposed to excessive moisture. The planting site must have excellent drainage, ensuring water never pools after rain or irrigation. Begonias prefer a slightly acidic soil composition, ideally with a pH range between 5.5 and 6.5.
Before planting, the native soil should be generously amended to create a fertile and well-aerated environment. Incorporating organic matter, such as compost, aged manure, or peat moss, improves the soil’s capacity to hold moisture while allowing excess water to drain quickly. For heavy, clay-based soils, adding gypsum or coarse sand helps break up the dense structure.
The Planting Process: From Pot to Ground
Planting must be timed carefully, as begonias are tender plants that cannot withstand frost. They should not be moved into the ground until all danger of the last spring frost has passed, and nighttime temperatures are consistently above 45°F. Starting plants indoors or purchasing established plants ensures a stronger root system before transplanting.
When preparing the site, dig a planting hole slightly wider than the root ball but no deeper. If planting a tuberous begonia, place the tuber shallowly in the soil, ensuring the concave side faces upward. For potted plants, gently loosen any tightly bound roots and set the plant so the top of the root ball is level with the surrounding soil.
Proper spacing is necessary to allow for air circulation and accommodate mature plant size, which ranges from 6 to 18 inches between plants depending on the variety. Backfill the hole with amended soil, gently firming it around the base to remove air pockets. This careful placement ensures the plant’s crown is not buried, preventing rot.
Essential Watering and Fertilization Aftercare
Immediately after planting, the begonia requires a deep watering to help the soil settle around the roots. This initial saturation is crucial for establishing good soil contact, but subsequent watering must prevent rot. Newly planted begonias need consistent moisture as they establish, often requiring watering every few days during dry conditions.
The key to a successful watering regimen is monitoring soil moisture, not adhering to a strict schedule. Established plants should only be watered when the top two to three inches of soil feel dry. Apply water directly to the base of the plant in the morning. This allows moisture on the leaves to dry before nightfall, reducing the risk of fungal diseases like powdery mildew.
Since begonias are heavy feeders, providing supplemental nutrients encourages robust growth and abundant flowering. Begin feeding with a balanced, slow-release granular fertilizer, such as a 20-20-20 formulation, applied once per month. For varieties grown primarily for blooms, a formula higher in phosphorus, like 15-30-15, stimulates flower production throughout the growing season.
Winterizing In-Ground Begonias
In most climates outside of USDA Hardiness Zones 9 and 10, in-ground begonias must be treated as annuals or the tubers must be lifted and stored for the winter. Fibrous-rooted begonias, often called wax begonias, are typically left in the ground to die back after the first hard frost. Tuberous begonias, however, can be preserved for another season.
The process of saving the tubers begins in the fall, just before the first expected hard frost. Reduce watering to encourage the foliage to yellow and the plant to enter dormancy, signaling the tuber is ready for storage. Carefully dig up the entire clump and cut the stems back to a few inches above the tuber.
The tubers must then be cured for several weeks in a dry, cool area to allow the skin to harden and heal over any wounds. After curing, gently brush off any remaining soil and remove all dried roots and stalks, as decaying organic matter can spread rot during storage. Store the clean, dry tubers in a dark, frost-free location, such as a basement or garage, at a temperature just above freezing, packed in a medium like dry peat moss or vermiculite.