Table of Contents
- Introduction
- Choosing the Right Tuberous Begonia for Your Space
- Finding the Perfect Outdoor Location
- Timing Your Planting for Success
- Step-by-Step Guide to Planting Tuberous Begonias
- Caring for Your Begonias Throughout the Summer
- Understanding the "Male and Female" Flowers
- Moving Begonias Indoors for the Winter
- Creating Beautiful Combinations
- Summary of Success for Growing Tuberous Begonias Outdoors
- FAQ
Introduction
Imagine walking onto your patio on a warm July afternoon and being greeted by a lush display of rose-like blooms in shades of apricot, scarlet, and lemon yellow. Tuberous begonias are the gems of the shade garden, offering a level of color and elegance that few other plants can match in lower light. At Longfield Gardens, we enjoy helping gardeners transform dim corners of the yard into vibrant retreats with these high-performing tropical plants.
This guide is designed for home gardeners who want to master the art of growing tuberous begonias outdoors, whether in garden beds or decorative containers. Tips for Growing Tuberous Begonias can also be a useful companion read, and we will cover everything from selecting the right varieties to the simple steps for overwintering so you can enjoy these plants year after year. By focusing on a few essential basics—like proper drainage, filtered light, and timing—you can achieve professional-looking results in your own backyard.
Choosing the Right Tuberous Begonia for Your Space
Before you get your hands in the dirt, it helps to understand that tuberous begonias generally fall into two categories based on how they grow: upright and trailing. Selecting the right growth habit is the first step toward a successful design.
Upright Begonias for Borders and Beds
Upright double begonias grow on sturdy, succulent stems that reach about 12 to 18 inches tall. These varieties produce large, often double flowers that face outward or slightly upward. They are perfect for the front of a flower bed or for adding height to the center of a container. Popular choices like the Nonstop series are excellent because they live up to their name, blooming reliably from early summer until the first frost.
Cascading Begonias for Hanging Baskets
If you want flowers that spill over the edges of a window box or hanging basket, look for hanging begonias. Varieties like the Illumination series have more flexible stems that naturally drape downward. These create a "waterfall" effect of color, which is ideal for porches or balconies where the flowers can be viewed at eye level.
Selecting Quality Tubers
At Longfield Gardens, we provide premium 5/6 cm tubers because larger tubers have more stored energy. Our 100% Quality Guarantee is part of that promise. This extra energy results in a stronger root system, more stems, and a more impressive display of flowers. When your tubers arrive, they should feel firm and heavy for their size, similar to a healthy potato. If you see small pink or green "eyes" (sprouts) starting to emerge from the hollow side, that is a great sign that the plant is ready to grow.
Key Takeaway: Match the begonia's growth habit to its home. Use upright varieties for garden beds and cascading varieties for hanging containers.
Finding the Perfect Outdoor Location
Tuberous begonias are tropical plants native to the forest floors of South America. Their natural environment provides a blueprint for where they will thrive in your yard.
Light Requirements: The "Bright Shade" Rule
The most common question gardeners ask is how much sun these plants can handle. While they are famous shade-lovers, they do need light to produce those massive blooms. The ideal spot provides "dappled" or "filtered" sunlight—the kind of light that peeks through the canopy of a high tree. If you're not sure about your planting zone, the Hardiness Zone Map is a quick way to check.
In cooler northern climates, tuberous begonias can often handle some gentle morning sun. However, the hot, midday sun in southern regions can be too intense and may scorch the leaves. If you notice the leaf edges turning brown and crispy, the plant is likely getting too much direct light. Conversely, if the stems are getting long and "leggy" with few flowers, it needs a bit more brightness.
Protection from the Elements
Because begonias have thick, succulent stems that are full of water, they can be somewhat brittle. A sudden gust of wind or a heavy downpour can snap a stem. Choose a location that is relatively sheltered, such as near a house wall, under a covered porch, or tucked behind a sturdy shrub.
Soil and Drainage
"Drainage" is a word gardeners use to describe how quickly water moves through the soil. Tuberous begonias are very sensitive to "wet feet," which means they do not like to sit in soggy earth.
- For Containers: Always use a high-quality potting mix and ensure the pot has at least one drainage hole.
- For Garden Beds: If your soil is heavy clay, it will hold water like a sponge. You can improve this by mixing in compost or peat moss to create a lighter, fluffier texture that allows air and water to move freely.
Timing Your Planting for Success
In gardening, timing often matters more than any special fertilizer or "secret" tip. Because tuberous begonias are tropical, they have no tolerance for frost or even chilly soil.
