Introduction
Shade gardens often feel like a quiet retreat, and nothing brings them to life quite like the brilliant colors of tuberous begonias. These plants are famous for their large, rose-like blooms and lush foliage, making them a favorite for porch containers and garden beds alike. At Longfield Gardens, we enjoy helping people discover how easy it is to grow these tropical beauties from a simple tuber in our Begonia Flower Bulbs for Sale collection.
This guide focuses on the specific steps you need to take to plant begonia tubers correctly. Whether you are starting them indoors to get a head start on summer or waiting for the warm spring soil, the process is straightforward and rewarding. We will walk you through site selection, tuber orientation, and the best ways to keep your plants healthy.
By following a few basic rules about soil moisture and planting depth, you can ensure your begonias thrive throughout the season. The key to success is providing a warm environment and making sure you place the tuber in the soil with the correct side facing up.
Understanding Begonia Tubers
Before you get your hands in the dirt, it helps to understand what a begonia tuber actually is. If you want a broader overview, see our All About Begonias guide. Unlike a round tulip bulb or a long lily bulb, a begonia tuber looks a bit like a dark, hairy potato or a thick, brown cracker. It is a specialized underground stem that stores energy for the plant.
When you look closely at a tuber, you will notice it has a distinct shape. One side is usually indented or "dished," while the other side is rounded or "domed." This shape is the most important thing to notice when you are ready to plant. The indented side is where the new growth will emerge.
Begonias are tropical plants, which means they love warmth and humidity. They are not frost-hardy, so the tubers need to be treated with care in most US climates. Because they have a relatively long growing season, many gardeners choose to start them indoors. This gives the plants enough time to develop strong stems before they face the summer heat.
Upright vs. Hanging Begonias
When deciding how to plant your tubers, think about the space you want to fill. We offer several types of begonias that serve different purposes in the garden:
- Upright Begonias: These grow on sturdy, vertical stems. They are perfect for garden borders or large patio pots. Varieties like the Bouton de Rose or the ruffled Fimbriata types fall into this category.
- Hanging Basket (Pendula) Begonias: These have a more relaxed, cascading habit. They are specifically bred to spill over the sides of containers and hanging baskets.
- Picotee Begonias: These are known for their stunning bi-color petals, often with a contrasting edge, like Picotee White. They come in both upright and trailing forms.
Key Takeaway: Identify the indented "bowl" side of your tuber before planting. This side must face up toward the sky to allow sprouts to reach the light.
When to Start Your Begonia Tubers
Timing is everything when it comes to begonias. Because they take about 12 to 15 weeks to go from a dry tuber to a fully blooming plant, starting early is a great strategy.
Starting Indoors for Early Blooms
In most parts of the United States, we recommend starting begonia tubers indoors about 8 to 12 weeks before the last expected frost date. For a local guide, see our When to Plant Begonias Outdoors article. Starting them in a warm, indoor environment allows the tubers to "wake up" and begin growing roots and stems while the ground outside is still cold.
If you wait to plant them directly in the garden until after the frost has passed, you might not see flowers until late in the summer. Starting indoors ensures you get a full season of color from June all the way through the first autumn frost. If you're planning to order, our Shipping Information page explains how delivery timing works by zone.
Planting Directly Outdoors
If you prefer to plant directly into the ground or outdoor containers, you must wait until the soil is warm and the danger of frost is completely gone. Begonias are very sensitive to cold. We suggest waiting until nighttime temperatures are consistently above 60°F before moving begonias outside or planting them in the garden.
Choosing the Best Planting Site
Begonias are famous for their ability to brighten up the shade. However, "shade" can mean different things depending on your climate.
Light Requirements
In general, begonias prefer partial shade or dappled sunlight. For more light guidance, see our Where to Plant Begonia for Beautiful Blooms and Foliage guide. They love the soft light found under a tall tree or on a covered porch.
- Morning Sun: In cooler northern climates, begonias often enjoy a few hours of direct morning sun followed by afternoon shade.
- Deep Shade: In very hot southern climates, they need protection from the intense midday and afternoon sun to prevent their leaves from scorching.
- Indirect Light: If you are starting them indoors, a bright window with indirect light is perfect.
Soil and Drainage
The most common reason a begonia tuber fails to grow is "wet feet." Like a sponge, the tuber can absorb too much water and begin to rot if the soil stays soggy. For more planting advice, see Can You Plant Begonias in the Ground?
- Well-Draining Soil: Use a high-quality potting mix that is light and porous. Look for mixes that contain peat moss or perlite, which help hold moisture without becoming waterlogged.
