Table of Contents
- Introduction
- The Short Answer: To Soak or Not to Soak?
- Why Some Gardeners Choose to Soak
- How to Properly Soak Begonia Tubers
- Identifying the Top and Bottom of the Tuber
- Timing Your Planting
- Choosing the Right Soil and Container
- The Proper Planting Depth
- Care During the "Waking Up" Phase
- Transitioning to the Great Outdoors
- Choosing Your Varieties
- Ongoing Summer Care
- What to Expect: A Realistic Timeline
- Saving Your Tubers for Next Year
- Enjoying the Rewards
- Conclusion
- FAQ
Introduction
There is a unique kind of magic in watching a shady corner of the garden transform into a lush, color-filled sanctuary. Tuberous begonias are the stars of these quiet spaces, offering rose-like blossoms and dramatic foliage that thrive where other flowers might struggle. Whether you are tucking them into hanging baskets or lining a woodland path, the anticipation of those first buds is one of the most rewarding parts of the spring season. At Longfield Gardens, we want to help you get the most out of every tuber, ensuring your garden is a source of joy from the first sprout to the final frost.
As you prepare for the growing season, you might wonder about the best way to "wake up" your begonias. A common question for both new and experienced gardeners is whether or not you should soak the tubers before they go into the soil. While this step isn't strictly mandatory, it can be a helpful way to jumpstart the growing process.
This guide will walk you through the benefits of soaking, the best way to do it safely, and the essential steps for planting your begonias to ensure a season full of spectacular blooms. We will cover everything from identifying the right side of the tuber to managing moisture and warmth for the best results. Our goal is to make your gardening experience simple, successful, and entirely enjoyable.
The Short Answer: To Soak or Not to Soak?
The quick answer is that soaking begonia tubers is a helpful option, but it is not a requirement for success. Think of a begonia tuber as a dormant storage unit full of energy. When you introduce moisture and warmth, you are sending a signal to the plant that it is time to start growing.
Soaking can help "plump up" a tuber that has become very dry during winter storage or transit. This extra bit of hydration can sometimes shave a few days off the time it takes for the first "pinkies"—the tiny pink or red growth buds—to appear. However, begonias are also very sensitive to excess moisture. If you choose to soak, it must be done with care to avoid the risk of rot.
If you are a beginner or prefer a hands-off approach, you can skip the soaking step entirely. Simply planting the tubers into moist (but not soggy) potting mix in a warm room will also wake them up effectively. The choice depends on your schedule and how much you want to involve yourself in the early "budding up" phase.
Why Some Gardeners Choose to Soak
The primary reason to soak begonia tubers is to initiate the transition from dormancy to active growth more quickly. During the winter, these tubers are kept in a cool, dry state to prevent them from sprouting too early. By the time spring arrives, the outer skin of the tuber can be quite hard and dry.
A brief soak softens this outer layer and allows water to penetrate the internal tissues. This hydration triggers the metabolic processes inside the tuber. For gardeners in shorter growing zones, every day counts. Starting the tubers indoors and giving them a quick soak can result in a larger, more established plant by the time it is safe to move them outdoors.
Some advanced growers also use this time to apply a very dilute, water-soluble fertilizer or a seaweed-based tonic. This provides a tiny boost of nutrients right at the moment the roots are ready to emerge. While this isn't necessary for beautiful flowers, it is a common practice for those looking to grow exhibition-quality plants.
How to Properly Soak Begonia Tubers
If you decide that soaking is the right move for your garden, follow these simple steps to ensure you do it safely. Remember, the goal is hydration, not drowning.
1. Use Lukewarm Water
Avoid using very cold or very hot water. Lukewarm water is the most "gentle" on the dormant plant tissue. It mimics the natural warming of the soil in spring without shocking the tuber.
2. Keep the Time Brief
You do not need to soak begonias for hours. A period of 15 to 30 minutes is usually more than enough to hydrate the outer layers. Avoid leaving them in water for longer than an hour, as this can deprive the tuber of oxygen and lead to cellular breakdown or rot.
