Table of Contents
- Introduction
- The Short Answer: When to Plant
- Why an Early Start Matters
- Planting Timing by USDA Hardiness Zone
- How to Wake Up Your Begonia Tubers
- Starting Begonias Indoors: Step-by-Step
- Moving Begonias Outdoors
- Right Plant, Right Place: Sun and Soil
- Popular Begonia Varieties to Consider
- Summer Care for Maximum Blooms
- What to Do at the End of the Season
- Troubleshooting Common Issues
- Safety and Expectations
- Conclusion
- FAQ
Introduction
There is a special kind of magic in watching a shady corner of the garden transform into a lush, colorful retreat. If you have been looking for a way to add brilliant color to your porch, patio, or woodland borders, tuberous begonias are a perfect choice. These tropical beauties produce some of the most spectacular flowers in the gardening world, ranging from delicate, rose-like petals to massive, ruffled blooms. At Longfield Gardens, we love helping gardeners discover how easy it is to grow these showstoppers, even in those tricky spots where other flowers might struggle to find enough light.
The key to a successful begonia season starts with one simple factor: timing. Because begonias are native to tropical climates, they are quite sensitive to the cold. Getting the timing right ensures your plants stay healthy and have plenty of time to develop their gorgeous flowers. This article will explain exactly when to plant your begonia tubers, whether you are starting them indoors for an early head start or waiting to plant them directly in your garden beds. For a closer look at timing, see our When to Plant Begonias Outdoors guide.
Understanding the relationship between temperature and growth will give you the confidence to plant at the perfect moment. Whether you are a first-time gardener or an experienced enthusiast, these timing tips will help you enjoy a long season of beautiful blooms.
The Short Answer: When to Plant
The best time to plant begonia tubers depends entirely on your local climate and whether you plan to start them indoors or outside. Generally, these plants need warm soil and no risk of frost to thrive. If you are planting directly into the garden, you must wait until the soil is warm and the danger of frost has completely passed.
For most gardeners in the United States, this means planting outdoors in late May or early June. However, begonias have a relatively long growing season. If you wait until June to plant, you might not see flowers until late summer. To get the most out of your begonias, we recommend starting them indoors about 8 to 12 weeks before your area's average last frost date.
Starting early gives the tubers time to "wake up" and develop sturdy stems and leaves. By the time the weather is warm enough to move them outside, you will have established plants ready to bloom. This head start can lead to a much longer flowering season, often lasting from mid-summer straight through to the first frost of autumn.
Why an Early Start Matters
Tuberous begonias are not in a hurry. From the moment you plant a dormant tuber, it can take several weeks for the first sprouts to appear. After that, it usually takes another 12 to 14 weeks for the plant to begin flowering. If you live in a region with a short growing season, starting them indoors is the best way to ensure you get plenty of bloom time.
When you start your tubers indoors during late winter or early spring, you are essentially mimicking the tropical conditions they love. A warm mudroom, a sunny windowsill, or a spot under grow lights provides the perfect environment for early growth. This controlled environment protects the young sprouts from the unpredictable swings of early spring weather.
The goal of an early start is to have a well-developed plant by the time the outdoor temperatures are consistently warm. Begonias that start the season with several sets of leaves are much more resilient than small sprouts. They can better handle the transition to the outdoors and will reach their peak flowering potential much sooner.
Key Takeaway: Start begonia tubers indoors 8 to 12 weeks before the last frost to enjoy the longest possible blooming season.
Planting Timing by USDA Hardiness Zone
Because the "last frost" varies wildly across the country, it helps to look at timing based on your specific USDA hardiness zone. At Longfield Gardens, we use these zones to help determine the best shipping and planting windows for our customers. Here is a general timeline for when to start your begonias indoors based on where you live:
- Zones 3 and 4: Start indoors in late March or early April. Move outdoors in early to mid-June.
- Zones 5 and 6: Start indoors in mid-March. Move outdoors in late May.
