Table of Contents
- Introduction
- Understanding the Begonia Tuber
- How Deep to Plant Begonia Tubers
- Timing Your Planting for Success
- Choosing the Right Location
- Spacing Your Begonias
- Step-by-Step Planting Guide
- Caring for Your Begonias After Planting
- Common Varieties to Explore
- Realistic Expectations and Troubleshooting
- Overwintering Your Begonia Tubers
- Summary of Begonia Planting
- FAQ
Introduction
There is a unique kind of magic in watching a shady corner of the garden transform into a lush, color-drenched retreat. Tuberous begonias are the stars of the shade, offering some of the most spectacular, rose-like blooms and vibrant foliage you can find. Whether you are looking to fill a hanging basket with cascading flowers or add a pop of brilliance to a garden border, these plants are a rewarding choice for every skill level.
At Longfield Gardens, we want to make sure your gardening experience is as enjoyable and successful as possible. Many gardeners find begonias a bit mysterious because the tubers look a little unusual compared to a typical flower bulb. However, once you understand a few simple basics about how they grow, you will find they are incredibly easy to manage. For more shade favorites, browse our Spring-Planted Bulbs for Shade.
This guide focuses on the most important step for success: getting the planting depth and orientation just right. We will walk you through the process of starting your tubers indoors and moving them to the garden. By following these simple steps, you can look forward to a full season of stunning, high-impact blooms.
Understanding the Begonia Tuber
Before you can determine how deep to plant begonia tubers, it helps to understand what you are holding. Most begonias found in home gardens grow from tubers, which are thickened underground stems that store energy. They often look like small, brown, hairy discs or shallow bowls. For a fuller overview, see our Tips for Growing Tuberous Begonias.
Unlike a tulip or daffodil bulb that has a clear "pointy" end facing up, a begonia tuber is a bit more subtle. One side of the tuber is slightly indented or cupped, resembling a shallow bowl. This is the top. This concave area is where the "eyes" or growth points are located. These eyes will eventually sprout into the stems and leaves of your plant.
The other side of the tuber is rounded, or convex. This domed side is the bottom, and this is where the root system will primarily develop. Identifying these two sides is the first step toward a successful planting. If you ever feel unsure which side is which, you can simply set the tuber on a warm windowsill for a few days. Once you see tiny pink or white nubs starting to emerge from the indented side, you will know exactly which way is up.
Key Takeaway: Always plant begonia tubers with the hollow, bowl-shaped side facing up. This is where the stems will emerge, while the rounded bottom stays in contact with the soil to grow roots.
How Deep to Plant Begonia Tubers
The question of depth is one of the most common concerns for new begonia growers. Because these tubers are sensitive to moisture and air, getting the depth right is essential for a healthy start. If you want a detailed walkthrough, see our How to Plant Begonia Bulbs for Beautiful Shade Gardens.
The General Rule for Depth
As a general rule, begonia tubers should be planted about 1 inch deep. This means that after you place the tuber in the soil, there should be about a half-inch to a full inch of soil covering the top of the tuber.
Planting at this depth provides enough soil to keep the tuber insulated and moist, but it is shallow enough that the young sprouts can easily reach the surface. If you plant them too deep, the sprouts may struggle to break through the soil, and the tuber could potentially rot before it ever sees the sun. If you plant them too shallowly, the tuber might dry out or sit unevenly as the heavy stems begin to grow.
Planting in Containers vs. the Garden
The environment where you plant your begonias can slightly change how you approach the depth.
- In Pots and Baskets: When planting in containers, you have more control over the environment. You can place the tuber on the soil surface and then cover it with just enough potting mix so it is no longer visible. This usually ends up being about a half-inch of coverage.
- In the Garden Soil: In an outdoor garden bed, the soil temperature and moisture levels fluctuate more. Aim for a full inch of soil over the top of the tuber. This extra bit of "blanket" helps protect the tuber from drying winds or unexpected temperature dips in the early spring.
What to Do Next
- Identify the indented (top) and rounded (bottom) sides of your tubers.
- Prepare a loose, well-draining potting mix or garden soil.
- Create a shallow indentation about 1 inch deep for each tuber.
- Place the tuber in the hole and gently cover it with soil.
- Water lightly to settle the soil, but avoid making it soggy.
Timing Your Planting for Success
Begonias are tropical plants that love warmth and cannot tolerate frost. This makes timing just as important as planting depth. If the soil is too cold or if there is a lingering frost, the tubers will not grow well. If you are ordering from Longfield Gardens, our Shipping Information page explains how timing works by zone.
Starting Indoors
Most gardeners choose to start their begonia tubers indoors about 8 to 12 weeks before the last expected frost date in their area. This "head start" is beneficial because begonias are slow growers in their early stages. By starting them inside in late winter or early spring, you will have established plants with leaves ready to go outside as soon as the weather warms up. This results in flowers much earlier in the summer.
To start them indoors, use small pots or a shallow tray filled with potting soil. Follow the same depth rules: tuck them in so they are covered by about a half-inch of soil. Place the pots in a warm spot, ideally around 70°F, with indirect light.