The 50°F Night Rule
You should only move your begonias outdoors when the danger of frost has completely passed and nighttime temperatures are consistently above 50°F. In many parts of the US, this is usually around late May or early June. Planting too early into cold, damp soil is the most common reason for a slow start.
Starting Tubers Indoors
If you live in a region with a short growing season, we recommend starting your tubers indoors about 8 to 12 weeks before the last frost. This "head start" allows the plant to develop a strong root system and foliage while it’s still cold outside. By the time the weather warms up, you’ll have a well-established plant ready to bloom. For a fuller walkthrough, see our How Do I Plant Begonias? A Simple Step-by-Step Guide.
What to do next:
- Check your local frost dates using a reliable weather guide.
- Prepare your containers or garden beds a week before planting by loosening the soil.
- Monitor nighttime temperatures to ensure they stay above 50°F.
Step-by-Step Guide to Planting Tuberous Begonias
Planting a begonia tuber is a simple process, but there is one detail you must get right: which side faces up. If you want more detail on planting depth, see How Deep to Plant Tuberous Begonias for Best Blooms.
Identifying the Top and Bottom
A begonia tuber looks a bit like a dark brown, hairy saucer. One side is rounded (the bottom), and the other side has a distinct hollow or "dip" in the center (the top). You want to plant the tuber with the hollow side facing up. If you see tiny sprouts already starting, those will always emerge from the hollow side.
Depth and Spacing
- For Garden Beds: Dig a shallow hole and place the tuber inside. Cover it with only about 1 inch of soil. If you bury it too deeply, the sprouts may struggle to reach the surface. Space the tubers about 12 inches apart to allow for good air circulation.
- For Containers: Fill your container with moist potting mix, leaving about 2 inches of space at the top. Place the tuber on the surface and cover with 1 inch of mix. In a 12-inch pot, you can plant three tubers for a very full look.
Initial Watering
After planting, water the soil lightly once to settle it around the tuber. Then, be patient. Avoid watering again until you see the first green sprouts emerge, which usually takes 2 to 4 weeks. Overwatering a dormant tuber can cause it to rot before it ever gets a chance to grow.
Key Takeaway: Plant begonias with the hollow side up, just 1 inch below the soil surface. Wait for sprouts to appear before you start a regular watering routine.
Caring for Your Begonias Throughout the Summer
Once your begonias are established and growing outdoors, they are relatively low-maintenance, but they do appreciate consistent attention to water and food.
Watering Correctly, Not Constantly
Begonias prefer soil that is "evenly moist." A good rule of thumb is to stick your finger about an inch into the soil. If it feels dry, it's time to water. If it still feels damp, wait a day.
- Water at the Base: Try to apply water directly to the soil rather than over the leaves. Wet foliage, especially in humid weather, can lead to mildew.
- Morning is Best: Watering in the morning gives the plant the hydration it needs to face the heat of the day and allows any accidental leaf splashes to dry before evening.
Feeding Heavy Bloomers
It takes a lot of energy to produce those large, spectacular flowers all summer long. To keep the show going, begonias need regular fertilization. We recommend using a balanced, water-soluble fertilizer (like a 20-20-20 mix) once every two weeks. If you prefer, you can use a slow-release granular fertilizer at the time of planting, but a liquid boost during the peak of summer (July and August) will really help the plants thrive. For a broader overview, see All About Begonias.
Grooming for a Neat Garden
Tuberous begonias are mostly "self-cleaning," meaning they will eventually drop their old flowers. However, you can keep the plant looking its best by snapping off spent blooms at the stem. This not only keeps the garden looking tidy but also encourages the plant to put its energy into new flower buds rather than seed production.
Supporting Tall Plants
Upright varieties with very large flowers can sometimes become "top-heavy." If you notice a stem starting to lean, you can gently support it with a small bamboo stake and a piece of soft garden twine. Be careful when inserting the stake so you don't poke through the tuber underground; place it a few inches away from the center of the plant.
Understanding the "Male and Female" Flowers
A fun fact about tuberous begonias is that they produce both male and female flowers on the same plant. They usually grow in clusters of three. The large, showy, double flowers are the males. The smaller, simpler flowers on either side are the females. In most garden settings, we leave both on the plant for a full look, but if you are growing begonias for a flower show, some experts remove the female flowers so the plant can focus all its energy on making the male flowers as large as possible.
Moving Begonias Indoors for the Winter
Since tuberous begonias are tender perennials, they don't have to be a one-season wonder. You can save the tubers and replant them next spring. For step-by-step storage advice, see Can You Bring Begonia Plants Inside for the Winter?.