- Zone 7: Start indoors in late February. Move outdoors in late April or early May.
- Zone 8: Start indoors in early February. Move outdoors in early April.
- Zone 9: Start indoors in early January. Move outdoors in early March.
- Zone 10: Start indoors in late December. Move outdoors in February.
If you are unsure of your hardiness zone, you can find it easily by looking up your zip code on a USDA zone map. Keep in mind that these are general guidelines. Local weather patterns can change from year to year, so it is always a good idea to keep an eye on your local 10-day forecast before moving plants outside.
How to Wake Up Your Begonia Tubers
When you first receive your begonia tubers, they will likely be dormant. They often look like small, brown, hairy disks or bowls. Before they go into the soil, you may want to "wake them up." This is a simple process that helps the tuber start growing more quickly once it is planted. If you want a broader overview of the plant family, see our All About Begonias guide.
To wake them up, place the tubers on a tray in a warm room with bright, indirect light. Make sure the hollow or "bowl" side is facing up. Within a week or two, you should see small, pinkish buds (called "eyes") beginning to swell inside the hollow area. These eyes will eventually grow into the stems and leaves of your plant.
Once you see these sprouts reaching about a half-inch in height, it is the perfect time to move them into containers. If you don't see sprouts right away, don't worry. Some varieties take a little longer to break dormancy than others. As long as the tuber feels firm and not soft or mushy, it is healthy and just needs a bit more time.
Starting Begonias Indoors: Step-by-Step
Starting your begonias indoors is a rewarding late-winter project. You don't need a professional greenhouse to be successful. A few simple supplies and a little bit of patience are all it takes. If you want a more detailed walk-through, our How Do You Plant Begonia Tubers? guide covers the basics.
Choose the Right Container
For the initial starting phase, you can use shallow trays, peat pots, or small plastic nursery pots. Ensure every container has drainage holes. Begonias love moisture, but they cannot sit in water, or the tubers may rot.
Use Quality Potting Mix
Select a light, well-draining potting soil. Avoid using heavy garden soil, which can pack down too tightly in containers. Moisten the soil slightly before you begin planting so it is damp but not dripping wet.
Planting Depth and Direction
This is the most important part of the process. Place the tuber into the soil with the hollow (concave) side facing up. The rounded (convex) side is the bottom where the roots will grow.
- Depth: Cover the tuber with only about a half-inch to one inch of soil.
- Spacing: If you are starting several in a tray, space them about 3 inches apart.
Warmth and Light
Place your containers in a warm spot, ideally between 70°F and 75°F. You can cover the pots loosely with clear plastic wrap to help retain humidity, but remove it as soon as you see green growth. Once the sprouts emerge, move the pots to a bright window or place them under grow lights.
What to Do Next: Early Care
- Keep the soil consistently moist but never soggy.
- Allow the top of the soil to dry slightly between waterings.
- Provide at least 12 to 14 hours of light if using grow lights.
- Avoid fertilizing until the plant has several sets of leaves.
Moving Begonias Outdoors
The transition from the cozy indoors to the garden is a big step for a young plant. Begonias are particularly sensitive to "transplant shock" if the change happens too quickly. Proper timing for this move is just as important as the initial planting date. Our Can a Begonia Be Planted Outside? Your Easy Summer Guide goes into the transition in more detail.
Check the Temperatures
Wait until the threat of frost is completely gone. More importantly, wait until nighttime temperatures are consistently above 50°F. If the nights are still chilly, the plants may stop growing or develop yellow leaves. Begonias are happiest when the air is warm and the soil has reached at least 60°F.
The Hardening Off Process
Before you plant them in their permanent summer home, you must "harden them off." This means gradually introducing them to outdoor conditions.
- Start by placing the pots in a sheltered, shady spot outside for a few hours during the day.
- Bring them back inside at night.
- Over the course of a week, slowly increase the amount of time they spend outside and gradually expose them to a little more light.