3. Add Optional Nutrients (Carefully)
If you wish to use a fertilizer, make sure it is diluted to at least one-quarter of the strength recommended on the label. The first roots that emerge are incredibly tender and can be easily burned by strong chemicals. A "weak tea" approach is always safer.
4. Drain and Pat Dry
Once the time is up, remove the tubers from the water and let them sit on a paper towel for a few minutes. You want them to be hydrated, but you don't want to trap a pool of water in the "bowl" of the tuber when you place it in the soil.
Key Takeaway: Soaking is an optional 15–30 minute step that can help jumpstart dormant tubers by softening their outer skin and signaling the start of the growing season.
Identifying the Top and Bottom of the Tuber
Before the tubers hit the soil, you must know which way is up. This is one of the most common points of confusion for new gardeners. Planting a tuber upside down won't necessarily kill it, but the plant will have to work much harder to send its sprouts around the sides of the tuber to reach the light.
Begonia tubers are shaped somewhat like a thick coin or a shallow bowl. One side is typically indented or "cupped," while the other side is rounded.
- The Top: The indented or hollow side is the top. This is where the stems and leaves will emerge. If you look closely, you may see tiny, reddish bumps in this hollow area—these are the eyes or "pinkies" that will become the main stems.
- The Bottom: The rounded side is the bottom. This is where the root system will develop. Sometimes you will see the dried remains of last year's roots on this side.
If you find yourself with a tuber that is perfectly flat on both sides and you truly cannot tell which way is up, simply plant it on its side. The plant is smart enough to direct its roots toward the soil and its stems toward the sun.
Timing Your Planting
Tuberous begonias are tropical plants. They love warmth and have absolutely no tolerance for frost. Because they take a while to get going—usually 6 to 8 weeks from planting to the first flower—most people start them indoors in late winter or early spring.
Starting Indoors
The best time to start your begonias indoors is about two months before your area's average last frost date. By starting them inside, you give the plants a head start so they are already blooming or ready to bloom when the weather finally stays warm.
Direct Planting Outdoors
You can plant begonia tubers directly into the garden or outdoor containers, but you must wait until the soil is warm and there is no longer any danger of frost. If you want help matching planting time to your area, see our Shipping Information. In many regions, this isn't until late May or early June. If you wait this long to start, you might not see flowers until late summer. Starting indoors is almost always the better option for maximum enjoyment.
Choosing the Right Soil and Container
Begonias are particular about their "feet." They need a growing medium that stays moist but never stays wet. Drainage is the most important factor in choosing a soil and a pot.
The Potting Mix
Use a high-quality, lightweight potting soil. Look for a mix that contains peat moss, coco coir, or perlite. These ingredients help the soil hold onto just enough moisture while allowing the excess to drain away quickly. Avoid using heavy garden soil in pots, as it will compact and suffocate the roots.
The Container
Whether you are using a decorative ceramic pot, a plastic nursery liner, or a hanging basket, ensure it has plenty of drainage holes. If you have a beautiful pot without holes, use it as a "cachepot"—plant the begonia in a slightly smaller plastic pot with holes, then set that inside the decorative one.
When choosing a pot size, give the tuber a little room to grow. A good rule of thumb is to have about 1 to 2 inches of space between the edge of the tuber and the side of the pot.
Action Plan for Potting:
- Select a container with excellent drainage.
- Fill with a light, airy potting mix.
- Moisten the soil slightly before planting.
- Place the tuber hollow-side up.
The Proper Planting Depth
One of the biggest mistakes gardeners make is burying begonia tubers too deep. If they are buried under inches of heavy soil, the tender new sprouts might rot before they ever reach the surface.
The "Simple Rule" for how deep to plant begonias is to just barely cover them. Place the tuber in the center of your pot and press it gently into the soil. Then, sprinkle just enough potting mix over the top so the tuber is covered by about half an inch to an inch of soil.
