Table of Contents
- Introduction
- To Soak or Not to Soak: The Short Answer
- How to Soak Begonia Bulbs Correctly
- When to Start Your Begonia Tubers
- Choosing the Right Containers and Soil
- Planting Technique: Which Way is Up?
- Caring for Sprouting Tubers
- Moving Your Begonias Outdoors
- Summer Care for Maximum Blooms
- Understanding Different Begonia Types
- Troubleshooting Common Issues
- The Longfield Gardens Quality Commitment
- Conclusion
- FAQ
Introduction
There is a unique kind of magic in watching a tuberous begonia unfurl its first rose-like bloom. For many gardeners, these plants are the undisputed stars of the shady corner, offering lush, tropical foliage and vibrant colors that last from early summer until the first frost. Whether you are planting them in elegant hanging baskets or using them to brighten a woodland border, getting off to a strong start is the best way to ensure a spectacular show.
At Longfield Gardens, we want every gardener to feel confident when they bring new life into their yard. Many people wonder if there is a "secret step" to waking up these dormant begonia tubers, specifically asking: do you soak begonia bulbs before planting? This guide will answer that question in detail and walk you through everything you need to know to grow healthy, floriferous begonias. (longfield-gardens.com)
We will cover the benefits and risks of soaking, the best timing for planting, and the simple steps you can take to move your begonias from indoor containers to the outdoor garden. This article is designed for home gardeners who want to maximize their success with tuberous begonias this season. While these plants require a bit of patience at the start, the reward is a summer filled with some of the most beautiful flowers in the gardening world.
To Soak or Not to Soak: The Short Answer
The short answer is that soaking begonia tubers is optional, but it can be a helpful way to jumpstart the growing process. Because begonia tubers are often quite dry and hard when they arrive for spring planting, a brief period of hydration can help "wake them up" from their winter dormancy. This moisture signals to the tuber that it is time to begin pushing out new roots and stems.
However, soaking is not a requirement for success. If your soil is consistently moist and warm, the tubers will naturally hydrate and begin to grow on their own. The primary reason gardeners choose to soak is to shave a few days or even a week off the initial sprouting time. If you live in a region with a short growing season, every day of early growth counts.
It is important to remember that begonias are sensitive to excess moisture. While a quick soak is beneficial, leaving a tuber in water for too long can lead to rot before the plant even has a chance to sprout. The goal is to hydrate the outer layer of the tuber, not to saturate it completely.
Key Takeaway: Soaking is an optional "pro tip" that can speed up sprouting by hydrating dormant tubers. It is helpful but not mandatory, and it must be done carefully to avoid rot.
How to Soak Begonia Bulbs Correctly
If you decide to soak your tubers, doing it correctly is the difference between a head start and a failed plant. You do not need any fancy equipment or special chemicals to get the job done.
The Best Water Temperature
Always use room-temperature water. Avoid using water that is very cold or very hot, as this can shock the dormant tissue of the tuber. Think of the water as a gentle wake-up call; you want it to feel neutral to the touch.
Timing is Everything
The most common mistake gardeners make when soaking any bulb or tuber is leaving it in the water for too long. For begonia tubers, a soak of 1 to 2 hours is plenty. You should never leave them submerged overnight. After two hours, the tuber has typically absorbed all the surface moisture it needs to trigger growth.
The Drying Phase
Once you remove the tubers from the water, let them sit on a paper towel or a clean tray for about an hour before you put them in the soil. This allows the very outer "skin" to dry slightly, which helps prevent fungal issues once they are tucked into the potting mix.
What to Do Next
- Prepare a shallow tray or small pots with a light, well-draining potting mix.
- Place the soaked tubers on the surface of the soil to identify the "up" side.
- Check for "pinkies," which are the tiny pink or white buds that indicate the tuber is waking up.
- Plant immediately after the short drying period to keep the internal hydration high. For a fuller planting walkthrough, see our How to Plant Begonia Tubers. (longfield-gardens.com)
When to Start Your Begonia Tubers
Timing is a much bigger factor in begonia success than soaking. These are tropical plants that love warmth and cannot tolerate even a light frost. Because they take a while to get going—often 6 to 8 weeks from planting to the first flower—most gardeners in the United States choose to start them indoors.
