Table of Contents
- Introduction
- Understanding Begonia Tubers
- Choosing the Right Time to Plant
- How to Start Begonia Tubers Indoors
- Selecting the Best Garden Spot
- How to Plant Begonia Tubers Outdoors
- Planting Begonias in Containers and Baskets
- Caring for Your Begonias All Summer
- Handling Common Growth Variations
- Preparing for Winter
- Summary Checklist for Success
- Conclusion
- FAQ
Introduction
Finding flowers that thrive in the shade can sometimes feel like a challenge. While many plants prefer full sun, tuberous begonias are the hidden gems of the shade garden. These plants offer some of the most spectacular, rose-like blooms in the gardening world. At Longfield Gardens, we enjoy how these versatile plants can transform a quiet corner or a covered patio into a burst of color.
Learning how to plant begonia tubers is a rewarding process that any gardener can master. Whether you want to fill hanging baskets with cascading flowers or line your garden beds with upright varieties, the steps are straightforward. This guide will walk you through everything from starting your tubers indoors to ensuring they bloom all summer long.
By focusing on a few simple requirements like soil drainage and proper timing, you can enjoy these tropical beauties in your own yard. This article is designed to help home gardeners achieve success with tuberous begonias, regardless of their experience level.
Understanding Begonia Tubers
Before you get your hands in the dirt, it helps to know what you are working with. If you'd like a broader overview, see our All About Begonias guide. A begonia tuber is a thickened, underground stem that stores energy for the plant. It looks a bit like a brown, hairy potato or a small woody bowl.
One side of the tuber is indented or hollow, while the other side is rounded and smooth. It is important to look closely at your tubers when they arrive. The hollow, concave side is the top where the stems and leaves will emerge. The rounded, convex side is the bottom where the roots will grow.
We ship begonia tubers from our facility in Lakewood, New Jersey, when it is the right time to plant in your specific climate. For shipping details, see our Shipping Information page. Because these are tropical plants, they are sensitive to cold. Most home gardeners in the US grow them as annuals or start them indoors to give them a head start on the growing season.
Choosing the Right Time to Plant
Timing is one of the most important factors when planting begonias. These plants love warmth and will not tolerate frost. If you plant them too early in cold, wet soil, the tubers may struggle or fail to grow.
Starting Indoors for Earlier Blooms
Most gardeners choose to start their begonia tubers indoors about 8 to 12 weeks before the last expected frost date. This extra time allows the plants to develop strong roots and leaves before they ever move outside. By the time the summer heat arrives, your begonias will already be well-established and ready to flower.
Planting Outdoors
If you prefer to plant directly into the garden or outdoor containers, wait until the soil has warmed. A good rule of thumb is to wait until nighttime temperatures consistently stay above 60°F. If the ground is still cold and damp, the tubers are better off staying in their packaging in a cool, dry place for a few more weeks.
Key Takeaway: Start begonia tubers indoors 2-3 months before the last frost to enjoy flowers earlier in the summer.
How to Start Begonia Tubers Indoors
Starting your begonias in a controlled environment is the best way to ensure a healthy start. You do not need a greenhouse to do this successfully. A bright windowsill or a spot under grow lights works perfectly.
Step 1: Prepare Your Containers
You can use individual small pots or shallow trays with drainage holes. Drainage is essential because begonias do not like to sit in soggy soil. Use a high-quality, lightweight potting mix. A mix that contains peat moss or perlite is ideal because it holds moisture without becoming heavy or waterlogged.
Step 2: Position the Tubers
Fill your container with moist potting soil. Place the begonia tuber on the surface with the hollow side facing up. Do not bury the tuber deep in the soil. Instead, simply press it into the mix so the top is just at or slightly below the soil level. Some gardeners prefer to leave the very top of the tuber exposed until sprouts appear.
Step 3: Provide Warmth and Light
Place the containers in a warm spot where the temperature stays around 70°F. They do not need direct sunlight to sprout, but they do need bright, indirect light once the first leaves appear. Avoid placing them in a drafty area or directly against a cold windowpane.
Step 4: Water Carefully
Water the soil around the tuber, but try to avoid getting water inside the hollow "bowl" of the tuber itself. Standing water in that indentation can cause the tuber to rot. Keep the soil lightly moist. It should feel like a wrung-out sponge—damp but not dripping.
What to do next:
- Check your tubers every few days for signs of growth.
- Once stems are an inch tall, move the plants to a brighter location.
- Ensure the soil never dries out completely.
- Wait for multiple sets of leaves before thinking about the outdoors.