- After 7 to 10 days of this transition, they should be ready to stay out for good.
Planting in the Garden or Large Pots
If you are moving them into garden beds, space the plants about 8 to 12 inches apart. For large containers or hanging baskets, you can plant 2 or 3 tubers in a 12-inch pot for a full, lush look. Be very gentle when handling the plants, as the stems are succulent and can snap easily.
Key Takeaway: Consistency is key. Ensure nighttime temperatures stay above 50°F before moving begonias to their permanent outdoor location.
Right Plant, Right Place: Sun and Soil
While timing gets the plants started, the right location keeps them blooming all summer long. Begonias are famous for their love of shade, but they do need some light to produce flowers. For more help matching a begonia to the right spot, see our Where to Plant Begonia for Beautiful Blooms and Foliage guide.
Light Requirements
Most tuberous begonias prefer dappled shade or indirect light. A spot that gets gentle morning sun and then afternoon shade is usually ideal. In very hot climates, they may need almost full shade to prevent the leaves from scorching. If your begonias are not blooming well, they might need a bit more light. If the leaves look brown and crispy at the edges, they are likely getting too much sun.
Soil and Drainage
Begonias have fine, delicate root systems. They need soil that is rich in organic matter but stays loose enough for water to drain away quickly. If you are planting in the ground, adding some compost or leaf mold can help improve the soil structure. For containers, a high-quality potting mix with perlite or vermiculite works best.
Protection from Wind
The stems and heavy blooms of begonias can be somewhat fragile. Choosing a location that is protected from strong winds will prevent the stems from breaking. If you are growing upright varieties that get quite tall, you might consider using small bamboo stakes for extra support.
Popular Begonia Varieties to Consider
At Longfield Gardens, we offer a variety of begonias that suit different garden needs. Knowing which type you are planting can help you decide where to put them.
- Roseform Begonias: These are the classic upright types with large, double flowers that look exactly like roses. They are perfect for garden borders and upright containers.
- Hanging Basket (Pendula) Begonias: These varieties have a cascading habit. Their stems drape over the sides of pots, making them the best choice for hanging baskets and window boxes.
- Picotee Begonias: These stunning flowers feature petals with a contrasting color on the edges. They add a sophisticated, two-toned look to the garden.
- Fimbriata Begonias: These have unique, fringed petals that resemble carnations. They add a lot of texture to shade displays.
- Scentiment Begonias: Unlike many other types, these varieties are prized for their lovely fragrance.
Summer Care for Maximum Blooms
Once your begonias are established in their summer home, they are relatively low-maintenance. However, a few simple tasks will keep them looking their best until the end of the season.
Watering Correctly
Water your begonias at the base of the plant to keep the foliage dry. This helps prevent fungal issues like powdery mildew. The goal is to keep the soil moist but not saturated. In the heat of summer, containers may need water every day, while garden beds may only need it every few days.
Fertilizing
Begonias are "heavy feeders," meaning they use a lot of energy to produce those big flowers. Use a balanced, water-soluble fertilizer every two weeks during the growing season. This provides the nutrients they need to keep pumping out new buds. Always follow the instructions on the fertilizer label for the best results.
Deadheading
"Deadheading" is the practice of removing old, faded flowers. This not only keeps the plant looking tidy but also encourages it to put its energy into new blooms rather than seed production. Simply pinch off the spent flower head just below the bloom.
What to Do at the End of the Season
As the days grow shorter and temperatures drop in the fall, your begonias will begin to slow down. Because they are tropical plants, they will not survive a hard freeze. If you live in a cold climate (Zones 3-8), you will need to bring the tubers inside if you want to grow them again next year.
Wait until the foliage starts to turn yellow or until after the first very light frost. The cold signal tells the plant it is time to go dormant. Cut the stems back to about an inch above the tuber. Carefully dig up the tubers, being sure not to nick or bruise them.