- Garden Soil: If planting in the ground, ensure the area does not collect standing water after a rain. If your soil is heavy clay, we suggest adding organic matter like compost to improve the drainage.
How to Plant Begonia Tubers Indoors: Step-by-Step
Starting your begonias in containers is the most reliable way to get them growing. You can use individual 6-inch pots or a shallow tray if you plan to move them later.
1. Prepare Your Containers
Ensure your pots or trays have plenty of drainage holes. Begonias need water to leave the pot quickly. Fill the container with a pre-moistened potting mix, leaving about two inches of space at the top.
2. Identify the Top of the Tuber
Look for the indented, hollow side. This is the top. For a closer look at tuber orientation, see How to Plant Tuberous Begonias: Which End Is Up?. Sometimes you may see small pink or white "buds" already starting to peek out from the hollow area. These are the eyes of the tuber. If the tuber is very round and you cannot tell which side is which, you can place it on its side, and the plant will figure out the right way to grow.
3. Place and Cover
Set the tuber on the surface of the soil with the hollow side facing up. Do not bury it deep. Begonia tubers only need a very thin layer of soil over them—usually about half an inch. Some gardeners prefer to leave the very top of the tuber exposed until the first sprouts appear, then add a light dusting of soil.
4. Space Them Correctly
If you are planting multiple tubers in a large container or tray, space them about 2 to 4 inches apart. They need a little room for their roots to spread without tangling with their neighbors.
5. Water Carefully
After planting, water the soil lightly to settle it around the tuber. Avoid pouring water directly into the hollow "cup" of the tuber, as standing water there can cause rot. Instead, water the soil around the edges of the tuber.
What to Do Next:
- Place your pots in a warm spot (about 70°F).
- Keep the soil slightly damp, like a wrung-out sponge.
- Wait 2–4 weeks for the first sprouts to appear.
- Provide bright, indirect light once green leaves emerge.
Moving Begonias to the Garden
Once your begonias have grown a few inches tall and the weather outside is warm, it is time to move them to their permanent summer home.
The Hardening Off Process
You cannot move a plant from a cozy indoor environment directly into the wind and sun without a transition period. This is called "hardening off." If you need a refresher, see our Can a Begonia Be Planted Outside? guide.
- On a warm day, set your pots outside in a shaded, protected area for a few hours.
- Bring them back inside at night.
- Each day, leave them out a little longer and gradually expose them to a bit more light.
- After about a week of this, they will be ready to stay outside permanently.
Planting in the Ground
When planting begonias in a garden bed, dig a hole just large enough to accommodate the root ball. Space the plants about 8 to 12 inches apart. For more spacing ideas, see How Far Apart Do You Plant Begonias? This gives them enough room to grow into full, bushy plants without overcrowding, which helps with air circulation. Air movement is important for preventing mildew on the leaves.
Planting in Containers and Baskets
For a standard 12-inch hanging basket, we recommend planting three Begonia Hanging Pink Balcony tubers. This creates a full, lush look as the stems grow and begin to drape over the sides. If you are using upright begonias in a patio pot, one large tuber per 8-inch pot usually provides a beautiful display.
Ongoing Care and Maintenance
Begonias are relatively low-maintenance once they get settled, but they do have a few specific needs to stay looking their best.
Watering Rules
The goal is to keep the soil consistently moist but never saturated.
- Check the Soil: Stick your finger about an inch into the soil. If it feels dry, it is time to water.
- Container Care: Pots and hanging baskets dry out much faster than the ground. In the heat of summer, you may need to water your containers every day. For a fuller care checklist, see How to Care for Begonia Plants for Stunning Color.
- Avoid the Foliage: Try to water the base of the plant rather than the leaves. Wet leaves can lead to fungal issues in humid weather.
Fertilizing for Blooms
Begonias are "heavy feeders," meaning they use a lot of energy to produce those giant flowers. We recommend using a balanced, water-soluble fertilizer every two weeks during the growing season. For more fertilizer timing tips, see Tips for Growing Tuberous Begonias. This provides a steady supply of nutrients to keep the foliage green and the blooms coming. Follow the instructions on the fertilizer label for the correct mixing ratio.
Deadheading and Grooming
To keep your plants looking tidy, remove flowers as they begin to fade. This is called "deadheading." It encourages the plant to put its energy into making new blossoms rather than seeds. If you notice any yellowing or damaged leaves, simply snip them off at the base of the stem.
