Table of Contents
- Introduction
- Understanding Begonia Tubers
- Choosing the Right Time to Plant
- Selecting the Best Planting Site
- How to Plant Begonia Bulbs Indoors
- Moving Begonias to the Garden
- Essential Care for Growing Begonias
- Specific Tips for Container Gardening
- Troubleshooting Common Growth Issues
- Handling Begonias at the End of the Season
- Conclusion
- FAQ
Introduction
Shady corners of the garden often feel like quiet retreats, but they do not have to be dull. Tuberous begonias are the perfect solution for bringing brilliant, neon-bright color to those dim spaces where other flowers might struggle. At Longfield Gardens, we love how these plants offer a long season of blooms that look like roses or camellias, continuing from midsummer right through the first frost.
This guide will show you exactly how to plant begonia bulbs to ensure you get the most impressive display possible. Whether you want to fill decorative patio pots or brighten up a garden border, these plants are remarkably easy to grow when you get the basics right. We will cover site selection, the proper way to handle tubers, and simple care tips for a season full of flowers.
Growing begonias is an incredibly rewarding way to add professional-level beauty to your yard with very little stress. By following a few simple steps, you can enjoy lush foliage and spectacular flowers all summer long.
Understanding Begonia Tubers
When you receive your begonia bulbs, you will notice they do not look like a traditional tulip or daffodil bulb. They are actually tubers, which are thickened underground stems. They look a bit like a small, brown, hairy potato or a thick, rough cracker.
Just like a potato has "eyes" that sprout, a begonia tuber has growth points. These points are usually clustered in the center of the tuber. It is important to look closely at the shape of the tuber before you start planting. One side is typically indented or "cupped," making it look like a shallow bowl. This is the top side. The other side is rounded or domed, which is the bottom side.
If you find it difficult to tell the sides apart, don't worry. You can simply place the tuber on its side or wait a week or two for the eyes to start swelling. Once you see small pink or white nubs forming, you will know exactly which way is up. Starting with healthy, firm tubers is the first step toward a successful garden.
Choosing the Right Time to Plant
Begonias are tropical plants by nature. They love warmth and are very sensitive to cold temperatures. This means timing is the most important factor when deciding when to get them in the ground, and the Hardiness Zone Map can help you know when to plant.
Starting Indoors for an Early Show
Most gardeners prefer to start their begonia tubers indoors about 8 to 12 weeks before the last expected frost in their area. Because begonias take a few months to go from a dormant tuber to a flowering plant, giving them this "head start" ensures you have big, blooming plants by the time summer arrives.
If you live in a northern climate with a short growing season, starting indoors is highly recommended. It allows the plant to develop a strong root system and several sets of leaves in a protected environment. By the time the weather is warm enough to move them outside, they will be ready to explode with color.
Planting Directly Outdoors
You can plant begonia tubers directly into the garden or outdoor containers, but you must wait until the danger of frost has completely passed. The soil needs to be warm—ideally around 60°F. If the soil is too cold and wet, the tubers may stay dormant or struggle to grow.
In most regions, this means waiting until late May or early June. If you choose this method, your begonias will likely start blooming later in the summer compared to those started indoors. However, they will still provide a wonderful show through the autumn months.
Selecting the Best Planting Site
Begonias have specific preferences for light and soil. Following the "right plant, right place" rule will make your gardening much easier and more successful.
Light Requirements
The most common mistake with begonias is giving them too much sun. These plants are famous for their ability to thrive in partial shade. In fact, in most parts of the United States, begonias need protection from the hot afternoon sun.
Dappled light under a tall tree or a spot that gets gentle morning sun and afternoon shade is perfect. If the leaves look like they are turning brown or "crispy" at the edges, they are likely getting too much direct light. On the other hand, if the plant becomes very leggy and produces few flowers, it might need just a little more brightness.
Soil and Drainage
Drainage is a term gardeners use to describe how fast water leaves the soil. Begonias need excellent drainage. They like to stay moist, but they cannot sit in soggy soil. If the tuber sits in water for too long, it can rot.
If you are planting in the ground, look for a spot where water does not puddle after a rainstorm. You can improve heavy clay soil by mixing in some compost or finely ground bark. For container gardening, always use a high-quality potting mix rather than garden soil. Potting mix is light and airy, which helps the roots breathe and allows excess water to run out of the drainage holes at the bottom of the pot.
Key Takeaway: Choose a spot with filtered light and soil that allows water to move through easily. Avoid heavy sun and standing water to keep your tubers healthy.