Selecting the Best Garden Spot
Once the weather warms up, it is time to move your begonias to their permanent summer home. Right plant, right place is a core principle at Longfield Gardens. Matching the plant’s needs to your garden's conditions will result in the best performance.
Sunlight Requirements
Tuberous begonias are famous for their love of shade. They do best in filtered light or "dappled" shade, and you can read more in our Where to Plant Begonias: Sun or Shade? Expert Guide. They can also handle morning sun, which is less intense than the afternoon heat. If they are exposed to harsh, direct midday sun, their leaves and delicate flower petals may burn.
Soil and Drainage
"Drainage" simply refers to how fast water leaves the soil. Begonias have a shallow root system and are very sensitive to overwatering. If you are planting in the ground, choose a spot where water does not puddle after a rain. If your soil is heavy clay, consider planting in raised beds or containers to give the roots better airflow and drainage. For a broader look at growing conditions, see our How to Plant and Care for Begonias: A Complete Grower's Guide.
Wind Protection
Many begonia varieties, especially the "Dinnerplate" types, produce very large, heavy flowers. These blooms can sometimes weigh down the stems. Choose a location that is protected from strong winds to prevent the stems from snapping or the plants from being knocked over.
How to Plant Begonia Tubers Outdoors
If you are skipping the indoor start and planting directly outside, the process is very similar to container planting. Make sure the threat of frost is completely gone before you begin.
Prepare the Planting Site
Loosen the soil in your garden bed to a depth of about 5 or 6 inches. You can mix in a little compost to help with nutrients and drainage. Use your hands or a small trowel to create a shallow hole.
Spacing and Depth
Space your begonias about 8 to 12 inches apart. This gives each plant plenty of room for its leaves to spread and allows for good air circulation. Just like with indoor planting, place the tuber hollow side up. Cover the tuber with no more than one inch of soil. Planting them too deep can delay sprouting and may lead to rot in wet weather.
Watering In
After planting, give the area a light watering. This helps settle the soil around the tuber and removes any large air pockets. Be gentle so you do not wash away the thin layer of soil covering the tuber.
Key Takeaway: Plant begonias 8-12 inches apart in a shady spot with well-draining soil, ensuring the hollow side faces up.
Planting Begonias in Containers and Baskets
Begonias are perhaps the most popular choice for containers and hanging baskets. Their mounding or cascading growth habits make them perfect for vertical interest.
Choosing a Container
For a single begonia tuber, a 6-inch pot is usually sufficient. If you are using a larger patio planter or a hanging basket, you can plant multiple tubers together. For a 12-inch hanging basket, three tubers will create a full, lush display. Ensure every container you use has at least one drainage hole in the bottom.
Planting for a Full Look
When planting in a basket, you can use the same depth and spacing rules as the garden. However, many gardeners like to plant them slightly closer to create a more immediate impact. Use a high-quality potting mix rather than garden soil. Potting mix is lighter and designed to provide the specific drainage and aeration that container plants need.
The "Trailing" Begonia Tip
If you are planting trailing (Pendula) varieties, you can tilt the tubers slightly toward the edge of the pot when planting. This encourages the stems to grow outward and over the side, creating that beautiful cascading effect more quickly. For a colorful basket option, Begonia Hanging Golden Balcony is ideal for hanging baskets.
Caring for Your Begonias All Summer
Once your begonias are growing, they are relatively low-maintenance. A little consistent care will keep them blooming from mid-summer until the first frost of autumn.
Watering Routine
Water your begonias regularly to keep the soil consistently moist. In the heat of summer, containers and hanging baskets may need water every day. The goal is to avoid a "rollercoaster" of moisture. Do not let the soil get bone-dry, but do not keep it sopping wet either. If you are unsure, stick your finger an inch into the soil; if it feels dry, it is time to water.
Fertilizing for Blooms
Begonias are "heavy feeders," meaning they use a lot of nutrients to produce those large, showy flowers. Start fertilizing once the plant has several sets of leaves. Use a balanced, water-soluble fertilizer every two weeks. Follow the instructions on the product label for the correct dilution. This consistent boost of nutrients will help the plant maintain its vigor throughout the long blooming season. If you want a mixed planting, Begonia Non Stop Mix - Bulk Offer is another bulk option.
Deadheading
"Deadheading" is the process of removing faded or spent flowers. This is not strictly necessary for the health of the plant, but it keeps the display looking tidy. It also encourages the plant to put its energy into producing new buds rather than developing seeds. To deadhead, simply pinch off the flower stem just below the base of the faded bloom.
Supporting Tall Varieties
If you are growing upright varieties with very large flowers, the stems may need a little help. You can use small bamboo stakes or specialized plant supports to keep the stems from leaning. Tie the stems loosely to the stake with soft garden twine to avoid bruising the plant. For a fuller upright planting, Begonia Upright Double Superba Mix - Bulk Offer is a helpful bulk option.