If you are planting multiple tubers in a large container or a garden bed, space them about 8 to 12 inches apart. This gives the foliage plenty of room to spread out and ensures good air circulation, which helps prevent powdery mildew and other fungal issues later in the summer.
Care During the "Waking Up" Phase
Once your tubers are in their pots, their needs are very simple: warmth and light.
Temperature Matters
Begonias are most comfortable when the temperature is around 70°F. If your house is cool, you might consider placing the pots on a water-resistant seedling heat mat. This gentle bottom heat is often the "secret" to fast sprouting.
Light Requirements
While the tubers are still underground, they don't need light. However, the moment those first green or red leaves break the surface, they need bright, indirect sunlight. A north or east-facing window is often perfect. Avoid placing them in a south-facing window with harsh, direct midday sun, as this can scorch the tender new growth.
The "Water Sparingly" Rule
This is the most critical stage for watering. Until you see active green growth above the soil, the tuber has no leaves to "breathe out" moisture. If you water too much now, the soil will stay saturated and the tuber will likely rot. Keep the soil barely moist—like a wrung-out sponge. Once the plant has several sets of leaves, you can begin to water more regularly.
Transitioning to the Great Outdoors
Moving your begonias from the controlled environment of your home to the garden is a process called hardening off. This prevents the plants from going into shock due to changes in light, wind, and temperature.
Check the Weather
Do not move begonias outside until nighttime temperatures are consistently above 50°F. Even a light frost will turn the leaves to mush, and cold nights can stall their growth for weeks.
The Hardening Off Process
Start by placing your pots in a shaded, sheltered spot outside for just a few hours during the day. Bring them back inside at night. Gradually increase the amount of time they spend outdoors over the course of a week.
Final Location
Choose a spot that receives morning sun and afternoon shade, or dappled light under a tree. Tuberous begonias are among the best plants for shade, but they do need some light to produce those massive flowers. Protection from strong winds is also important, as their stems can be somewhat brittle.
Choosing Your Varieties
Part of the fun of growing begonias is the incredible variety of flower shapes and growth habits. When you shop with us, you will find options for every corner of your garden.
- Roseform Begonias: These are the "queens" of the garden, featuring huge, double blooms that look remarkably like roses. They are perfect for upright containers and garden beds.
- Pendula (Hanging) Begonias: These varieties have a cascading habit, making them the ideal choice for hanging baskets and window boxes. They produce a profusion of smaller flowers that drape beautifully over the edges.
- Fimbriata Begonias: These unique flowers have fringed, ruffled edges that look like carnations. They add a wonderful texture to any display.
- Non-Stop Begonias: As the name suggests, these are bred to bloom continuously all season long. They are generally more compact and excellent for front-of-the-border planting.
Regardless of the variety, the care remains the same. The choice really comes down to your personal style and where you plan to display them.
Ongoing Summer Care
Once your begonias are established and blooming, they are relatively low-maintenance, but a little extra attention will keep them looking their best until the first frost.
Deadheading
To encourage the plant to keep producing new flowers, remove the old ones as they begin to wilt. This process, called deadheading, prevents the plant from putting energy into seed production. Simply pinch off the flower stem where it meets the main branch.
Feeding
Begonias are "heavy feeders." To support those large, showy blooms, use a balanced liquid fertilizer every two weeks. Follow the instructions on the package, and always water your plants with plain water first before applying fertilizer to avoid burning the roots.
Moisture Management
In the heat of summer, containers and hanging baskets can dry out quickly. Check the soil daily. If the top inch of soil feels dry, it is time to water. Try to water at the base of the plant rather than over the leaves to keep the foliage dry and healthy.
Maintenance Checklist:
- Check soil moisture daily.
- Fertilize every 10–14 days.
- Remove spent blooms regularly.
- Protect from high winds and midday sun.
What to Expect: A Realistic Timeline
Gardening is a lesson in patience, and begonias are no exception. While the soaking step can help, these plants still follow their own internal clock.