Key Takeaway: Consistent moisture and regular feeding are the two most important factors for maintaining vibrant begonia blooms all summer long.
Common Questions About Planting Begonias
When you are learning how to plant begonia tubers, it is natural to have a few questions about the process. Here are some of the common things we hear from home gardeners.
How deep should the tubers be?
If you plant begonias too deep, the stems might struggle to reach the surface, or the tuber might rot before it can sprout. A depth of about half an inch to one inch of soil coverage is plenty. The goal is to protect the tuber from drying out while keeping it close enough to the surface to feel the warmth of the air.
Why aren't my tubers sprouting?
Patience is important with begonias. They are not as fast as some other spring bulbs. It can often take three to four weeks—sometimes longer—for the first green tips to appear. If your room is cool (below 60°F), they will grow much slower. Ensure they are in a warm spot and that the soil is damp but not soaking wet.
Can I grow begonias in full sun?
Most tuberous begonias will struggle in full, intense sun. Their leaves are thin and can burn easily, turning brown and crispy at the edges. For a deeper look at light tolerance, see Are Begonias Shade or Sun Plants? If you have a very sunny spot, you might consider other plants, but for those shady corners of the yard, begonias are the perfect solution.
Do begonias need a lot of space?
While they don't have massive root systems, they do appreciate good air circulation. If you crowd them too closely together, they are more likely to develop powdery mildew, a white dusty fungus on the leaves. Spacing them at least 8 inches apart is a simple way to keep them healthy.
Overwintering Your Tubers
In most parts of the US, begonias will not survive the winter outdoors. However, you don't have to buy new ones every year. You can save the tubers and replant them next spring.
- Stop Watering: In the fall, as the weather cools and the leaves begin to yellow, stop watering the plants.
- Lift the Tubers: After the first light frost kills the top of the plant, carefully dig up the tubers.
- Dry and Clean: Let the tubers dry in a cool, dark place for a few days. Once dry, gently brush off any remaining soil and remove the dried stems.
- Store: Place the tubers in a box of peat moss, sawdust, or a paper bag. Store them in a cool, dry place (between 40°F and 50°F) where they won't freeze.
By following these simple storage steps, you can enjoy the same beautiful flowers year after year.
Conclusion
Planting begonia tubers is a wonderful way to add high-impact color to the shaded areas of your home and garden. By starting them indoors, paying attention to the "hollow side" of the tuber, and keeping the soil moisture balanced, you can grow a professional-looking garden with very little stress.
At Longfield Gardens, we want every gardener to feel confident in their ability to grow beautiful flowers, and our 100% Quality Guarantee is part of that promise. Begonias are particularly rewarding because they offer so much beauty in exchange for just a little bit of care.
- Start your tubers indoors 8-12 weeks before the last frost.
- Always plant with the indented side facing up.
- Keep the soil moist but avoid overwatering the center of the tuber.
- Move them outdoors only when the nights are warm and the frost is gone.
"Gardening is a journey of discovery, and begonias are some of the most reliable partners you can have for a shady yard. With the right start, they will bloom tirelessly from early summer until the first frost of autumn."
We encourage you to try a few different varieties, like Begonia Upright Double Superba Mix - Bulk Offer, this year to see which colors and shapes you like best. For more specific planting tips and to see our current selection of tubers, you can visit the Begonia section on our website.
FAQ
How do I know which side of the begonia tuber is the top?
The top of a begonia tuber is the side with a hollow or "dished" indentation, similar to a small bowl. This is where the growth points (eyes) are located. The bottom of the tuber is usually rounded and smoother. If you see any small pink or white sprouts, those should always face upward.
When is the best time to move my begonias outside?
You should only move begonias outside when the danger of frost has passed and nighttime temperatures are consistently above 60°F. Because begonias are tropical plants, they can be stunted or damaged by cold air and chilly soil. It is often best to wait until late May or early June in many northern climates.
Do I need to cover the begonia tubers with a lot of soil?
No, begonia tubers should be planted very shallowly. They only need about half an inch to one inch of soil covering the top. If you bury them too deep, the sprouts may rot before they reach the surface. A light covering is enough to keep the tuber moist while allowing the stems to emerge easily.
Can I grow tuberous begonias in the ground or only in pots?
You can grow tuberous begonias in both garden beds and containers. They perform exceptionally well in pots and hanging baskets because it is easier to control the drainage and soil quality. If planting in the ground, ensure the soil is loose and rich in organic matter to prevent the tubers from sitting in water.
