Table of Contents
- Introduction
- Identifying the Top and Bottom of a Begonia Tuber
- Why Correct Orientation is Essential for Success
- How to Plant Begonia Tubers Indoors
- Moving Your Begonias into the Garden
- Caring for Tuberous Begonias Through the Season
- Common Begonia Varieties for Home Gardens
- Preparing for Winter: Lifting and Storing Tubers
- Troubleshooting Common Growth Questions
- Conclusion
- FAQ
Introduction
Tuberous begonias are among the most rewarding flowers you can grow in a shaded garden. Their brilliant colors and rose-like petals bring a tropical feel to porches, patios, and flower beds all summer long. At Longfield Gardens, we love how these versatile begonia flower bulbs transform dim corners into vibrant displays of red, yellow, pink, and white.
When you first hold a begonia tuber in your hand, it might look a bit mysterious. Unlike a tulip or a daffodil, it does not have a clear pointed top and a flat bottom. This often leads gardeners to ask exactly which way up they should plant their begonia bulbs to ensure the best results.
This guide will show you how to identify the right side of the tuber and provide the simple steps needed to get your plants off to a healthy start. Whether you are planting in containers or garden beds, getting the orientation right is the first step toward a beautiful season of blooms.
Identifying the Top and Bottom of a Begonia Tuber
Begonia tubers are dark brown, slightly hairy, and shaped like a thick, lumpy disk. Because they do not have a classic "onion" shape, it is common to feel a little uncertain during your first planting session. However, once you know what to look for, the difference between the top and the bottom is easy to spot.
The most reliable way to tell the difference is to look at the shape of the tuber. One side will have a shallow, bowl-like depression. This is the concave or "dished" side. This hollow area is the top of the tuber where the new stems and leaves will emerge.
The opposite side is rounded, similar to the bottom of a bowl. This is the convex or "domed" side. This rounded part is the bottom of the tuber and should always be placed facing down into the soil. Roots will eventually grow from both the bottom and the sides of the tuber to anchor the plant and absorb nutrients.
If you look closely at the center of the hollowed-out top, you may see small, pinkish or reddish bumps. These are called "eyes," much like the eyes on a potato. These are the active growth points. If you see these sprouts, you can be 100% certain that the hollow side faces up.
Key Takeaway: Always plant begonia tubers with the hollow, bowl-shaped side facing up and the rounded, domed side facing down.
What to Do if You Cannot Tell the Difference
Sometimes a tuber is particularly thick or unusually shaped, making the hollow side hard to find. If you are unsure which way is up, do not worry. You can simply place the tuber on its side in the soil. For more detail, see our Tips for Growing Tuberous Begonias.
The plant has a natural ability to sense gravity and light. The stems will eventually grow toward the surface, and the roots will grow downward. Planting on the side is a safe "middle ground" that prevents the plant from being completely upside down while it finds its way.
Why Correct Orientation is Essential for Success
In the gardening world, "right plant, right place" starts with how you put the bulb in the ground. While a begonia planted upside down may eventually struggle to reach the surface, planting it correctly saves the plant a significant amount of energy.
When the hollow side faces up, the sprouts have a direct path to the light. They can emerge from the soil quickly and begin the process of photosynthesis. This leads to a stronger plant and earlier flowers. If the tuber is upside down, the stems must grow downward and then curve all the way around the tuber to find the surface.
This detour can delay the appearance of leaves by several weeks. In some cases, the tender new growth might even rot before it manages to break through the soil. By taking a moment to check the orientation, you ensure that your begonias can focus all their energy on growing lush foliage and large, showy flowers.
How to Plant Begonia Tubers Indoors
Begonias are tropical plants that love warmth but grow quite slowly at first. For most US gardeners, the best way to get the most out of the blooming season is to start the tubers indoors. If you’re filling pots, our Summer Blooming Bulbs for Containers collection is a great place to browse. This gives them a head start of 8 to 12 weeks before the weather is warm enough to move them outside.
Choosing the Right Container and Soil
You do not need a large pot to get started. A shallow tray or small individual pots with drainage holes work perfectly. Drainage is how fast water leaves the soil, and it is the most important factor in keeping begonias healthy.
Use a high-quality, lightweight potting mix. Avoid using heavy garden soil, which can pack down and stay too wet. A mix that contains peat moss or perlite is ideal because it stays fluffy and allows air to reach the developing roots.
The Planting Process
Fill your container with moist potting mix until it is about two inches from the rim. Place your begonia tubers on the surface with the hollow side facing up. You do not need to bury them deeply at this stage.
