Table of Contents
- Introduction
- Identifying the Top and Bottom of a Begonia Tuber
- Why Planting Direction Matters
- When to Start Your Begonia Tubers
- Preparing the Soil and Containers
- Step-by-Step Planting Guide
- Light and Water Requirements
- Transitioning Begonias to the Outdoors
- Choosing the Best Begonia Varieties
- Simple Care for Constant Blooms
- What to Do at the End of the Season
- Conclusion
- FAQ
Introduction
Tuberous begonias are some of the most rewarding plants you can add to your shade garden. For a look at our current begonia bulbs, Longfield Gardens offers a wide selection for shade containers and borders. They produce stunning, rose-like flowers in a vibrant range of colors that brighten up even the quietest corners of your yard. At Longfield Gardens, we love how these plants transform hanging baskets, window boxes, and garden borders into lush, floral displays.
Starting begonias from tubers is a simple process that feels like a fun science project. You get to watch a dormant, earthy-looking bulb wake up and turn into a magnificent plant. This guide is for any gardener who wants to feel confident about getting their begonias into the ground or a pot.
We will cover exactly how to identify the top of the tuber and the best steps for planting and care. Getting the orientation right is the very first step toward a season full of beautiful blooms.
Identifying the Top and Bottom of a Begonia Tuber
When you first hold a begonia tuber, it might look a little unusual. It is often brown, slightly hairy, and shaped somewhat like a thick potato or a woody disc. Unlike a tulip or a daffodil, which has a clear "pointy end" that goes up, begonias have a different shape.
The Dished Side (Top)
The most important thing to look for is the "bowl" or the "cup." One side of the begonia tuber is slightly hollow or indented. This is the concave side. This "bowl" side should always face up toward the sky. Most of the plant’s growth points, often called "eyes," are located inside this cupped area.
The Domed Side (Bottom)
The opposite side of the tuber is rounded or domed. This is the convex side. This smooth, rounded part should rest on the soil surface or be tucked into the soil. As the plant begins to grow, fine roots will emerge from this domed area and the sides of the tuber to anchor it and draw in moisture.
Looking for "Eyes" or Sprouts
If you look closely at the center of the indented bowl, you might see small, pinkish or reddish nubs. These are the sprouts. They look similar to the "eyes" on a potato. If your tuber has already started to wake up, these sprouts make it very easy to tell which way is up. If you do not see any sprouts yet, do not worry. They will appear once the tuber is exposed to warmth and a bit of moisture.
Key Takeaway: Always plant begonia tubers with the hollow, bowl-shaped side facing up. This ensures the sprouts can reach the light easily and the roots can grow downward.
Why Planting Direction Matters
It might seem like a small detail, but the orientation of the tuber is vital for the health of the plant. Plants are naturally programmed to grow toward the light, but they have a much easier time if they are started in the correct position.
If a tuber is planted upside down, the sprouts have to grow around the body of the tuber to reach the surface. This uses up a significant amount of the tuber's stored energy. It can lead to a weaker plant and a delayed blooming season. In some cases, the sprouts might not make it to the surface at all, especially if the soil is heavy or the tuber is planted too deep.
By placing the "bowl" side up, you are giving those delicate sprouts the shortest and safest path to the air and sunshine. This allows the plant to focus its energy on developing strong leaves and those iconic, showy flowers rather than struggling to find its way out of the dirt.
When to Start Your Begonia Tubers
Tuberous begonias are tropical plants that love warmth. They are very sensitive to cold temperatures and frost. Because they take about 12 to 15 weeks to go from a dormant tuber to a flowering plant, many gardeners choose to give them a head start indoors. For more timing details, see our guide on when to plant begonias.
Starting Indoors
You can start your tubers indoors about 8 to 12 weeks before the last expected frost in your area. This usually means planting them in late winter or early spring. Starting them early ensures you get flowers in early summer rather than waiting until the end of the season.
Planting Directly Outdoors
If you live in a warm climate or prefer to wait, you can plant them directly in the garden. However, you must wait until the soil has warmed up and the danger of frost is completely gone. Nighttime temperatures should consistently stay above 50°F before begonias are moved or planted outside.
What to Do Next: Timing Checklist
- Check your local Hardiness Zone Map to determine your 8–12 week window.
- Gather your pots and potting soil in late winter.
- Keep your tubers in a cool, dry place until you are ready to start them.
- Make sure you have a warm, bright spot indoors for the initial growth phase.
- Review our Shipping Information page if you are ordering from Longfield Gardens.
Preparing the Soil and Containers
Begonias are not very picky, but they do have one firm requirement: excellent drainage. Because the tubers are fleshy and store a lot of water, they can rot if they sit in soggy, waterlogged soil.