When to Bring Them In
The signal to start the overwintering process is the first light frost of autumn. The cold will turn the foliage yellow or black, which tells the plant it's time to go dormant. At this point, the tuber has pulled all the nutrients from the leaves and stored them for next year.
The Lifting and Curing Process
- Dig Gently: Use a garden trowel to lift the tubers from the ground or container. Keep a bit of soil attached to the roots for now.
- Dry Out: Place the plants in a dry, frost-free area like a garage or shed for about a week. As the stems dry, they will eventually pull away from the tuber with a gentle tug. If they don't come away easily, let them dry a few more days.
- Clean and Store: Brush off any remaining dry soil. Place the tubers in a box filled with dry peat moss, sawdust, or even crumpled newspaper.
- The Ideal Environment: Store the box in a cool, dark, and dry place where temperatures stay between 40°F and 50°F. A basement or a cool closet usually works well.
What to do next:
- Mark your calendar for the first expected frost in your area.
- Gather some cardboard boxes and newspaper in late September so you are ready.
- Check stored tubers once a month during winter to ensure they aren't shriveling (too dry) or getting soft (too damp).
Creating Beautiful Combinations
Tuberous begonias play well with other shade-loving plants. For more pairing ideas, see our companion plants guide. Because they have such bold textures and bright colors, they often serve as the "focal point" in a mixed arrangement.
Container Partners
In a large patio pot, try pairing upright begonias with trailing plants that have similar light and water needs.
- Foliage Contrast: The silver leaves of Dichondra 'Silver Falls' or the chartreuse foliage of a 'Sweet Caroline' sweet potato vine provide a stunning contrast to the deep greens and bright reds of begonias.
- Texture Mix: Combine begonias with the airy, delicate flowers of lobelia or the colorful, patterned leaves of coleus.
In the Landscape
If you are planting in the ground, begonias look wonderful tucked in front of hostas. The large, flat leaves of hostas provide a calm, green backdrop that makes the intricate, rose-like begonia blooms pop.
Ferns also make a soft, textural backdrop that makes the intricate, rose-like begonia blooms pop.
Summary of Success for Growing Tuberous Begonias Outdoors
Growing these stunning flowers doesn't require a green thumb; it just requires a bit of attention to the plant's tropical nature. By waiting for warm weather, providing a "bright shade" environment, and ensuring the soil stays moist but never soggy, you can enjoy a season of nonstop color.
At Longfield Gardens, we take pride in seeing our customers succeed. Gardening should be a source of joy and relaxation, and few plants provide as much visual "reward" for such a simple amount of care as the tuberous begonia.
Final Takeaway Checklist:
- Wait until nighttime temperatures are consistently above 50°F before planting outdoors.
- Use a location with filtered light and protection from harsh winds.
- Plant the tuber hollow-side up, just an inch below the surface.
- Fertilize every two weeks during the peak summer months.
- Save your tubers in the fall to enjoy them again next year.
"The secret to beautiful begonias is patience in the spring and consistency in the summer. Once they start blooming, they won't want to stop until the frost arrives."
FAQ
Why are the flower buds falling off my begonia?
Flower bud drop is usually a sign of stress, most often caused by extreme temperatures or inconsistent watering. If the soil gets bone-dry and then is suddenly drenched, the plant may drop buds. Similarly, a string of exceptionally hot days (over 90°F) can cause the plant to pause. Keeping the soil evenly moist and providing plenty of shade during heatwaves will help.
Do I need to deadhead tuberous begonias?
Tuberous begonias are mostly self-cleaning, but they look much better if you remove the spent flowers yourself. This prevents the old, decaying petals from sitting on the leaves, which can sometimes lead to fungal issues like botrytis. Removing the old blooms keeps the plant looking fresh and encourages new buds to open.
Can I grow tuberous begonias in full sun?
Most traditional tuberous begonias will struggle in full sun, especially in the afternoon. However, some newer hybrids have been bred for better sun tolerance. If you have a sunnier spot, look for varieties specifically labeled as sun-tolerant. Even then, they will perform best if they get a break from the sun during the hottest part of the day and receive plenty of water.
Why are the leaves on my begonia turning yellow?
Yellow leaves are most often a sign of overwatering. If the soil is constantly saturated, the roots cannot breathe, which leads to yellowing and eventually rot. Always check the top inch of soil before watering; if it feels wet, let it dry out a bit more. Ensuring your containers have proper drainage holes is also essential for healthy green foliage.