Starting Indoors for Earlier Blooms
For the best results, start your begonia tubers indoors about 8 to 12 weeks before your last expected spring frost. In most regions, this means planting them in containers in March or April. This "head start" allows the plants to develop a strong root system and several inches of leafy growth before they ever touch the outdoor air. By the time the weather is warm enough for them to be outside, they will be ready to begin blooming almost immediately. For a local guide, see our When to Plant Begonias Outdoors article. (longfield-gardens.com)
Planting Directly Outdoors
You can plant begonia tubers directly into the garden or outdoor containers, but you must wait until the soil is warm and all danger of frost has passed. This usually happens in late May or early June. The downside to this method is that your begonias may not begin blooming until late summer. If you want a full season of color, starting them indoors is the way to go.
Shipping and Local Conditions
Our Shipping Information page is designed to help with this timing. We ship your bulbs and tubers based on your USDA hardiness zone so that they arrive at the appropriate time for indoor starting or outdoor planting. Keep an eye on your local weather forecast, as an unusually cold spring might mean waiting an extra week before moving plants to an unheated porch or greenhouse. (longfield-gardens.com)
Choosing the Right Containers and Soil
Begonias are somewhat picky about their "home." Because their tubers are susceptible to rot, the quality of the soil and the drainage of the container are non-negotiable.
The Importance of Drainage
In gardening terms, "drainage" simply refers to how fast water leaves the soil. Begonias need soil that stays moist like a wrung-out sponge but never feels like a puddle. If you are planting in pots, ensure there are plenty of holes in the bottom. If you are planting in the ground, avoid low spots where water collects after a rainstorm.
Creating the Perfect Soil Mix
For indoor starting, a "soilless" potting mix is often best. These mixes usually contain peat moss, perlite, or vermiculite. They are very light and fluffy, which makes it easy for tender new roots to grow.
- Peat Moss: Helps hold onto just enough moisture.
- Perlite: Those little white "lava rocks" that create air pockets so the roots can breathe.
- Potting Soil: Provides a stable base for the plant as it gets larger.
Sizing Your Pots
When starting tubers individually, a 6-inch pot is usually sufficient for one medium-sized tuber. If you are planting multiple tubers in a large decorative container or a Hanging Begonias display, space them about 8 to 12 inches apart. Giving them enough room ensures good air circulation, which keeps the foliage healthy and prevents mildew. (longfield-gardens.com)
Key Takeaway: Use a light, peat-based potting mix and a container with excellent drainage. Avoid heavy garden soil in pots, as it packs down too tightly and can suffocate the roots.
Planting Technique: Which Way is Up?
One of the most frequent questions we hear is how to tell which side of the begonia tuber should face the sky. Unlike a tulip bulb, which has a clear "pointy" end, a begonia tuber can look like a dark, fuzzy potato.
Identifying the Concave Side
Most tuberous begonias have a slightly hollow or "indented" side. This is the top. Think of it like a small bowl or saucer. The sprouts will emerge from the center of this hollow area. The rounded, smooth side is the bottom, where the roots will grow.
What if Both Sides Look the Same?
Sometimes it is hard to tell which side is hollow. If you are unsure, look for "eyes" or "pinkies." These are small, colorful bumps that look like the eyes on a potato. These bumps are the beginning of the stems, so they should always face up. If you still can't tell, you can plant the tuber on its side. The plant is smart enough to send roots down and stems up! If you are curious about a classic picotee form, see Picotee White. (longfield-gardens.com)
Planting Depth
Begonias do not like to be buried deep. In fact, planting them too deep is a common reason they fail to sprout.
- Place the tuber on top of the moist soil mix, hollow side up.
- Press it gently into the soil so it is nestled in, but do not bury it.
- Cover the tuber with just a half-inch to one inch of soil.
- If you are starting them in a very humid environment, some gardeners even leave the very tops of the tubers exposed until they see sprouts, then add a little more soil later.
Caring for Sprouting Tubers
Once your tubers are in the soil, they need a specific environment to begin growing. This phase requires a bit of "watchful waiting."
Heat and Light
Begonias need warmth to sprout. A room temperature of 65°F to 75°F is ideal. Many gardeners find success by placing their starting trays on top of a refrigerator or using a gentle seedling heat mat. You do not need bright light until you see green stems poking through the soil. Once the sprouts appear, move the pots to a bright window with indirect light. Avoid direct, harsh sunlight at this stage, as it can scorch the tender new leaves.