Press the tubers gently into the soil so they are nestled in, but leave the tops exposed or only very lightly covered with a thin dusting of soil. This helps you monitor the progress of the sprouts and prevents water from pooling in the hollow center of the tuber, which can cause rot.
Light and Temperature
Place the containers in a warm spot with indirect light. A room temperature of 65°F to 75°F is perfect. Begonias do not need bright light until they start showing green leaves, but they do need consistent warmth to "wake up" from dormancy.
Avoid placing them in a drafty window or an unheated garage. The warmth tells the tuber that spring has arrived. Within a few weeks, you will see those small pink bumps turn into tiny green leaves.
Next Steps for Indoor Starting:
- Select a shallow container with plenty of drainage holes.
- Use a light, pre-moistened potting mix.
- Place tubers hollow-side up and press them halfway into the soil.
- Keep the tray in a warm room (65°F+) out of direct sunlight.
- Wait for green sprouts to appear before moving to a brighter spot.
Moving Your Begonias into the Garden
Once the threat of frost has passed and the nighttime temperatures stay consistently above 60°F, your begonias are ready to move outdoors. This transition should be gradual to help the plants adjust to the wind and changing light levels.
Hardening Off
Before planting them in their final home, spend about a week "hardening off" your begonias. Set them outside in a sheltered, shady spot for a few hours each day, gradually increasing their time outdoors. This prevents the leaves from getting scorched by the sun or damaged by the wind.
Selecting the Best Spot
Begonias are famous for their love of shade. In most parts of the US, a location with dappled sunlight or morning sun and afternoon shade is best. For a closer look at light requirements, see our Are Begonias Sun or Shade Plants?.
Soil drainage remains a priority in the garden. If your soil is heavy clay, consider planting your begonias in raised beds or containers. This keeps the tubers safe from sitting in water after a heavy rain.
Final Planting Depth and Spacing
When you move your started plants into the garden or larger pots, plant them so the top of the tuber is covered by about one inch of soil. If you are planting unsprouted tubers directly outdoors, the same depth applies. For spacing tips, see our How Far Apart Should Begonias Be Planted?.
Space the plants about 8 to 12 inches apart. This gives each plant enough room to spread its leaves and ensures good airflow. Airflow helps keep the foliage dry and prevents common issues like powdery mildew.
Caring for Tuberous Begonias Through the Season
Once your begonias are established, they are relatively low-maintenance plants. Success comes down to a few simple habits regarding water and nutrients.
Watering Correctly
The goal is to keep the soil consistently moist but never waterlogged. Begonias have succulent stems that store a lot of water, which makes them somewhat drought-tolerant, but they will bloom much better with regular moisture.
Check the soil with your finger. If the top inch feels dry, it is time to water. When watering, try to direct the flow at the base of the plant rather than over the leaves. This keeps the foliage dry and reduces the risk of fungal problems. If your begonias are in pots, they will dry out faster than those in the ground, so check them daily during the heat of summer.
Feeding Your Plants
Begonias are heavy feeders because they produce so many large flowers over a long period. We recommend using a balanced, water-soluble fertilizer every two to three weeks. Follow the instructions on the product label for the correct dosage. Regular feeding ensures the plant has the energy to keep producing new buds until the first frost.
Deadheading for More Blooms
Deadheading is the process of removing faded or wilted flowers. While many modern begonia varieties are "self-cleaning" (meaning the flowers fall off on their own), manually removing spent blooms keeps the plant looking tidy. It also encourages the plant to put its energy into new blossoms rather than developing seeds.
Key Takeaway: Consistent moisture and regular feeding are the two simple secrets to a spectacular begonia display that lasts all summer.
Common Begonia Varieties for Home Gardens
At Longfield Gardens, we offer several types of begonias to suit different garden styles. Knowing which type you are planting can help you decide where they will look best.
- Roseform and Camellia-Flowered: Upright Double Begonias produce enormous, double blooms that look remarkably like roses. They are stunning in upright containers or at the front of a shaded border.
- Hanging Basket (Pendula): Hanging begonias have a trailing habit. The stems cascade over the edges of pots and baskets, covered in hundreds of smaller flowers. They are perfect for hanging on a porch.
- Non-Stop Begonias: Begonia Non Stop Mix is bred to bloom early and continue without a break.
- Picotee Begonias: Begonia Upright Double Picotee White adds a sophisticated look to any shade garden.
Preparing for Winter: Lifting and Storing Tubers
Tuberous begonias are perennials, but they are not hardy in most of the US (typically only in zones 9-11). In colder climates, you can easily save your tubers and plant them again next year. If you're not sure where your garden falls, check the Hardiness Zone Map.