Moving Outdoors
You should only move your begonias outside once the danger of frost has completely passed and the nighttime temperatures consistently stay above 50°F to 60°F. If you move them out too early, the cold can stunt their growth or damage the tender new leaves. You can use the Hardiness Zone Map to help you plan the right window for your area.
Before moving them to their permanent summer home, it is a good idea to "harden them off." This means placing them outside in a sheltered, shady spot for a few hours a day, gradually increasing their time outdoors over a week. This helps the plants adjust to the wind and brighter light of the outdoors.
Choosing the Right Location
Once you know how deep to plant and when to do it, the next step is finding the perfect spot. Begonias have specific preferences for light and drainage that will help them thrive all summer long. For more inspiration, browse our Summer Flowers for Shade.
Light Requirements
Begonias are famous for their love of shade. In most parts of the country, they do best in filtered light or "dappled" shade, such as the area under a tall tree or on a covered porch. Direct afternoon sun can be too intense and may scorch the leaves or cause the flowers to wilt.
If you live in a cooler, northern climate, your begonias might handle a bit more morning sun. However, in hotter southern regions, they will appreciate deep shade during the heat of the day. A spot that gets four to six hours of indirect light is usually perfect.
Soil and Drainage
The word "drainage" simply refers to how fast water leaves the soil. Begonias have a very important rule: they like to be moist, but never soggy. If the soil stays too wet for too long, the tubers can rot.
- In the Garden: If you notice water puddles in your garden hours after a rain, the drainage is likely poor. You can improve this by mixing in organic matter like compost or peat moss, which helps create air pockets in the soil.
- In Containers: Always use a pot with drainage holes at the bottom. Standard potting soil is usually designed to drain well, but you can always add a bit of perlite if you want to be sure.
Key Takeaway: Match your begonias to a spot with filtered light and soil that lets excess water flow away easily. This "right plant, right place" approach prevents the most common growing challenges.
Spacing Your Begonias
Giving your plants enough elbow room is a quiet winner when it comes to garden success. Proper spacing ensures that each plant gets enough nutrients and, more importantly, enough air circulation. Good airflow helps prevent common issues like powdery mildew or spots on the leaves. For container groupings, our Summer Blooming Bulbs for Containers page is a good place to start.
- Tuberous Begonias: For the large-flowered varieties often grown in pots or borders, space the tubers about 8 to 12 inches apart. This gives the lush foliage room to expand without crowding its neighbors.
- Wax Begonias: These are the smaller bedding plants often sold in flats. Because they are smaller, you can plant them closer together, usually about 6 to 8 inches apart, to create a solid carpet of color.
- Hanging Baskets: In a 12-inch hanging basket, you can typically plant three tubers. This creates a full, cascading look that covers the entire container as the plants mature.
When you are planting, it may seem like there is a lot of empty space between the tubers. Be patient! Within a few months, those small tubers will grow into substantial plants that fill the space beautifully.
Step-by-Step Planting Guide
Ready to get your begonias in the ground or in pots? Follow these simple steps for a stress-free planting day.
For Container Planting
- Select a Pot: Choose a container with drainage holes. A 6-inch pot is perfect for a single tuber, while larger pots can hold more.
- Fill with Soil: Fill the pot about two-thirds full with a high-quality potting mix.
- Position the Tuber: Place the tuber on the soil with the indented side facing up.
- Cover: Add enough soil to cover the top of the tuber by about a half-inch.
- Water: Give it a light drink of water to settle the soil. Avoid soaking it until you see green sprouts appearing.
- Find a Warm Spot: Keep the pot in a room that stays around 70°F.
For Garden Planting
- Wait for Warmth: Ensure the soil is warm and the threat of frost is gone.
- Prepare the Spot: Loosen the soil to a depth of about 6 inches and mix in a little compost.
- Dig the Hole: Dig a shallow hole about 1 to 2 inches deep.
- Plant: Place the tuber in the hole, hollow side up.
- Backfill: Cover the tuber with 1 inch of soil.
- Space: Ensure the next tuber is at least 8 to 12 inches away.
- Water: Water the area gently to help the tuber settle into its new home.
What to Do Next
- Check your pots or garden beds weekly for signs of new growth.
- Keep the soil consistently moist but not saturated.
- Label your varieties so you remember which colors are which.
Caring for Your Begonias After Planting
Once your begonias are tucked into the soil at the right depth, the hardest part is over. Now, your job is to provide the consistent care they need to produce those famous blooms.
Watering Wisely
Watering is the most important part of begonia maintenance. The goal is to keep the soil like a wrung-out sponge: damp but not dripping.
Instead of watering a little bit every day, it is better to water deeply and then wait until the top inch of soil feels dry to the touch before watering again. For begonias in containers, this might mean watering every day during a heatwave, or every few days in cooler weather. In the garden, a deep soak once or twice a week is usually sufficient, depending on the rainfall.
Feeding Your Plants
Begonias are "heavy feeders," meaning they use a lot of energy to produce those big flowers. Once the plants have several sets of leaves and are growing vigorously, you can start using a balanced, water-soluble fertilizer. Following the instructions on the package every two to four weeks will provide the nutrients they need to keep blooming right up until the first frost of autumn.
