Table of Contents
- Introduction
- Understanding Your Begonia Tubers
- How Deep to Plant Begonia Tubers
- Why Planting Depth Matters
- Which Side Is Up?
- Choosing the Right Soil and Drainage
- The Best Spacing for Begonias
- Timing Your Planting
- Caring for Newly Planted Tubers
- Transitioning Outdoors
- Light and Temperature Requirements
- Realistic Expectations for Growth
- Maintenance for Maximum Blooms
- Lifting and Storing for Next Year
- Conclusion
- FAQ
Introduction
There is nothing quite like the sight of a tuberous begonia in full bloom. These plants are the stars of the shade garden, offering oversized, rose-like blossoms in colors that seem to glow against their lush, dark foliage. Whether you are looking to brighten up a covered porch with hanging baskets or add a splash of color to a quiet garden corner, begonias are a rewarding and accessible choice. At Longfield Gardens, we want to help you get the very best results from your bulbs and tubers by starting with the fundamentals. If you prefer upright growers, our Upright Double Begonias collection is a good place to start.
The key to a healthy, floriferous begonia often comes down to the very first step: how you put the tuber into the soil. Getting the planting depth and orientation right ensures your plant has a sturdy foundation and plenty of energy to grow. In this guide, we will focus specifically on how deep to plant begonia tubers and the simple steps you can take to ensure they thrive all season long. Proper planting is the first step toward a summer filled with spectacular, cascading color.
Understanding Your Begonia Tubers
Before we dig into the soil, it helps to understand what you are holding in your hand. A begonia tuber is a thickened underground stem that stores energy for the plant. It looks a bit like a small, brown, lumpy potato or a thick wooden coin. Unlike a pointed tulip or daffodil bulb, a begonia tuber has a very distinct shape that tells you exactly how it wants to grow. For a broader overview, see our All About Begonias.
One side of the tuber is usually rounded, while the other side has a shallow, bowl-like indentation. This "hollow" side is the top. This is where the eyes, or growth points, are located. You might even see tiny pink or red buds already starting to peek out from that indentation. Knowing which side is the top is just as important as knowing how deep to plant begonia tubers, as it determines the direction the stems will grow.
How Deep to Plant Begonia Tubers
When it comes to planting depth, begonias prefer to stay relatively close to the surface. If you want a step-by-step refresher, see our How Do You Plant Begonia Tubers? guide.
The general rule for how deep to plant begonia tubers is to cover them with just about 1 inch of soil. Whether you are starting them in a decorative container or a garden bed, this shallow depth allows the warmth of the spring sun to reach the tuber, which encourages faster sprouting.
Planting in Containers and Pots
If you are planting your begonias in pots or window boxes, you have a bit more control over the environment. For container gardening, we recommend filling your pot with a high-quality potting mix until it is about 2 inches from the rim. Place the tuber on the surface with the hollow side facing up, then cover it with 1 inch of soil. For cascading color in baskets, browse our Hanging Begonias collection.
This leaves about an inch of space at the top of the pot, which is very helpful when it comes time to water. It prevents the water and soil from washing over the edges. Because pots warm up faster than the ground, this 1-inch depth is the perfect "sweet spot" to get those first leaves appearing quickly.
Planting in Garden Beds
If you are planting directly into your landscape, the depth remains the same: 1 inch. However, you want to make sure the soil is loose and well-worked. A classic upright choice is Begonia Upright Double Roseform Pink.
Dig a shallow hole, place the tuber inside, and gently crumble soil over the top. Avoid packing the soil down with your hands or feet; a light pat is all it takes. This keeps the soil aerated, which means there is plenty of oxygen for the developing roots.
Key Takeaway: Always plant begonia tubers with the hollow side facing up, covered by exactly 1 inch of loose, well-draining soil.
Why Planting Depth Matters
You might wonder why such a small measurement makes a difference. In gardening, depth often dictates the balance between protection and accessibility.
If you plant a begonia tuber too deep—say, 3 or 4 inches down—the young stems have a long way to travel before they reach the light. This uses up a lot of the tuber's stored energy. By the time the leaves emerge, the plant may be weaker and more susceptible to pests. Furthermore, deeper soil stays wetter and cooler for longer. Since begonias are tropical plants, sitting in cold, wet soil can cause the tuber to soften and rot.
On the other hand, planting too shallow (leaving the top of the tuber exposed) can cause the tuber to dry out. The top of the tuber needs that 1-inch layer of soil to act as an insulator, keeping the moisture levels consistent so the growth buds don't shrivel in the wind or sun.
Which Side Is Up?