When to Dig Them Up
Watch the weather in the fall. After the first light frost, the foliage will begin to yellow and die back. This is a signal that the plant is entering dormancy. At this point, stop watering the plants and allow the soil to dry out.
Cleaning and Drying
Carefully lift the tubers from the soil using a garden fork or trowel. Be gentle to avoid bruising the tubers. Cut the stems back to about an inch above the tuber. Brush off any loose soil, but do not wash them with water.
Place the tubers in a cool, dry, and airy spot for about a week. This allows the outer skin to "cure" or harden, which protects the tuber during storage. Once they are dry, the remaining bit of stem will usually fall off easily.
Winter Storage
Store your begonia tubers in a box filled with peat moss, perlite, or shredded paper. Keep the box in a cool, dark, and dry place that stays between 40°F and 50°F. A basement or a cool closet usually works well. Check on them once or twice during the winter to make sure they are not shriveling or showing signs of mold. In the spring, you can start the whole process over again.
Troubleshooting Common Growth Questions
Even for experienced gardeners, a few common questions often pop up during the begonia season. Most issues are easily solved by adjusting one small factor in the plant's environment.
Why Are My Begonias Growing Slowly?
The most common cause of slow growth is cool temperatures. Begonias really wait for the heat of summer to take off. If you started them indoors and they seem stuck, they may just need a bit more warmth or a slightly brighter location. Once the outdoor temperatures stay consistently warm, you will likely see a sudden burst of growth.
Why Are the Flower Buds Falling Off?
If your plant looks healthy but the buds drop before they open, it is often a sign of "bud blast." This usually happens because of extreme temperature swings or inconsistent watering. If the soil stays dry for too long and is then suddenly soaked, the plant may drop its buds. Keeping the moisture levels steady is the best way to prevent this.
What Should I Do About Yellow Leaves?
While yellow leaves in the fall are normal, yellow leaves in mid-summer can indicate that the soil is staying too wet. If your begonias are in a pot, check that the drainage holes are not blocked. If they are in the ground, ensure the area is not receiving runoff from a nearby gutter or downspout.
What to Do Next:
- Monitor soil moisture by checking with your finger daily.
- Move plants to a more sheltered spot if they show signs of wind damage.
- Ensure pots have clear drainage holes to prevent root rot.
- Fertilize every 2-3 weeks to maintain vigorous blooming.
Conclusion
Planting begonia tubers is a simple and rewarding way to bring elegance to the shady parts of your yard. By remembering to plant them with the hollow side facing up, you give your plants the best possible start for the season. Whether you are growing them in a hanging basket on your front porch or in a decorative container on your patio, these flowers offer a long-lasting display of color that few other shade plants can match. For shipping details and timing, review our Shipping Information.
At Longfield Gardens, we take pride in providing high-quality tubers backed by our 100% Quality Guarantee. With a little warmth, consistent water, and the right orientation at planting time, you can enjoy a stunning summer garden that returns year after year.
"Gardening is a journey of simple steps. Getting the basics right—like which way is up—allows you to relax and enjoy the beauty as it unfolds."
We encourage you to try a few different varieties this season to see which colors and shapes best fit your style. Happy planting!
FAQ
What happens if I plant my begonia tubers upside down?
If a begonia tuber is planted upside down, the stems will still try to grow toward the light, but they will have to grow around the tuber to reach the surface. This uses up a lot of the plant's energy and can delay sprouts by several weeks. In some cases, the tender new growth may rot before it reaches the air, so it is always best to check the orientation before covering them with soil.
Do I need to soak begonia tubers before planting?
Soaking is not usually necessary for begonia tubers, and if done incorrectly, it can actually increase the risk of rot. It is much safer to simply plant the tubers in moist potting mix. The tuber will naturally absorb the moisture it needs from the surrounding soil to begin growing roots and sprouts. For more detail, see our How Deep Should You Plant Begonia Tubers?.
How deep should I plant begonia tubers in the garden?
When planting begonias in their final outdoor location, the top of the tuber should be about one inch below the soil surface. If you have already started the tubers indoors and they have leaves, plant them so the top of the root ball is just covered by soil. Planting them too deeply can make it difficult for new stems to emerge and may cause the base of the plant to rot.
Can I plant begonia tubers directly in the ground without starting them indoors?
Yes, you can plant them directly in the garden, but you must wait until the soil is warm and all danger of frost has passed. Because begonias take a long time to begin flowering, plants that are started directly in the ground may not begin blooming until much later in the summer. Starting them indoors in March or April is the best way to enjoy flowers for the longest possible time. For timing guidance, see our When Do You Plant Tuberous Begonias?.