Choosing the Right Soil
Whether you are planting in the ground or in a pot, use a high-quality, well-draining soil mix. For containers, a standard peat-based potting soil works well. You can even mix in a little bit of perlite or vermiculite to help keep the soil light and airy. If you are planting in the garden, you can improve heavy clay soil by adding compost or peat moss.
Selecting a Container
If you are starting one tuber, a 6-inch pot is a great size. If you want to plant multiple tubers together for a fuller look, choose a larger pot or Begonia Non Stop Mix - Bulk Offer for a fuller display.
- 6-inch pot: 1 tuber
- 8-to-10-inch pot: 2 tubers
- 12-inch pot: 3 tubers
Make sure every container has drainage holes at the bottom. This allows excess water to escape, keeping the tuber healthy and firm.
Step-by-Step Planting Guide
Once you have identified the top of your tuber and prepared your soil, you are ready to plant. We recommend a simple process that focuses on shallow planting to prevent rot.
Step 1: Fill Your Pot
Fill your container about two-thirds full with moist (but not dripping wet) potting soil. Do not pack the soil down too tightly; you want it to remain loose for the new roots.
Step 2: Position the Tuber
Place the tuber on the surface of the soil with the hollow "bowl" side facing up. Press it gently into the soil so it makes good contact, but do not bury it deep.
Step 3: Cover Lightly
Cover the tuber with about half an inch to one inch of soil. Some gardeners prefer to leave the very top of the tuber slightly exposed until they see sprouts, which is also a safe way to start them indoors. If you are planting directly in the garden, a full inch of soil coverage is best to protect the tuber from drying out.
Step 4: Water Gently
Water the soil just enough to settle it around the tuber. Avoid pouring water directly into the hollow "cup" of the tuber, as standing water in that center area can encourage rot. It is better to water the soil around the edges of the tuber.
Step 5: Provide Warmth
Place your pots in a warm spot. Begonia tubers wake up best when temperatures are around 70°F. They do not need much light until the first leaves appear, but warmth is essential for breaking dormancy.
Key Takeaway: Plant begonias shallowly—no more than an inch deep. Shallow planting prevents moisture from trapped in the tuber's "bowl," which helps prevent rot.
Light and Water Requirements
Begonias are famous for being "shade plants," but they still need a certain amount of light to produce their best flowers. Understanding the balance between light and water is the key to a healthy plant.
Sunlight Needs
In most parts of the country, begonias thrive in "filtered shade" or "dappled sunlight." This means they love being under a tree or on a porch where they get bright light but are protected from the harsh, direct midday sun.
- Morning Sun: A little bit of gentle morning sun is often helpful.
- Afternoon Shade: Hot afternoon sun can scorch the leaves and cause the flowers to wilt.
- Deep Shade: If they are in total shade, the plants may become "leggy" (tall and thin) and produce fewer flowers.
Watering Rules
Watering begonias correctly is more about consistency than quantity. We recommend the "deep, then dry" method.
- Check the soil: Stick your finger an inch into the soil. If it feels dry, it is time to water.
- Water the base: Always try to water the soil, not the leaves. Wet leaves can lead to mildew or spotting.
- Drainage is key: Ensure that any saucers under your pots are emptied after watering. Begonias do not like to have "cold feet" or sit in standing water.
During the hottest parts of the summer, you may need to water your containers every day. In the cooler spring months, once or twice a week is usually enough.
Transitioning Begonias to the Outdoors
If you started your begonias indoors, you cannot move them straight into the garden the moment the sun comes out. They need a transition period to get used to the wind, sun, and temperature changes. This process is called "hardening off."
Step 1: Monitor the Temperature
Wait until the threat of frost has completely passed. Check your local weather forecast for overnight lows. If the temperature is predicted to drop below 50°F, keep your begonias inside for another night.
Step 2: Gradual Exposure
Start by placing your pots in a shaded, protected spot outside for just a few hours during the day. Bring them back inside at night. Over the course of 7 to 10 days, gradually increase the amount of time they spend outside and the amount of light they receive.
Step 3: Final Placement
Once the plants are acclimated, you can transplant them into your garden beds or move their pots to their final summer home. At Longfield Gardens, we have found that begonias are quite happy to stay in pots all season, but they also look beautiful when tucked into the front of a shady border. For more placement ideas, see Where Do I Plant Begonias?.
Choosing the Best Begonia Varieties
There are many different types of tuberous begonias, and choosing the right one depends on where you want to plant it. Most varieties fall into two main categories: upright and trailing.
Upright Begonias
These plants grow tall and sturdy, usually reaching 12 to 18 inches in height. They are perfect for garden beds, window boxes, or the center of a large planter.
- Dinnerplate Begonias: These are known for their massive, ruffled blooms that can be as large as a saucer.