Identifying the top of the tuber is the most important part of the planting process. If a tuber is planted upside down, it will try its best to grow, but the stems will have to curve all the way around the tuber to reach the surface. This creates a stressed plant and a very late start to the blooming season.
Look for these three signs to identify the top:
- The Indentation: The top is almost always concave, like a shallow bowl or saucer.
- The Buds: Look for small, colorful "pips" or buds inside that hollow area. These are the future stems.
- The Roots: The rounded underside may have hairy, dried remnants of last year’s roots.
If you ever find a tuber that is perfectly flat on both sides and you truly cannot tell which side is up, the safest bet is to plant it on its edge. The plant will naturally direct its stems upward and its roots downward from that position.
Choosing the Right Soil and Drainage
Knowing how deep to plant begonia tubers won't help much if the soil isn't right. "Drainage" is a word gardeners use often, and it simply refers to how fast water leaves the soil. Begonias absolutely insist on good drainage. They like to stay moist, but they never want to sit in "wet feet" or soggy mud.
For the best results, use a soil that is rich in organic matter but light enough to let excess water flow away. In garden beds, you can improve drainage by mixing in some compost or finely ground bark. This creates tiny air pockets in the soil that prevent water from pooling around the tuber.
In containers, always ensure there are drainage holes at the bottom. If you have a beautiful decorative pot that doesn't have a hole, it is best to plant the begonia in a simple plastic "nursery" pot with holes and then set that pot inside the decorative one.
The Best Spacing for Begonias
While depth is our main focus, spacing is its close cousin. Giving your begonias enough room to breathe is essential for preventing mold and mildew on the leaves later in the summer.
- In the Garden: Space tubers 8 to 12 inches apart. This allows for plenty of air circulation and gives the foliage room to spread out without crowding its neighbors.
- In Containers: You can plant them a bit closer for a "full" look. For a standard 12-inch hanging basket, 2 to 3 tubers are usually plenty. For a smaller 8-inch pot, one single tuber is usually the best choice. If you like to plant in quantity, the Begonia Upright Double Superba Mix - Bulk Offer gives you plenty of color for bigger containers.
Timing Your Planting
Begonias are very sensitive to the cold. They are tropical in origin, which means they do not like frost or even chilly nights. In most parts of the US, it is best to wait until the soil is warm and the danger of frost has completely passed before planting them outdoors.
If you live in a northern climate with a short growing season, we highly recommend "starting" your tubers indoors about 8 to 12 weeks before the last expected frost. This gives the plants a head start so you can enjoy blooms much earlier in the summer. If you are unsure of your local climate, the Hardiness Zone Map is a helpful place to begin.
When you start them indoors, follow the same rules for how deep to plant begonia tubers. Place them in a warm spot with indirect light. Once the weather outside is consistently warm (nights should be above 50°F), you can move your pots outside or transplant the sprouted begonias into your garden beds.
What to Do Next: Planting Your Tubers
- Check your tubers for the hollow "top" side.
- Select a pot with drainage holes or a shady garden spot.
- Fill with loose, high-quality potting soil or amended garden soil.
- Place the tuber and cover with 1 inch of soil.
- Water lightly to settle the soil, but do not soak it.
Caring for Newly Planted Tubers
Once your begonias are tucked in at the correct depth, they need a little patience. Begonias are not the fastest starters in the bulb world. It can take several weeks for the first green sprouts to appear above the soil.
During this waiting period, be very careful with the watering can. The tuber does not have a root system yet, so it cannot "drink" much water. If the soil is kept too wet during this stage, the tuber may rot. Keep the soil just barely moist—like a wrung-out sponge. Once you see green leaves poking through the 1 inch of soil, you can begin to water more regularly. For a tidy, container-friendly option, Begonia Upright Double Picotee White is a good example.
As the plant grows, you will notice that begonias have fairly succulent, brittle stems. Because they are planted shallowly, tall upright varieties (like the Roseform or Ruffled types) might benefit from a small bamboo stake once they reach 6 to 10 inches in height. This provides extra support during summer wind or rain.
Transitioning Outdoors
If you started your tubers indoors at that 1-inch depth, moving them to the garden requires a bit of care. If you need help planning shipment timing, our Shipping Information page explains how Longfield schedules orders by zone. This process is called "hardening off." Even though they are at the right depth, the leaves are used to the still, protected air of your home.
Start by placing the pots in a sheltered, shady spot outside for just a few hours a day. Gradually increase the time over a week. This strengthens the plant's tissues. When you are ready to plant them in the ground, ensure the top of the root ball is level with the surrounding soil. Do not bury the stems deeper than they were in the pot, as this can lead to stem rot.