Deadheading
"Deadheading" is a gardening term that simply means removing faded or spent flowers. When a begonia bloom starts to wilt or turn brown, gently pinch it off at the stem. This keeps the plant looking tidy and encourages it to put its energy into creating new flower buds rather than producing seeds.
Common Varieties to Explore
We offer a wide selection of begonias at Longfield Gardens, each with its own unique personality. Knowing which type you are planting can help you decide where they will look best in your yard.
- Upright Tuberous Begonias: These are the classics. Upright Double Begonias are excellent for garden borders and large patio pots.
- Trailing or Pendula Begonias: Begonia Hanging Golden Balcony is bred for hanging baskets and large planters.
- Scented Begonias: While most begonias don't have a strong fragrance, some specialty varieties offer a delicate, sweet scent that is wonderful near a seating area or entryway.
- Specialty Foliage Begonias: Some begonias, like the Rex types, are grown primarily for their stunning, multi-colored leaves. While they still have small flowers, their foliage is the real showstopper.
Regardless of the variety, the planting depth remains the same. Whether it is a trailing type or an upright type, that 1-inch depth and "hollow side up" rule will serve you well.
Realistic Expectations and Troubleshooting
Gardening is a partnership with nature, and sometimes things don't go exactly as planned. Most begonia issues can be solved with a quick adjustment to their environment. If you want more general help with spring-planted bulbs, see our FAQs - Spring Planted Bulbs.
Slow Starting
Don't be discouraged if your begonias don't sprout immediately. Tubers can be slow to wake up, sometimes taking three to four weeks to show their first green leaves. As long as the tuber feels firm and the soil is warm, they are likely just taking their time.
Yellow Leaves
If you notice the leaves turning yellow, it is often a sign of too much water. Check the soil—if it feels very wet or muddy, let it dry out for a few days. Ensure your pots are draining properly and that you aren't leaving them sitting in a saucer full of water.
Lack of Blooms
If your plant is lush and green but has no flowers, it might need a bit more light. While begonias love shade, they still need indirect light to produce the energy for blooming. Moving a pot to a slightly brighter spot can often trigger a flush of new buds.
Overwintering Your Begonia Tubers
In most parts of the United States, begonias are treated as annuals because they cannot survive the winter outdoors. However, you can easily save your tubers to plant again next year. This is one of the most rewarding parts of growing begonias—watching your collection grow larger and more beautiful each season.
When the leaves begin to yellow in late autumn, or after the first very light frost, stop watering the plants. Let the foliage die back naturally. Once the stems have withered, carefully lift the tubers out of the soil.
Shake off any excess dirt and let them sit in a dry, shaded spot for a few days to "cure." Then, store them in a cool, dry place (like a basement or garage) in a box filled with peat moss or sawdust. Next spring, you can pull them out, follow the same planting depth and care instructions, and enjoy the show all over again.
Summary of Begonia Planting
Growing begonias is an achievable way to bring high-end beauty to your home landscape. By focusing on the simple basics—planting at the right depth, choosing a shady spot, and managing moisture—you can ensure a successful growing season.
- Planting Depth: Aim for 1 inch of soil coverage over the top of the tuber.
- Orientation: Always plant with the hollow/indented side facing up.
- Timing: Start indoors 8-12 weeks before frost or plant outdoors once the soil is warm and nights are above 50°F.
- Watering: Keep soil consistently moist like a wrung-out sponge, but never soggy.
- Location: Choose a spot with dappled shade or indirect light and excellent drainage.
Key Takeaway: Success with begonias starts with the tuber. Getting the depth and orientation right provides the foundation for a season full of incredible, rose-like blooms.
At Longfield Gardens, we believe that every yard has the potential to be a masterpiece. We are here to provide the quality plants and practical advice you need to make your gardening dreams a reality. Whether you are planting your very first begonia or your fiftieth, we wish you a season filled with color and joy.
FAQ
Can I plant begonia tubers directly in the garden?
Yes, you can plant begonia tubers directly in the garden once the soil is warm and all danger of frost has passed. However, because begonias are slow to start, they may not begin blooming until later in the summer. Starting them indoors in pots a few weeks early is the best way to enjoy flowers for a longer period.
Which way is up on a begonia tuber?
The "up" side of a begonia tuber is the side with a shallow, bowl-like indentation. This concave side is where the new stems and leaves will grow. The rounded, smooth side is the bottom and should be placed facing down into the soil.
What happens if I plant my begonia tubers too deep?
If begonia tubers are planted too deep (more than 2 inches), the tender young sprouts may struggle to reach the surface, leading to a weak plant. Additionally, deep planting increases the risk of the tuber rotting due to excess moisture and a lack of oxygen in the soil.
Do I need to soak begonia tubers before planting?
While some gardeners like to soak tubers for an hour or two to "wake them up," it is generally not necessary. As long as you plant them in moist soil and keep them in a warm environment, they will hydrate and begin growing on their own. Avoiding an initial soak can also reduce the risk of rot for beginners.