What Are Begonia Corms and Why Plant Them?
Planting begonia corms offers a straightforward path to cultivating these spectacular plants, known for their lush foliage and eye-catching flowers. Unlike seeds or cuttings, corms are dormant, specialised underground stems that store nutrients, making them resilient and reliable for propagation. They provide a head start compared to starting from seed, often leading to earlier and more vigorous flowering.
- Corms store energy, promoting strong initial growth.
- They offer a reliable method for propagation.
- Successful planting leads to vibrant blooms and foliage.
- Corms provide a head start over seeds.
- They are a cost-effective way to grow multiple plants.
The appeal of planting begonia corms lies in their potential for prolific blooming and diverse forms. From the cascading 'waterfall' varieties perfect for hanging baskets to the upright, dinner-plate sized blooms of the Tuberous types, there’s a begonia to suit almost any aesthetic. They can transform patios, balconies, and garden beds into vibrant displays, offering a continuous show of colour from summer until the first frosts. Choosing to plant corms is often more economical than buying established plants, allowing gardeners to cultivate a larger collection or experiment with different varieties.
Begonias vs. Other Flowering Plants
When considering summer bedding or container plants, begonias, grown from corms, present a compelling option against alternatives like petunias, marigolds, or geraniums. While other plants might offer different strengths – petunias for trailing abundance, marigolds for pest deterrence, or geraniums for reliable bedding – begonias excel in shade tolerance and unique flower forms. Many varieties thrive in dappled shade where other sun-lovers struggle, making them ideal for difficult garden spots. Their textured leaves and complex, often ruffled, flowers add a sophisticated dimension that can elevate a planting scheme.
Prepare your corms by placing them in a shallow tray with slightly damp peat or compost a few weeks before planting outdoors, concave side up, in a bright, frost-free spot. This encourages them to sprout, giving them a vital boost.
Beyond their aesthetic qualities, planting begonia corms is a foundational step for gardeners seeking to understand plant propagation through vegetative means. It demystifies the process of growing from a non-seed source, building confidence for tackling other tubers or bulbs later on. The anticipation of seeing those first shoots emerge from the soil is a unique pleasure, connecting the gardener directly to the plant's life cycle.
When and How to Start Planting Begonia Corms
The timing for planting begonia corms is crucial for their successful establishment and subsequent flowering. These plants are tender and susceptible to frost, meaning they should only be planted outdoors once all danger of frost has passed in your region. Typically, this aligns with late spring or early summer, depending on your local climate. Starting them indoors a few weeks earlier, however, can give you a significant head start.
Indoor Sowing and Early Care
To get ahead, begin planting begonia corms indoors approximately 6-8 weeks before the last expected frost. Use shallow trays filled with a good quality, free-draining seed compost or a mix of peat and perlite. Place the corms, concave (hollow) side facing upwards, on the surface of the compost. The concave side is where the new shoots will emerge, so orienting them correctly is important. Gently press them into the compost so they are just covered, or leave them resting on top if they are already showing signs of sprouting.
Keep the trays in a warm, bright location, ideally around 18-21°C (65-70°F). Avoid direct, harsh sunlight at this stage, as it can scorch the emerging shoots. Maintain consistent moisture; the compost should be damp but not waterlogged. Overwatering is a common pitfall that can lead to corm rot. If you are unsure, misting the surface regularly is often sufficient until shoots appear.
As the corms begin to sprout, you will see small, reddish shoots emerging from the concave side. Once these shoots are about 1-2 cm (around half an inch) tall, you can carefully pot them into individual small pots, using a standard potting compost. Continue to grow them on in a bright spot, watering sparingly, and gradually acclimatise them to cooler conditions before the final outdoor planting.
Outdoor Planting Considerations
When planting begonia corms directly into the ground or into containers for outdoor display, ensure the soil is warm and has fully dried out from any lingering winter moisture. Choose a location that offers partial shade; while some varieties can tolerate more sun, most begonias perform best with protection from intense midday heat, which can scorch their leaves and flowers. The soil should be fertile and free-draining. If planting in beds, incorporate plenty of organic matter like compost or well-rotted manure to improve soil structure and fertility.
For container planting, a high-quality potting mix is ideal. When planting multiple corms in a container, space them according to the plant's mature size, typically 15-30 cm (6-12 inches) apart, depending on the variety. Bury the corms about 2-3 cm (1 inch) deep, with the concave side facing upwards. Water them in gently after planting. If planting into the garden, dig a hole large enough to accommodate the corm and a little extra space for root development.
The success of planting begonia corms hinges on providing the right conditions for germination and growth, balancing warmth, light, and moisture without overdoing it.
Check the weather forecast diligently before moving plants outdoors. A sudden late frost can set back your efforts considerably, so be prepared to cover tender plants or move containers under cover if cold snaps are predicted.
Some gardeners opt to plant begonia corms in slightly raised beds or containers to ensure superior drainage, a vital factor in preventing rot. This is particularly relevant in areas with heavy clay soil or high rainfall. The depth of planting is also key; too deep and the corm may struggle to sprout, too shallow and it risks drying out or being damaged by surface conditions.
Alternatives and Companion Planting
While planting begonia corms is a fantastic choice for many garden situations, exploring alternatives and companion planting can enrich your garden's biodiversity and aesthetic appeal. The term 'begonia' itself covers a vast range of plants, and understanding the specific type of begonia corm you are planting can inform your choices for companion plants and alternative strategies.