Watering the New Growth
This is the most critical time for moisture management. When the tubers are first planted, water them once to settle the soil. After that, wait until the soil surface feels dry to the touch before watering again. Using a spray bottle to mist the soil surface can be a great way to keep it moist without accidentally over-saturating the tuber. Once the plant has several leaves and is growing vigorously, you can begin watering more deeply. For a more detailed follow-up on growing conditions, see our How to Plant Begonia Tubers. (longfield-gardens.com)
Humidity Boosters
If your home is very dry in the spring, you can loosely cover your pots with plastic wrap or a clear plastic dome. This creates a mini-greenhouse effect that keeps the humidity high. Just be sure to remove the cover for an hour each day to let fresh air circulate, and take it off permanently as soon as the sprouts are an inch tall.
Moving Your Begonias Outdoors
Transitioning plants from the cozy indoors to the unpredictable outdoors is a process called "hardening off." Doing this gradually prevents the plants from going into shock.
The Hardening Off Process
When nighttime temperatures are consistently above 50°F and there is no threat of frost, start by placing your pots in a shaded, sheltered spot outside for two or three hours. Bring them back inside at night. Over the course of a week, gradually increase the amount of time they spend outside and the amount of light they receive. If you're not sure what zone you are in, check the Hardiness Zone Map. (longfield-gardens.com)
Choosing the Final Spot
Begonias are famous for their love of shade, but "shade" can mean many things.
- Dappled Shade: Under a tree where sunlight filters through the leaves. This is perfect.
- Morning Sun: East-facing spots that get gentle sun until 10:00 AM and shade the rest of the day. This is also excellent.
- Deep Shade: Under a porch or in a north-facing corner. Begonias will grow here, but they may produce fewer flowers.
- Avoid Midday Sun: The hot, intense sun between 12:00 PM and 4:00 PM will wilt the flowers and burn the leaves.
Planting in the Ground
If you choose to move your begonias from pots into garden beds, dig a hole that is slightly larger than the root ball. Carefully slide the plant out of its pot, being very gentle with the brittle stems. Place it in the hole at the same depth it was growing in the pot. Fill in with soil and water immediately to help the roots settle into their new home.
Key Takeaway: Patience pays off during the transition. Never rush begonias into cold soil or bright midday sun. A slow introduction to the outdoors leads to much sturdier plants.
Summer Care for Maximum Blooms
Once your begonias are established in their summer home, they are relatively low-maintenance, but a few simple habits will keep them looking their best until autumn.
Watering Wisely
The "simple rule" for watering begonias is to water deeply, then let the top inch of soil dry out. In the heat of summer, containers and hanging baskets may need water every day, while plants in the ground might only need it twice a week. Always try to water the soil at the base of the plant rather than splashing the leaves. Wet foliage in the shade can lead to powdery mildew or other fungal spots.
Feeding Your Begonias
Begonias are "heavy feeders," meaning they need plenty of nutrients to keep producing those large, showy flowers.
- At Planting: We recommend adding a slow-release fertilizer to the soil.
- During the Season: Use a balanced, water-soluble fertilizer every two weeks. Look for a fertilizer where the middle number (phosphorus) is equal to or slightly higher than the first number (nitrogen). This encourages flower production rather than just green leaves.
- Late Season: Stop fertilizing about a month before you expect the first frost. This allows the plant to start slowing down naturally and preparing for dormancy.
Deadheading and Grooming
"Deadheading" is simply the act of removing flowers that have finished blooming and are beginning to wilt. This isn't just about keeping the plant looking tidy; it also prevents the plant from putting energy into producing seeds. When you remove a spent bloom, the plant redirects that energy into creating the next round of flowers. Simply pinch off the faded flower stem where it meets the main branch.
Staking Tall Varieties
Some upright tuberous begonias produce flowers so large and heavy that the stems can begin to lean. If you notice your plants drooping, you can use a small bamboo stake and a piece of soft garden twine to give them extra support. Be careful not to push the stake through the tuber underground; aim for the edge of the pot or a few inches away from the center of the plant.
Understanding Different Begonia Types
When you shop with us, you will notice several different categories of begonias. Knowing which one you have will help you decide where to plant it. For a broader overview, see our All About Begonias. (longfield-gardens.com)
Upright Tuberous Begonias
These are the classics, featuring huge, double blooms that look like roses or camellias. Browse our Upright Double Begonias to see the forms Longfield Gardens offers. (longfield-gardens.com)
Cascading or Trailing Begonias (Pendula)
These varieties are bred to "flow" over the edges of containers. Begonia Hanging Golden Balcony is a strong example of this trailing style. They have slightly smaller but much more numerous flowers. They are the best choice for hanging baskets or window boxes where you want a waterfall of color. (longfield-gardens.com)
Non-Stop Begonias
As the name suggests, non-stop begonias are bred for continuous, prolific blooming. They tend to be a bit more heat-tolerant than the large-flowered types and are excellent for mass plantings in semi-shaded flower beds. (longfield-gardens.com)
Multiflora Begonias
These plants are more compact and covered in a carpet of smaller blooms. They are very sturdy and hold up well to wind and rain, making them a great "all-purpose" shade plant.