- Fimbriata Begonias: These have unique, fringed petals that look similar to carnations.
- Upright Double Begonias: These produce perfectly symmetrical blooms that look exactly like giant roses.
Trailing (Pendula) Begonias
As the name suggests, these varieties have stems that cascade downward. They are the absolute best choice for hanging baskets and the edges of balcony boxes.
- Begonia Upright Double Roseform Pink: These produce a profusion of smaller flowers that drape beautifully over the sides of a container.
- Hanging Begonias: Some trailing varieties are even bred for a light, sweet fragrance, which is a wonderful surprise in a shade plant.
Regardless of the variety you choose, the planting method remains the same. Whether it is an upright "Dinnerplate" or a trailing "Cascading" type, that hollow side always goes up.
Simple Care for Constant Blooms
One of the best things about begonias is that they are relatively low-maintenance once they are established. You can keep them looking their best with just a few simple tasks.
Deadheading
"Deadheading" is the process of removing flowers that have finished blooming. When a flower starts to wilt or turn brown, simply snip it off at the stem. This keeps the plant looking tidy and encourages it to put its energy into creating new buds.
Fertilizing
Begonias are "heavy feeders," meaning they use a lot of nutrients to produce those big, showy flowers. For a deeper dive, see What is the Best Plant Food for Begonias?. You can use a balanced, water-soluble fertilizer every two to three weeks during the growing season. Follow the instructions on the label to ensure you are giving them the right amount. This extra boost of nutrients will keep the foliage green and the blooms coming all the way until the first frost.
Watching for Pests
Begonias are generally very healthy, but in humid weather, they can sometimes develop powdery mildew (a white, dusty-looking coating on the leaves). To prevent this, make sure there is good air circulation around your plants and avoid getting the leaves wet when you water.
What to Do Next: Summer Maintenance
- Remove faded flowers once a week.
- Fertilize every 14–21 days with a balanced liquid fertilizer.
- Check soil moisture daily during heatwaves.
- Ensure there is space between pots for airflow.
What to Do at the End of the Season
As the weather cools down in the fall, your begonias will naturally begin to slow down. Because they are tropical, they will not survive a freeze. However, you can save the tubers to plant again next year!
When the leaves begin to turn yellow or the first light frost hits, stop watering the plant. Let the foliage die back naturally. Once the stems are dry, you can lift the tubers out of the soil. Shake off the excess dirt and let them dry in a cool, protected spot for a few days.
Store the dry tubers in a cardboard box filled with peat moss or sawdust in a cool (but not freezing) basement or closet. In the spring, you can pull them out and start the whole process over again. A single begonia tuber can provide beauty for many years if it is cared for during the winter.
Conclusion
Planting begonia tubers is a simple and joyful way to bring color to the shady parts of your garden. By remembering to plant the "bowl" side up and the "dome" side down, you give your plants the best possible start. Whether you choose the massive blooms of a Dinnerplate variety or the elegant drape of a trailing begonia, these plants are sure to become a highlight of your summer landscape.
Our team at Longfield Gardens is dedicated to helping you succeed. We ship our tubers from our facility in Lakewood, New Jersey, and we stand behind our 100% quality guarantee. We want your items to arrive in prime condition and be true to their variety so you can garden with confidence.
Key Takeaway: Successful begonia gardening starts with the right orientation and shallow planting. With a little warmth, consistent water, and filtered light, your tubers will reward you with spectacular flowers all season long.
We hope you feel ready to get your garden started. For more specific variety information or to see our current selection, feel free to explore our planning guides and articles. Happy planting!
FAQ
What happens if I plant my begonia tuber upside down?
If a tuber is planted upside down, the sprouts will have to grow around the tuber to find the light. This often results in a very late start to the blooming season, and the plant may be significantly weaker. In some cases, the sprouts may rot before they ever reach the soil surface.
Do I need to soak begonia tubers before planting?
You do not need to soak begonia tubers. In fact, soaking them can sometimes lead to rot if the water gets trapped in the hollow part of the tuber. It is much better to plant them in moist potting soil and let them naturally absorb the moisture they need to wake up.
How deep should I plant the tubers in a garden bed?
In a garden bed, you should plant the tubers about 1 inch deep. This provides enough soil cover to keep the tuber from drying out while still being shallow enough for the sprouts to reach the surface quickly. If you are starting them in pots indoors, you can plant them even shallower, just barely covering the top with a half-inch of soil.
Why is my begonia tuber not sprouting yet?
Begonia tubers can be slow to wake up, sometimes taking 4 to 6 weeks to show their first leaves. The most common reason for a delay is a lack of warmth. Make sure your pots are in a spot that is at least 70°F. If your house is cool, placing the pots on top of a refrigerator or near a warm (but not hot) vent can help "jumpstart" the growth.