Exploring Different Begonia Varieties
Begonia corms primarily come from tuberous-rooted or rhizomatous varieties, each offering distinct growth habits and flower types. Tuberous begonias are renowned for their large, often flamboyant flowers, making them excellent for containers and hanging baskets. Their corms are typically larger and more irregular in shape than those of other plants. Rhizomatous begonias, while sometimes grown for their foliage, also produce flowers, though their propagation might lean more towards division of the rhizome itself rather than distinct corms in the same way.
If you find begonia corms challenging to source or prefer a different aesthetic, consider other summer-flowering bulbs or tubers. Dahlias offer an incredible array of colours and forms, from small pom-poms to dinner-plate sized blooms, though they generally require more sun. Gloxinias (Sinningia speciosa) are closely related and are planted from tubers that look very similar to begonia corms; they also prefer warmth and humidity and are excellent for indoor displays or sheltered garden spots. Other options like tuberous-rooted lilies or even ornamental sweet peas grown from seed can provide different textures and colours.
Companion Planting for Begonias
When planting begonia corms, consider companion plants that complement their needs and aesthetic. Begonias often thrive in partial shade and moist, well-drained soil, conditions that are also favourable for many ferns, hostas, and impatiens. Planting them alongside these can create a lush, shade-tolerant display.
For containers, trailing begonias can be paired with upright or mounding plants. Consider combining them with trailing lobelia for a soft blue contrast, or with compact fuchsias, which also appreciate similar growing conditions and can offer a complementary bloom shape. Smaller foliage plants like heucheras (coral bells) with their colourful leaves can provide a striking backdrop or contrast to the begonia's flowers. Nasturtiums, while preferring more sun, can sometimes tolerate partial shade and add a cheerful splash of orange or yellow, though their vigorous growth might need managing.
Avoid planting begonias with species that require very different conditions, such as drought-tolerant succulents or sun-loving annuals like marigolds in their full-sun locations. Ensure that companion plants do not compete aggressively for water or nutrients, especially in containers. The goal is to create a harmonious planting where each plant can flourish without hindering the others.
Observe the light conditions in your garden throughout the day. What appears to be full sun might actually be partial shade for much of the afternoon, a spot where begonias can excel, unlike many other summer blooms.
When planning your planting, think about the mature size of all the plants involved. Overcrowding is detrimental to all plants, but particularly to those grown from corms, which need space for root development and air circulation to prevent disease. A well-planned planting scheme, whether using begonia corms or other options, maximises visual impact and plant health.
Troubleshooting and Care After Planting
Once your begonia corms are planted, consistent care is key to ensuring they develop into healthy, floriferous plants. Understanding potential issues and how to address them will help you achieve the best results from your planting efforts.
Common Problems and Solutions
One of the most frequent problems encountered when planting begonia corms is rot. This is usually caused by overwatering or poor drainage, especially in cooler soil temperatures. If you notice your corm is mushy, discoloured, or fails to sprout, it has likely rotted. The best preventative measure is to ensure excellent drainage, both in pots and in garden beds, and to water only when the top inch of soil feels dry. If planting indoors, use a well-draining compost mix and avoid waterlogging the trays.
Another issue can be leggy or weak growth, which often occurs when plants are kept in insufficient light after sprouting. While begonias prefer protection from harsh midday sun, they still need bright, indirect light to grow strong stems. If your indoor-started corms are stretching towards the light, move them to a brighter location. For outdoor plants, ensure they are not shaded too heavily by larger shrubs or trees.
Pests like aphids or spider mites can occasionally affect begonias, particularly if the plants are stressed. Regular inspection of the leaves and stems can help catch infestations early. Often, a strong jet of water can dislodge aphids, or a mild insecticidal soap can be used for more persistent problems. Good air circulation around the plants also helps deter pests and diseases.
Ongoing Care for Blooming Begonias
As your begonia plants grow, continue to provide consistent watering. During hot, dry spells, they may need watering daily, especially if grown in containers which dry out more quickly. When watering, aim to wet the soil directly rather than the foliage, as wet leaves can encourage fungal diseases.
Feeding your begonias will encourage more abundant flowering. Start feeding with a balanced liquid fertiliser once the plants are established and showing active growth. As they begin to bloom, switch to a fertiliser that is higher in potassium, which promotes flower development. Follow the fertiliser manufacturer's instructions carefully, as over-fertilising can damage the roots. Many gardeners feed every 2-4 weeks during the growing season.
Deadheading spent flowers is also beneficial. Removing blooms as they fade encourages the plant to put its energy into producing more flowers rather than developing seeds. Simply pinch or snip off the faded flower stalks at their base. This keeps the plant looking tidy and promotes continuous blooming.
Protect your begonia plants from strong winds, which can damage their delicate stems and flowers. Planting them in a sheltered spot or providing staking for taller varieties can prevent physical damage.
As autumn approaches and temperatures begin to drop, the plants will naturally start to slow their growth. In frost-prone areas, begonia plants are not hardy and will need to be protected or lifted. Before the first hard frost, you can dig up the corms, gently clean off any excess soil, and allow them to dry thoroughly in a cool, airy place for a few weeks. Store them over winter in a dry, frost-free location, perhaps in trays of peat or dry sand, ready for planting again the following spring.