Shake off the excess soil and let the tubers dry in a warm, dry place for about a week. Once they are dry, store them in a cool, dark, and dry location. A cardboard box filled with peat moss, sawdust, or even wrapped in newspaper works well. Ideally, the storage temperature should be between 40°F and 50°F.
Troubleshooting Common Issues
If your begonias aren't performing as expected, the solution is usually found in the basics of sun, water, or temperature.
No Blooms
If the plant looks healthy and green but isn't flowering, it is likely not getting enough light. Try moving the pot to a slightly brighter spot. Also, ensure you are using a fertilizer that promotes blooming (one with a slightly higher middle number, which represents phosphorus).
Yellow Leaves
Yellow leaves can be a sign of a few different things. Most often, it is a result of overwatering or poor drainage. If the soil feels soggy, let it dry out more between waterings. Yellowing can also happen if the temperatures drop too low at night.
Drooping Stems
In very hot or humid weather, begonias can sometimes look a bit wilted or droopy in the afternoon. Usually, they will perk back up once the sun goes down. If the drooping persists, check the soil moisture. If the soil is wet and the plant is wilting, it could be a sign of root issues, so reduce watering immediately.
Safety and Expectations
It is important to remember that while gardening is a joyful activity, some plants require a bit of caution. Begonia tubers and foliage can be toxic if ingested by pets or children. It is always a good idea to keep the tubers out of reach during the planting and storage phases. If you have curious pets, consider placing your begonias in hanging baskets or on high plant stands.
Also, keep in mind that every garden is a unique microclimate. While we provide general timelines, your specific soil, sun exposure, and local weather will influence how fast your begonias grow. Some years spring arrives early, and other years it lingers. Being flexible and observing your plants is the best way to become a successful gardener.
Conclusion
Planting begonias is one of the most rewarding ways to bring life and vibrant color to the shaded areas of your yard. By starting your tubers indoors in late winter and waiting for the warm weather of late spring to move them outside, you set the stage for a spectacular summer display. These plants may take a little time to get started, but the reward of those lush, rose-like blooms is well worth the wait.
Our team at Longfield Gardens is dedicated to providing high-quality tubers and the practical advice you need to grow them with confidence. Whether you choose the cascading beauty of a hanging basket variety or the bold presence of a Roseform upright, begonias are sure to become a favorite in your summer garden.
- Start tubers indoors 8-12 weeks before the last frost for early blooms.
- Wait for nighttime temperatures to stay above 50°F before moving plants outside.
- Provide dappled shade and well-draining soil.
- Feed regularly with a balanced fertilizer throughout the summer.
Ready to transform your shade garden? Take the next step by exploring the wide variety of colors and textures available at Longfield Gardens and start planning your most beautiful season yet.
FAQ
Can I plant begonia tubers directly in the ground?
Yes, you can plant them directly outdoors once the soil is warm and all danger of frost has passed. However, because they take several months to bloom, planting them directly outside often results in a very short flowering season. Starting them indoors is the best way to enjoy flowers for a longer period.
Which way is "up" when planting a begonia tuber?
Begonia tubers have a distinct shape that helps you identify the top. One side is rounded (the bottom), and the other side has a hollow, bowl-like indentation (the top). Always plant the tuber with the hollow side facing upward, as this is where the stems will sprout. For a step-by-step visual, see our How Do You Plant Begonia Tubers? guide.
Why are my begonia tubers taking so long to sprout?
Begonias are naturally slow starters and require consistent warmth to break dormancy. If your room is cooler than 70°F, sprouting may take longer. Ensure the soil is damp but not wet, and be patient; it often takes 3 to 6 weeks to see significant green growth above the soil.
Do I need to soak begonia tubers before planting?
Soaking is not strictly necessary for begonia tubers, though some gardeners find that a brief 30-minute soak in room-temperature water helps "wake them up." Most people find success by simply placing the tubers on a warm tray or planting them in moist soil to trigger growth.