Light and Temperature Requirements
Begonias are famous for their love of shade, but "shade" can mean many things. Most tuberous begonias do best in "filtered light" or "dappled shade." This is the kind of light you find under a tall tree where the sun peeks through the leaves. For more ideas on making a dim spot shine, see Design Tips for Shady Gardens.
In cooler northern climates, begonias can often handle a bit of morning sun as long as they are protected from the harsh, direct rays of the afternoon. In the South, where the sun is much stronger, deep shade or northern exposure is usually best. If the leaves start to look scorched or brown at the edges, it is usually a sign that the plant is getting too much direct sun.
Regarding temperature, begonias are at their happiest when the air is between 60°F and 80°F. If a heatwave hits, your begonias might stop blooming temporarily. Don't worry—this is just the plant's way of conserving energy. Keep them watered, and once the temperatures drop, they will start producing flowers again.
Realistic Expectations for Growth
Gardening is a partnership with nature, and weather always plays a role. While we can provide the best starting conditions by planting at the 1-inch depth, the exact timing of your first bloom will depend on your local climate.
In a warm, humid spring, your begonias might take off like rockets. In a cool, damp spring, they may sit quietly for a month before showing any signs of life. This is perfectly normal. As long as the tuber is firm and not soggy, it is simply waiting for the right "signal" from the environment to start growing. Once they start, they will continue to bloom non-stop until the first frost of autumn.
Key Takeaway: Patience is key with begonias. Once the weather warms up and the roots establish, these plants will provide continuous color for months.
Maintenance for Maximum Blooms
To keep your begonias looking their best throughout the summer, a little bit of grooming goes a long way.
- Deadheading: This is the practice of removing faded flowers. When a bloom starts to wilt, pinch it off at the base of its small stem. This prevents the plant from trying to make seeds and encourages it to put all its energy into making new flowers.
- Fertilizing: Begonias are hungry plants. Once they have several sets of leaves, you can use a balanced, water-soluble fertilizer every two weeks. This provides the nutrients they need to produce those massive, showy blossoms.
- Cleaning: Pick up any fallen petals or leaves that land on the soil. This keeps the area clean and reduces the chance of fungus developing in the shade.
Lifting and Storing for Next Year
One of the best things about tuberous begonias is that they are not a "one and done" plant. You can save the tubers and plant them again next year. Because you planted them just 1 inch deep, they are very easy to lift out of the soil in the fall.
When the leaves begin to turn yellow in late autumn or after the first light frost, stop watering. Let the stems die back naturally. Carefully lift the tubers out of the ground or pot. Let them dry in a cool, protected spot for a few days until the stems fall off easily.
Store the clean, dry tubers in a box of peat moss or sawdust in a cool (but frost-free) place like a basement or closet. Next spring, you can pull them out and start the process all over again. Many gardeners keep the same begonia tubers for many years, and the tubers often get larger and more productive with age.
Conclusion
Planting begonia tubers is one of the simplest ways to bring high-impact color to the shaded parts of your yard. By remembering the "1-inch rule" for depth and ensuring the hollow side faces up, you have already solved the most common challenges gardeners face with these plants. At Longfield Gardens, we believe that focusing on these small, practical details makes gardening more enjoyable and successful for everyone. For added peace of mind, see our 100% Quality Guarantee.
- Plant 1 inch deep in loose, well-draining soil.
- Orient the tuber with the hollow, bowl-shaped side facing the sky.
- Start indoors for an earlier summer show if you live in a cold climate.
- Wait for warm weather before moving your plants into the garden.
The reward for this small amount of effort is a spectacular display of flowers that will last from midsummer right up until the first frost. We invite you to explore the many beautiful varieties available and start your own shade garden masterpiece this season.
"A little bit of attention to planting depth pays off in a summer full of big, beautiful blooms."
FAQ
Which side of the begonia tuber should face up when planting?
The side with the hollow, bowl-shaped indentation should always face up. This is where the new stems and leaves will emerge. If you see tiny pink buds, those are the growth points and they belong on the top.
Can I plant begonia tubers directly in the ground?
Yes, you can plant them directly in the ground once the soil has warmed and all danger of frost has passed. However, in many regions, starting them indoors in pots 8 to 12 weeks early is preferred to ensure a longer blooming season.
What happens if I plant my begonia tubers too deep?
If planted much deeper than 1 inch, the tuber may struggle to send its stems to the surface, leading to weak plants. Deep planting also increases the risk of the tuber rotting because the soil stays cooler and wetter further down.
How long does it take for begonia tubers to sprout after planting?
Begonias are relatively slow to start and can take 2 to 4 weeks to show their first sprouts. The timing depends heavily on the temperature; they will sprout much faster in a warm environment (around 70°F) than in a cool one.