Table of Contents
- Introduction
- Understanding Your Begonia Corms
- Timing Your Planting for Success
- Selecting the Perfect Location
- Preparing Your Soil and Containers
- How to Plant Begonia Corms: Step-by-Step
- Caring for Begonias After Planting
- Special Considerations for Containers and Hanging Baskets
- Overwintering Basics
- Conclusion
- FAQ
Introduction
Shade gardens often feel like quiet retreats, but they can be just as vibrant as the sunniest flower bed. Tuberous begonias are the superstars of these cooler spaces. They offer lush foliage and spectacular, rose-like blooms that last from midsummer right through the first frost. At Longfield Gardens, we love how these plants transform hanging baskets, patio pots, and garden borders with their brilliant colors and varied textures.
Learning how to plant begonia corms is a rewarding skill for any gardener. These plants are easy to grow once you understand their unique needs and growth cycle. Whether you are looking for upright varieties to fill a garden bed or cascading types for a porch display, the process starts with a few simple steps. This guide will walk you through everything from timing and soil preparation to the specific technique of tucking corms into the ground.
By the end of this article, you will know exactly how to give your begonias the best start possible. We will cover the specific orientation of the corms, the best light conditions for growth, and how to transition your plants from indoors to the garden.
Understanding Your Begonia Corms
Before you get your hands in the dirt, it helps to understand what a begonia corm actually is. While many people call them "bulbs," they are technically tubers or corms. These are thickened, underground stems that store energy for the plant. Because begonias are tropical plants, these corms are sensitive to cold but very efficient at producing flowers once the weather warms up.
When you receive your corms from us, you might notice they look a bit like small, brown, shaggy pucks. They are often bowl-shaped, with one side that is rounded and another side that has a noticeable indentation or "hollow." This shape is the most important thing to notice. The hollow, concave side is the top, where the stems and leaves will emerge. The rounded, smoother side is the bottom, where the roots will grow.
Healthy corms should feel firm to the touch. If you see a little bit of surface mold, do not worry. This is common during shipping and can be gently brushed off. The most important factor is the internal health of the corm, which should feel solid rather than soft or mushy. For delivery timing, see our Shipping Information.
Why Quality Matters
Starting with high-quality corms makes the entire planting process easier. Larger corms typically have more stored energy, which leads to more stems and a greater abundance of flowers. At Longfield Gardens, we provide premium corms that are true to variety, ensuring that the colors and shapes you choose are exactly what you see in your garden.
Timing Your Planting for Success
Timing is the most important factor when planting begonias. Because these are tropical plants, they have no tolerance for frost. If they are planted in cold, wet soil too early, the corms can rot before they ever have a chance to sprout.
Starting Indoors (The Head Start)
Most gardeners in the United States choose to start their begonia corms indoors, and When Can You Plant Begonias? explains the timing in more detail. Begonias are slow starters and can take six to eight weeks to produce their first sprouts. By starting them inside in late winter or early spring (usually March or April), you ensure they are well-established and ready to bloom by the time summer arrives.
If you wait until the soil is warm enough to plant them directly outside, you might not see flowers until very late in the season. Starting them in a warm, indoor environment gives you an extra two months of growth. This results in fuller plants and a much longer flowering window.
Transitioning Outdoors
You should only move your begonias outside once the danger of frost has completely passed. More importantly, wait until the overnight temperatures consistently stay above 60°F. To check your growing zone, use the Hardiness Zone Map.
Key Takeaway: The Timing Rule
- Start corms indoors 8–12 weeks before the last frost.
- Move plants outside only when night temperatures are above 60°F.
- Patience in the spring leads to more flowers in the summer.
Selecting the Perfect Location
Begonias are famous for their love of shade, but "shade" can mean different things. Finding the right balance of light and protection will help your plants reach their full potential.
Light Requirements
Tuberous begonias prefer partial shade or filtered sunlight. For more light guidance, see Are Begonias Shade or Sun Plants?. In many regions, the morning sun is fine, but the intense, direct heat of the afternoon sun can scorch their leaves and cause the flowers to wilt. If you live in a very hot climate, your begonias will appreciate even more shade.
Underneath a large tree, on a north-facing porch, or along a shaded walkway are all excellent locations. The goal is to provide enough light so the stems don't become "leggy" (stretched out and weak) but not so much that the plant feels stressed by heat.