- Weeks 1-3: You may see very little happening above the soil. This is when the tuber is busy growing its root system.
- Weeks 4-6: Small sprouts will appear. Growth starts slowly but accelerates as more leaves develop.
- Weeks 8-10: The first flower buds will begin to form.
- Mid-Summer to Frost: The plant should be in full bloom, providing a constant display of color.
The exact timing will always depend on your local weather, the amount of light the plants receive, and how warm you keep them during the early stages. If your plant seems slow, don't worry—as long as the stems are firm and green, it is simply taking its time to build a strong foundation.
Saving Your Tubers 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 replant them year after year, and often, the tubers get larger and more productive with age.
When the weather turns cold in the fall and the leaves start to yellow, stop watering the plants. After the first light frost kills the top growth, dig up the tubers or remove them from their pots. Cut the stems back to about an inch above the tuber.
Let the tubers dry in a cool, protected spot for a few days until any remaining soil can be easily brushed off. Store them in a box of peat moss, vermiculite, or even individual paper bags in a cool, dark place (around 50°F) for the winter. Next spring, you can start the whole process over again, perhaps beginning with that optional 20-minute soak!
Enjoying the Rewards
Tuberous begonias offer some of the most vibrant colors and impressive flower sizes of any shade-loving plant. By taking the time to understand their simple needs—warmth, well-drained soil, and a gentle start—you can ensure your garden is a stunning success. Whether you choose to soak your tubers for that extra head start or prefer the slow and steady approach, the result is the same: a summer filled with breathtaking beauty.
At Longfield Gardens, we believe that gardening should be a rewarding and relaxing part of your life. By focusing on these few essential basics, you can grow begonias with confidence. There is no better feeling than sitting on a porch or patio surrounded by the lush, cascading blooms you nurtured from a simple brown tuber.
"The secret to beautiful begonias isn't found in a magic trick or an internet hack—it's simply about providing the warmth and consistent care they need to thrive."
Conclusion
Deciding whether to soak your begonia tubers is just the first step in a wonderful gardening journey. While it is a great way to rehydrate dry tubers and encourage faster sprouting, your begonias will still grow beautifully without it as long as they have the right soil and plenty of warmth. Focus on the basics: plant them hollow-side up, keep the soil moist but not wet, and wait for the weather to warm up before moving them outside.
If you're ready to add some spectacular color to your shade garden, we invite you to explore our Upright Double Begonias collection. At Longfield Gardens, we stand behind the quality of our plants and want to ensure you have everything you need for a successful season. Our 100% Quality Guarantee is part of that promise.
- Start your tubers indoors 6–8 weeks before the last frost.
- Ensure excellent drainage in all pots and baskets.
- Protect plants from direct midday sun and cold nights.
- Enjoy the repeat blooms all the way until autumn.
FAQ
How long should I soak begonia tubers?
You should only soak begonia tubers for about 15 to 30 minutes. Using lukewarm water is best, as it gently hydrates the tuber without the risk of oxygen deprivation or rot that comes with long-term submersion. Never leave them in water overnight.
Does soaking begonias prevent them from rotting?
Actually, the opposite is true if you aren't careful. While a short soak is safe, over-watering or over-soaking is the most common cause of rot. The key to preventing rot is using well-drained soil and watering very sparingly until you see green sprouts and leaves. For more detail, see our how much water a begonia plant needs guide.
Can I skip the soaking step and still get good results?
Yes, soaking is completely optional. Many gardeners find great success by simply placing the tubers directly into moist potting mix. As long as the room is warm (around 70°F), the tubers will naturally wake up and begin to grow on their own schedule. If you want help matching timing to your area, use the USDA Hardiness Zone Map.
What should I do if my tuber is soft after soaking?
A healthy begonia tuber should feel firm, similar to a potato. If a tuber feels very soft, mushy, or hollow after soaking, it may have already begun to rot and is unlikely to grow. Always start with firm, high-quality tubers for the best chance of success.