Timing Your Begonia Corm Planting
The principal factor dictating when to plant begonia corms revolves around the risk of frost. Begonias are tender plants, highly susceptible to cold temperatures. For the most reliable results, delay planting outdoors until all danger of frost has passed and the soil has begun to warm up sufficiently.
Generally, this means late spring, typically from April onwards in milder climates, extending into May or even early June in cooler regions of the United Kingdom. Planting too early risks exposing the developing corms or young plants to damaging cold snaps, which can stunt growth or even kill them. Conversely, waiting too long means a shorter flowering season.
Indoor starting offers a significant advantage, allowing you to get a head start on the growing season. Corms can be chitted (encouraged to sprout) indoors several weeks before the last frost date. This process involves placing the corms in a shallow tray filled with slightly damp peat or compost, in a warm, bright location. As the sprouts (often reddish or greenish shoots) begin to emerge, the corms are nearing readiness for planting out, or for potting on into larger containers if they will remain indoors for longer.
Observing the corms themselves is also a good indicator. Healthy corms will be firm and plump, often showing small buds or sprouts. If corms are shrivelled or soft, they may have been stored improperly and might not be viable. Ensure your corms are of good quality before you even consider planting times.
The challenge lies in balancing the plant's need for warmth with the desire for an early display. By understanding the specific climate of your region and the plant's sensitivity, you can pinpoint the opportune moment for planting begonia corms.
Understanding Corm Readiness and Viability
Before you even reach the planting stage, assessing the begonia corms themselves is vital. Healthy corms are the foundation of a successful display. They should feel firm and plump, not shrivelled or soft, which could indicate dehydration or rot from improper storage. Look for small, reddish or greenish buds or sprouts emerging from the concave side of the corm. These indicate the corm is beginning its active growth cycle and is primed for planting.
If you've purchased corms, they should ideally arrive in good condition. If storing them over winter, ensure they are kept in a cool, dry, and frost-free location, typically in a paper bag or peat. Regularly check stored corms for any signs of mould or excessive drying. Cots of rot should be discarded immediately to prevent it from spreading.
When planting, orient the corms correctly. The concave, indented side is where sprouts will emerge, so this should face upwards. The convex, rounded side is the base. Planting them upside down will hinder or prevent germination. A shallow planting depth is usually best, allowing the emerging shoots to reach the light without excessive effort. The quality of the corm directly influences the vigour of the plant and the timing of its bloom, making this initial assessment a critical step.
Alternative Planting Approaches and Considerations
While the primary consideration for when to plant begonia corms is frost avoidance, alternative methods and locations offer flexibility. Container gardening is an excellent option, particularly for patios, balconies, or gardens where soil conditions may be less than ideal. Pots and containers can be moved to warmer locations or brought indoors if unexpected cold strikes, offering a significant advantage in managing unpredictable spring weather.
The choice between planting corms directly into the ground or into pots depends on your garden's microclimate and your personal preferences. For beds and borders, planting directly allows for a more naturalistic display and can be more cost-effective for large numbers. However, containers allow for greater control over soil composition and drainage, which begonias appreciate. They also facilitate easier crop rotation and pest management.
For those interested in extending the begonia season, or living in very short-season climates, starting corms indoors and keeping them in containers for the entire season is a viable strategy. This ensures a continuous supply of blooms from early summer until the first autumn frosts. It also provides an opportunity to enjoy their vibrant colours on a patio or decking throughout the warmer months.
Consider also the type of begonia you are growing, as some varieties are more vigorous than others. Tuberous begonias, known for their spectacular large flowers, are the most common type grown from corms. Different cultivars may have slightly varying growth rates, but the fundamental requirement of warm soil and freedom from frost remains consistent across the board.
Preventing Common Planting Mistakes
A frequent error when planting begonia corms is rushing the process, driven by eagerness for summer blooms. This often results in planting too early, exposing vulnerable corms or seedlings to late frosts that can severely damage or kill them. Always consult reliable local weather forecasts and wait until the risk has genuinely passed.
Another common pitfall is improper corm preparation or orientation. Planting corms upside down, or failing to 'chit' them properly to encourage early sprouting, can lead to delayed or weak growth. Ensure the concave, budding side faces upwards. Furthermore, overcrowding corms can lead to competition for resources, resulting in stunted plants and fewer flowers. Adhering to recommended spacing ensures each plant has adequate room to thrive.
Overwatering is a silent killer of begonia corms, especially in the early stages. While they need moisture, corms sitting in waterlogged soil are highly prone to rot. Ensure your planting medium, whether in pots or the ground, offers excellent drainage. Allow the soil surface to dry slightly between waterings. This careful attention to drainage and watering regimes, alongside correct timing and preparation, is key to a bountiful begonia display.