Handling Common Growth Variations
Gardening is a partnership with nature, and results can vary based on your local environment. It is normal to see some differences in how your begonias grow compared to a neighbor's or even from one year to the next.
Slow Starting
If your tubers are taking a long time to sprout, check the temperature. Begonias are slow to "wake up" if the room or soil is below 60°F. Be patient; once they start growing, they usually catch up quickly. Avoid the temptation to overwater a dormant tuber, as this is the most common reason for failure.
Leggy Growth
If your begonias have very long, thin stems with few leaves, they might be reaching for more light. While they love shade, they still need bright, indirect light to grow strong. Try moving your container to a slightly brighter spot or trimming back overhanging branches if they are in the ground.
Heat Stress
During extreme heatwaves, begonias might look a little wilted in the afternoon, even if the soil is moist. This is a natural defense mechanism. They usually perk back up once the sun goes down and the air cools. If the wilting persists, check the soil moisture and ensure they are getting enough shade during the hottest part of the day.
Preparing for Winter
Tuberous begonias are not hardy in most of the United States (Zones 3-8). However, you do not have to buy new tubers every year. You can save them and plant them again next spring. To check your local growing area, use our Hardiness Zone Map.
When to Dig Them Up
Wait until the foliage starts to turn yellow in late autumn or after the first light frost. The cold will tell the plant it is time to go dormant. Cut the stems back to about an inch above the tuber.
Curing and Storing
Carefully lift the tubers from the soil. Gently brush off any large clumps of dirt, but do not wash them with water. Let the tubers sit in a dry, shaded area for a few days to "cure." This dries out the outer skin. Once they feel dry, place them in a box filled with peat moss, sawdust, or shredded paper. Store them in a cool, dark, and dry place (like a basement or closet) where temperatures stay between 40°F and 50°F.
Summary Checklist for Success
To ensure your begonia journey is enjoyable and successful, keep these simple steps in mind:
- Identify the hollow side of the tuber as the top.
- Start tubers indoors 8-12 weeks before the last frost for early color.
- Plant in a shady or dappled light location.
- Use well-draining soil and avoid overwatering the "bowl" of the tuber.
- Feed every two weeks with a balanced fertilizer.
- Keep soil moist but never soggy.
Key Takeaway: Begonias are resilient and rewarding plants; by providing shade, good drainage, and a little food, you can enjoy a season of tropical-looking blooms.
Conclusion
Growing tuberous begonias is a wonderful way to bring color and elegance to the shadier parts of your landscape. By understanding the basics of how to plant begonia tubers—from identifying the right side to ensuring proper drainage—you are well on your way to a successful garden. These plants offer a unique combination of lush foliage and stunning flowers that few other shade-loving plants can match.
At Longfield Gardens, we want to help you feel confident in your garden. Gardening is a journey of observation and small wins, and begonias are a perfect plant for seeing those rewards firsthand. We stand behind the quality of our tubers with our 100% Quality Guarantee. With a little bit of patience and the right environmental conditions, your begonias will provide a breathtaking display all summer long.
We stand behind the quality of our tubers and are here to support you as you grow. If you have questions about your specific garden conditions, we encourage you to Contact Us and start your planting journey today.
FAQ
How deep should I plant begonia tubers?
Begonia tubers should be planted very shallowly. Whether you are planting in a container or a garden bed, cover the top of the tuber with no more than one inch of soil. If you plant them too deep, the sprouts may struggle to reach the surface, or the tuber may rot before it has a chance to grow.
Which way up do I plant a begonia tuber?
Begonia tubers have a distinct "hollow" or indented side and a rounded side. Always plant the hollow side facing up. This is where the stems and leaves will emerge. The rounded side is the bottom, where the roots will develop. If you truly cannot tell which side is which, you can plant the tuber on its side, and the plant will eventually find its way toward the light.
Can tuberous begonias grow in full sun?
Most tuberous begonias prefer partial shade to full shade. They thrive in dappled light or areas that receive only gentle morning sun. In very hot or southern climates, full sun will likely scorch the leaves and cause the flowers to wilt or drop prematurely. If you have a very sunny spot, you might consider other begonia varieties or provide some artificial shade.
Why are my begonia tubers not sprouting?
The most common reason begonia tubers fail to sprout is a combination of cold temperatures and too much water. Begonias need warmth (around 70°F) to "wake up" from dormancy. If the soil is cold and very wet, the tuber may rot. Ensure your pots are in a warm location and that you are keeping the soil lightly moist rather than saturated.