Wind and Shelter
Begonias have thick, succulent stems that are full of water. While this makes them sturdy, it also makes them somewhat brittle. A strong gust of wind can snap a heavy, bloom-laden stem. When choosing a spot, look for an area that is somewhat sheltered from high winds. This is especially important for trailing or cascading varieties in hanging baskets, which can act like sails in a storm.
Soil and Drainage
The word "drainage" simply means how fast water leaves the soil. Begonias need consistent moisture, but they hate sitting in "wet feet." If the soil stays soggy for too long, the corm can rot.
Whether you are planting in the ground or a container, use soil that is light and porous. If your garden soil is heavy clay, it is often better to grow begonias in raised beds or pots where you can control the drainage more easily. For landscape planting tips, see Can Begonias Be Planted in the Ground?.
Preparing Your Soil and Containers
Whether you are starting your corms in a tray indoors or planting them in their final summer home, preparation is key.
Choosing a Container
If you are starting corms indoors, you can use shallow trays or individual small pots. Ensure every container has drainage holes at the bottom. For the final summer display, choose a pot that is at least 6–8 inches deep to allow room for the root system to expand.
The Right Potting Mix
For containers, a high-quality, peat-based potting soil is usually best. These mixes are designed to hold onto the moisture begonias love while letting excess water drain away freely. Avoid using "garden soil" or "topsoil" in pots, as these are too heavy and will compact over time, cutting off oxygen to the roots.
If you are planting in a garden bed, you can improve the soil by mixing in some compost or well-rotted leaf mold. This adds nutrients and improves the soil structure, making it easier for the begonia's fine roots to spread.
How to Plant Begonia Corms: Step-by-Step
Once you have your corms and your site ready, the actual planting process is quite simple. Follow these steps for both indoor starting and outdoor planting.
Step 1: Identify the Top
Look at the corm and find the side with the indentation. This bowl-shaped hollow should always face up. You may see small, pinkish buds or "eyes" starting to form in the hollow; these are the future stems. The smooth, rounded side goes down into the soil.
Step 2: Set the Depth
Begonias do not like to be buried deep. In fact, planting them too deep is a common reason why they might fail to sprout.
- Indoors: Gently press the corm into the soil so the top is just level with the surface. You can leave the very center of the hollow exposed.
- Outdoors: Cover the corm with no more than 1/2 inch to 1 inch of soil.
Step 3: Spacing
Give your begonias room to breathe. Proper spacing ensures good airflow, which helps prevent mildew and other leaf issues. For a deeper look at spacing, read How Far Apart Do You Plant Begonias?.
- In containers: Plant corms 6–10 inches apart. A standard 12-inch hanging basket can usually hold two or three corms.
- In the garden: Space corms 10–12 inches apart to allow the foliage to fill in without crowding.
Step 4: Initial Watering
After planting, water the soil lightly to settle it around the corm. Do not soak it. While the corm is dormant (not yet growing), it doesn't have roots to take up water. Excessively wet soil at this stage can lead to rot.
What to Do Next
- Identify the hollow side of the corm.
- Press the corm into the soil with the hollow facing the sky.
- Cover with only a thin layer of soil (1/2 inch).
- Water lightly and place in a warm spot (at least 60°F).
Caring for Begonias After Planting
Once your corms are in the ground or the pot, the focus shifts to maintaining a steady environment for growth.
Monitoring for Sprouts
Be patient. It can take several weeks for the first green shoots to appear. During this time, keep the soil "barely moist"—similar to the feel of a wrung-out sponge. If you are starting them indoors, placing the pots on a warm surface or in a sunny window (but out of direct, hot sun) can help speed up the process.
Managing Moisture
As the leaves begin to grow and the weather warms up, the plant will need more water. The goal is to keep the soil consistently damp but never waterlogged. A good rule of thumb is to check the soil with your finger. If the top inch feels dry, it is time to water. For a broader care refresher, see How to Take Care of a Begonia Plant.
Try to water at the base of the plant rather than over the leaves. Wet foliage in a shaded area can sometimes lead to powdery mildew. Watering in the morning is also helpful, as it allows any accidental splashes on the leaves to dry during the day.