How to Plant Begonia Bulbs Indoors
Starting your begonias in trays or small pots indoors is a fun way to kick off the spring season. It is a simple process that requires just a few supplies.
Step 1: Prepare Your Containers
You can use individual 4-inch pots or a shallow nursery tray. Ensure whatever you use has holes in the bottom for drainage. Fill the containers with a light, pre-moistened potting mix. It should feel like a wrung-out sponge—damp but not dripping.
Step 2: Placement and Depth
Place the tuber onto the soil surface with the indented (hollow) side facing up. You do not need to bury them deeply. In fact, many experts suggest leaving the top of the tuber just barely visible or covered by only a half-inch of soil. This prevents water from sitting in the hollow center of the tuber, which can lead to rot.
Step 3: Space Them Out
If you are using a large tray to start multiple tubers, space them about 2 to 3 inches apart. If you are planting them directly into their final decorative pots, you can space them closer to their mature distance, which is usually 8 to 12 inches apart depending on the variety.
Step 4: Warmth and Light
Begonias do not need light to start growing, but they do need warmth. A room temperature of 65°F to 70°F is ideal. You can place the trays on top of a refrigerator or use a gentle heat mat to speed up the process. Once you see green sprouts emerging, move the containers to a bright window or under grow lights.
What to do next:
- Check the soil every few days; keep it lightly moist.
- Avoid overwatering before the sprouts appear.
- Watch for the first pink or green "eyes" to emerge from the center.
- Ensure they have plenty of bright, indirect light once leaves appear.
Moving Begonias to the Garden
Once the weather warms up and your indoor-started begonias have several leaves, it is time to think about moving them outside. This transition should be gradual to avoid shocking the plants.
Hardening Off
The process of getting plants ready for the outdoors is called "hardening off." Start by placing your pots in a sheltered, shady spot outside for just an hour or two during the day. Gradually increase the time they spend outside over the course of a week. This allows the leaves to toughen up and get used to the wind and shifting light.
Transplanting into the Ground
If you are moving your begonias from indoor trays to a garden bed, dig a hole that is slightly larger than the root ball. Carefully remove the plant from its starter container, keeping as much soil around the roots as possible. Set the plant in the hole so the top of the root ball is level with the surrounding soil.
Backfill the hole with soil and press down very gently with your hands to remove large air pockets. Water the area immediately to help settle the roots into their new home.
Spacing for Success
Give your begonias room to breathe. Hanging Begonias are a good choice if you are planting a trailing variety in a hanging basket. Most tuberous begonias should be spaced about 10 to 12 inches apart. Good air circulation is a simple way to prevent common issues like powdery mildew, which is a white, dusty-looking fungus that can grow on leaves in humid conditions. If you are planting a trailing variety in a hanging basket, you can tuck 2 or 3 tubers into a 12-inch pot for a full, lush look.
Essential Care for Growing Begonias
Once your begonias are settled in, they are relatively low-maintenance. Getting a few basic care habits right will ensure they bloom continuously until the first frost.
Watering Correctly
The goal is to keep the soil consistently moist but never waterlogged. In the heat of summer, containers and hanging baskets may need water every day. Plants in the ground usually need water less often.
A good rule of thumb is to stick your finger an inch into the soil. If it feels dry, it is time to water. Always try to water at the base of the plant rather than splashing the leaves. Wet leaves in the shade can lead to spots or fungal growth.
Fertilizing for Blooms
Begonias are "heavy feeders," meaning they use a lot of energy to produce those massive, colorful flowers. We recommend using a balanced, water-soluble fertilizer every two weeks during the growing season.
Look for a fertilizer with a balanced ratio, such as 10-10-10, or one specifically formulated for flowering plants. Always follow the instructions on the label. If you are using a potting mix that already contains slow-release fertilizer, you may only need to supplement occasionally in midsummer.
Deadheading and Grooming
"Deadheading" is the process of removing faded flowers. Many modern begonia varieties, such as Nonstop begonias, are self-cleaning, meaning the old flowers fall off on their own. However, if you see spent blooms hanging on the plant, you can gently pinch them off to keep the plant looking tidy.
If your begonias start to look a bit "leggy" or stretched out, do not be afraid to pinch back the tips of the stems. This encourages the plant to branch out and become bushier, which ultimately leads to more flowers.
Specific Tips for Container Gardening
Begonias are perhaps the most popular choice for shade containers because they offer such a wide variety of growth habits. From upright, bushy types to cascading varieties that spill over the edges, there is a begonia for every pot.