Troubleshooting Common Issues
Even with the best care, you might run into a few hurdles. Most begonia problems are easy to fix once you know what to look for.
Slow Sprouting
If it has been four weeks and you see no green, check the temperature. If the room is below 60°F, the tubers might still be "sleeping." Move them to a warmer spot. Also, gently check the soil moisture; it should be damp, not wet. If you dig one up and it feels firm, it is fine—just give it more time.
Leggy Growth
If your stems are very long and thin with few leaves, the plant is likely stretching for more light. Move it to a brighter location, ensuring it still avoids direct, hot sun.
Dropping Buds
If your plant is growing well but the flower buds fall off before they open, it is usually a sign of stress. This can be caused by soil that is too dry, or by extreme heat. Increase your watering frequency during heatwaves and ensure the plant is well-shaded during the hottest part of the day.
Powdery Mildew
This looks like a dusting of white flour on the leaves. It usually happens when the air is still and humid. To prevent it, make sure your plants aren't crowded together. Improving the air circulation around the plants is usually the best "fix."
The Longfield Gardens Quality Commitment
We take great pride in the quality of the plants we provide. Our tuberous begonias are sourced from trusted growers, including the world-renowned bulb regions of Holland. We maintain a trial garden where we evaluate varieties for their performance, ensuring that what you plant in your garden is true to variety and ready to thrive.
We stand behind our products with a 100% quality guarantee. We promise that your items will arrive in prime condition and be true to the variety you ordered. If you notice any damage or quality issues upon delivery, please contact our customer service team promptly. We want you to be successful, and if a plant fails to perform during its first growing season, we are here to help with a replacement, store credit, or refund depending on the situation. (longfield-gardens.com)
Conclusion
Soaking your begonia tubers is a simple, effective way to help these shade-loving beauties wake up and get growing. While it is an optional step, taking two hours to hydrate your tubers can lead to a faster start and a longer season of incredible blooms. By focusing on the basics—warmth, excellent drainage, and shallow planting—you are well on your way to a stunning display.
Remember these key steps for begonia success:
- Start tubers indoors 8-12 weeks before the last frost.
- Plant with the hollow side up, just below the soil surface.
- Provide bright, indirect light and consistent, moderate moisture.
- Feed regularly with a balanced fertilizer to keep the blooms coming.
Gardening is a journey of patience and reward. The time you spend caring for these tubers in the spring will pay off tenfold when your garden is filled with vibrant, rose-like flowers all summer long.
"Tuberous begonias are the gems of the shade garden. With a little warmth at the start and a cool, shaded spot in the summer, they provide a level of color and elegance that few other plants can match."
If you are ready to start your shade garden, we invite you to explore our selection of premium begonia tubers. We ship directly to your door at the perfect time for planting, so you can focus on the joy of growing. (longfield-gardens.com)
FAQ
Is it too late to soak my begonia tubers if I already planted them?
Yes, once the tubers are in the soil, there is no need to dig them up to soak them. Simply keep the soil consistently moist (but not soggy) and ensure the room is warm (above 65°F). The tubers will naturally hydrate from the surrounding soil and begin to grow on their own.
Can I use a liquid fertilizer in the soaking water?
You can use a very weak, highly diluted liquid fertilizer in the soaking water, but it is generally not necessary. The tuber already contains the energy needed to send out its first sprouts. It is much more effective to begin a regular feeding schedule once the plant has established a few sets of leaves.
Should I soak begonias that I’ve stored from last year?
Yes, soaking is particularly helpful for overwintered tubers. Tubers that have been in storage for several months can become quite dry. A 1-2 hour soak can help rehydrate the tissue and "signal" to the tuber that the dormant period is over and it is time to begin the new growing season.
What happens if I soak my begonia bulbs for too long?
If you soak begonia tubers for more than a few hours, or especially overnight, you risk "drowning" the tissue. Tubers need oxygen just like roots do. Excessive soaking can cause the tuber to soften and rot from the inside out. If you accidentally leave them in too long, let them dry out completely on a tray before planting and hope for the best, but it is always better to stick to the 2-hour limit.