Feeding Your Plants
Begonias are heavy feeders because they produce so many large flowers over a long period. Once the plants are about 4–6 inches tall and have several sets of leaves, you can begin a regular fertilizing routine.
A balanced, water-soluble fertilizer applied every two weeks is usually sufficient. Some gardeners prefer a fertilizer with a slightly higher middle number (phosphorus) to encourage more blooms. Always follow the instructions on the fertilizer label to avoid over-feeding, which can burn the roots.
Maintenance and Deadheading
Begonias are relatively low-maintenance, but a little grooming goes a long way. "Deadheading" is the process of removing faded or spent flowers. By snapping off the old blooms, you prevent the plant from putting energy into seed production and encourage it to keep producing new flowers.
You should also remove any yellowed or damaged leaves throughout the season. This keeps the plant looking tidy and improves airflow around the stems.
Special Considerations for Containers and Hanging Baskets
Begonias are arguably the best choice for shade-loving containers. Browse our hanging begonias collection for trailing types. However, plants in pots have different needs than those in the ground.
Watering in Pots
Containers dry out much faster than garden beds. In the heat of midsummer, a hanging basket may need water every day. If you want a standout trailing variety, Begonia Hanging Golden Balcony is a strong choice for shady porches and decks.
Weight Management
Because begonia corms and their stems are full of water, they can become quite heavy. If you want another full, colorful option, Begonia Non Stop Mix - Bulk Offer is a good fit for baskets.
Trailing Varieties
If you are planting cascading begonias (often labeled as Begonia pendula), they will naturally begin to arch over the sides of the pot as they grow. When planting these, you can tilt the corm slightly toward the edge of the pot to encourage that beautiful "waterfall" effect of flowers. Begonia Hanging Pink Balcony is a classic example.
Overwintering Basics
In most of the United States, begonias will not survive the winter outdoors. If you want to enjoy your flowers again next year, you will need to "overwinter" the corm.
Once the first light frost hits and the foliage begins to turn yellow or black, it is time to bring them in. Cut the stems back to about an inch above the corm. Carefully dig up the corm, being careful not to nick it with your shovel.
Let the corms dry in a cool, indoor spot for a few days until the remaining bit of stem falls off naturally. Once dry, you can store them in a paper bag or a box filled with dry peat moss or sawdust. Keep them in a cool (40–50°F), dark, dry place like a basement or closet until next spring.
Conclusion
Planting begonia corms is a simple way to bring professional-level beauty to the shaded corners of your home and garden. By starting them indoors, paying attention to the orientation of the corm, and providing consistent moisture, you can enjoy a spectacular display of color all summer long.
At Longfield Gardens, we want your gardening experience to be as rewarding as possible. Remember that gardening is a journey, and every season brings new opportunities to learn and grow. Whether you are planting a single pot for your porch or a long border in your backyard, the results are well worth the effort.
Final Checklist for Success
- Confirm the hollow side faces up.
- Keep the planting depth shallow (1/2 inch).
- Wait for warm nights (60°F+) before moving plants outside.
- Provide partial shade and steady moisture.
We look forward to helping you grow a more beautiful garden this year. For more tips and to see our current selection of varieties, feel free to explore our planning guides and articles.
FAQ
Which side of the begonia corm should face up?
The side with the indentation or "hollow" should always face upward when planting. This is where the stems and leaves will emerge, while the rounded, smoother side is the bottom where roots will grow. If you cannot tell which side is which, you can plant the corm on its side, and the plant will naturally find its way to the surface.
Do I need to start my begonia corms indoors?
While you can plant them directly outside once the soil is warm and all frost danger has passed, starting them indoors is highly recommended. Begonias are slow to sprout and grow, often taking two months to reach a blooming size. Starting them inside in March or April ensures you have a full, flowering plant by the time summer arrives.
How deep should I plant the corms in a pot?
Begonia corms should be planted very shallowly. In a pot, you can simply press the corm into the soil so the top is level with the soil surface, or cover it with no more than half an inch of potting mix. Planting them too deep can lead to the corm rotting or failing to sprout through the soil.
How much sun do begonias need to bloom?
Tuberous begonias perform best in partial shade or filtered sunlight. They need some light to produce flowers, but the direct, intense afternoon sun can be too harsh for their delicate leaves and stems. A location that receives morning sun and afternoon shade is usually the perfect balance for most varieties.