Hanging Baskets
For hanging baskets, look for "pendula" or Pink Balcony. These are bred to have flexible stems that drape beautifully. When planting these, you can tilt the tubers slightly toward the edge of the pot to encourage them to grow outward and downward more quickly.
Because hanging baskets are exposed to more wind and air, they dry out faster than pots on the ground. Check them daily. If the basket feels light when you lift it, it needs a deep watering.
Window Boxes and Patio Pots
In window boxes, upright double begonias play well with other shade-lovers. You can pair them with trailing lobelia, coleus, or ivy. When mixing plants, just make sure they all have the same "low-to-medium" light requirements. Using a high-quality potting mix at Longfield Gardens ensures that your container begonias have the nutrient-rich, airy environment they need to thrive in a cramped space.
Key Takeaway: Containers offer more control over soil and light, but they require more frequent watering and regular feeding to keep the plants looking their best.
Troubleshooting Common Growth Issues
While begonias are generally easy to grow, you might run into a few common questions. Most issues can be solved by adjusting one variable at a time.
Why Are the Buds Falling Off?
If your begonia is dropping its flower buds before they open, it is usually a sign of stress. The most common causes are extreme heat or inconsistent watering. If the weather is very hot, try moving your pots to a cooler, shadier spot. Ensure you are not letting the soil dry out completely between waterings.
Yellow Leaves
Yellowing leaves can be a sign of too much water. If the soil feels soggy, stop watering for a few days and let it dry out. Check to make sure your pot's drainage holes are not blocked. If the soil is not too wet, yellow leaves might mean the plant needs a bit more fertilizer.
Slow Growth
If your tubers are taking a long time to sprout, check the temperature. Begonias are slow to wake up if the room is below 60°F. Sometimes a little extra warmth is all they need to get moving. Also, remember that begonias naturally take about 3 months to reach their full flowering potential, so patience is part of the process.
Handling Begonias at the End of the Season
As the days get shorter and the weather cools, begonias will naturally start to slow down. In most parts of the US (Zones 2 through 8), begonias will not survive the winter outdoors.
Recognizing Dormancy
When the leaves start to turn yellow and the plant looks like it is "tiring out," it is entering dormancy. This usually happens after the first light frost kills the top growth. At this point, you can cut the stems back to about an inch above the soil.
Storing Tubers for Next Year
One of the best things about begonias is that you can save the tubers and plant them again next spring. Carefully dig up the tubers and let them dry in a cool, shaded spot for a few days. Brush off the excess soil and store them in a box filled with dry peat moss or sawdust.
Keep the box in a cool, dark, dry place that stays between 40°F and 50°F (like a basement or a cool closet). Next spring, you can pull them out and start the planting process all over again.
Conclusion
Planting begonia bulbs is one of the easiest ways to transform a shady yard into a vibrant garden. By choosing the right spot with filtered light, ensuring good drainage, and giving your tubers a warm head start indoors, you set the stage for a spectacular summer. These plants are incredibly resilient and offer a range of colors and shapes that few other shade plants can match.
At Longfield Gardens, we believe that everyone can have a beautiful garden regardless of their skill level. Begonias are the perfect example of a plant that rewards a little bit of care with a whole lot of beauty. Whether you are planting a single pot for your porch or a long border along a shaded path, the results will be well worth the effort.
- Wait for warm weather or start indoors 8-12 weeks before frost.
- Plant the indented side of the tuber facing up.
- Provide partial shade and well-drained soil.
- Water consistently and fertilize every two weeks.
Growing your own flowers from tubers is a journey that brings color and joy to your home season after season. Get started today and watch your shade garden come to life.
FAQ
Which side of the begonia tuber should face up when planting?
The indented or "cupped" side of the tuber should always face up. This is where the growth points, or "eyes," are located. The rounded, smooth side is the bottom and should be placed against the soil.
When is the best time to move my begonias outside?
You should only move begonias outside when the danger of frost has completely passed and nighttime temperatures stay consistently above 50°F. These plants are tropical and will be damaged by cold snaps or chilly soil.
Can I plant begonias in full sun?
In most regions, begonias prefer partial shade or filtered light, especially in the afternoon. If you live in a very cool, northern climate, they may tolerate more sun. However, in the South or during hot summers, full sun will often burn the leaves and cause the flowers to wilt.
How deep should I plant begonia bulbs?
Begonia tubers should be planted quite shallowly. Place them on the soil surface and cover them with only about a half-inch of potting mix. If you are starting them indoors, you can even leave the very tops of the tubers exposed until you see sprouts, then add a light layer of soil.