Begonia Bulbs: How to Grow and Care for Them

Table of Contents

1. Introduction
2. Understanding Begonia Tubers
3. Selecting the Best Varieties for Your Space
4. Choosing the Perfect Planting Site
5. When to Start Your Begonias
6. Step-by-Step: Starting Begonias Indoors
7. How to Plant Begonias in the Garden
8. Essential Care for Summer Success
9. Managing Common Challenges
10. Overwintering: Saving Your Tubers for Next Year
11. Growing Begonias in Different Climates
12. Why We Love Tuberous Begonias
13. FAQ

Introduction

Imagine transforming the quiet, shady corners of your yard into a lush retreat filled with vibrant, rose-like flowers. Tuberous begonias are the perfect choice for these spaces, offering some of the most spectacular colors and textures in the gardening world. Whether you want to fill a hanging basket on a covered porch or brighten a woodland border, these plants provide a high-reward experience for a little bit of effort.

At Longfield Gardens, we want to help you succeed with every bulb and tuber you plant. Growing begonias is an achievable goal for gardeners of any skill level, and the results are often breathtaking. These plants are known for their long blooming season, which often stretches from midsummer all the way until the first frost. Longfield Gardens’ 100% guarantee helps make that easier.

In this guide, we will walk you through everything you need to know about growing begonia bulbs. You will learn how to start them indoors, how to transition them to the garden, and how to keep them healthy all summer long. This article is designed to help you feel confident and excited as you start your begonia journey.

Understanding Begonia Tubers

Before you get your hands in the dirt, it helps to understand what you are actually planting. While many people search for "begonia bulbs," these plants actually grow from tubers. A tuber is a thickened, underground part of a stem that stores nutrients for the plant. If you look at a begonia tuber, you will notice it looks quite different from a round tulip bulb or a papery onion.

Begonia tubers are usually brown, somewhat hairy, and have a distinct shape. One side is rounded (convex), and the other side has a hollow or indented area (concave). This "cup" shape is the most important thing to identify before planting. The indented side is where the new growth will emerge. Think of the tuber as a small bowl; you want the bowl to sit upright in the soil so the sprouts can grow straight up toward the sun.

These tubers come in different sizes, and generally, a larger tuber will produce a larger plant with more flowers. They are filled with stored energy, which allows the plant to get a strong start even before you see any leaves above the soil. This built-in energy reserve makes them very resilient, provided they are given the right environment to grow.

Selecting the Best Varieties for Your Space

Not all tuberous begonias grow the same way. When you are planning your garden, it is helpful to choose varieties that match your specific goals. We offer several types that serve different purposes in the landscape.

Upright Begonias

Upright varieties are perfect for garden beds, borders, and traditional patio pots. They grow on sturdy stems that hold the flowers up where they can be easily seen. These often include "Double" begonias, which feature many layers of petals, and "Fimbriata" types, which have fringed edges that resemble carnations.

Trailing or Pendula Begonias

If you are looking to fill hanging baskets or window boxes, trailing begonias (often called Begonia pendula) are the way to go. Summer Blooming Bulbs for Containers are a good fit for that kind of display. These plants have a more flexible growth habit, allowing the stems to cascade over the sides of the container. This creates a waterfall effect of foliage and flowers that looks stunning on a porch or balcony.

Picotee and Specialty Types

For those who love intricate details, Picotee begonias are a wonderful choice. These flowers have a base color with a different, contrasting color along the edges of the petals. They look like they have been hand-painted and add a sophisticated touch to any shaded area.

Key Takeaway: Match the growth habit to your container. Choose upright varieties for pots and beds, and trailing varieties for hanging baskets to get the most beautiful visual impact.

Choosing the Perfect Planting Site

Success starts with picking the right spot. Begonias have specific preferences when it comes to light and soil, and meeting these needs is the easiest way to ensure a summer full of blooms.

Light Requirements

Begonias are famous for their love of shade. In most parts of the country, they do best in filtered light or partial shade. Direct, hot afternoon sun can scorch their succulent leaves and cause the flowers to wilt. A spot under a tall tree, on the north side of a building, or under a covered patio is usually ideal.

If you live in a cooler northern climate, your begonias might handle a bit more morning sun. However, in the hotter southern states, deep shade during the heat of the day is a must. If you notice the leaves looking pale or getting brown, crispy edges, the plant is likely getting too much sun.

Soil and Drainage

"Drainage" is a word you will hear often in gardening. In simple terms, it refers to how fast water leaves the soil. Begonia tubers are sensitive to sitting in soggy ground, which can lead to rot. They prefer soil that is light, porous, and rich in organic matter.

If you are planting in the ground, you can improve your soil by mixing in some compost or finely ground bark. This creates "air pockets" in the soil, allowing excess water to move away from the tuber while keeping enough moisture for the roots to drink. If you see puddles in your garden hours after it rains, that spot may be too wet for begonias.

When to Start Your Begonias

Timing is one of the most important factors when learning how to grow begonia bulbs. Because begonias are tropical plants, they are very sensitive to cold temperatures. They will not survive a frost, and they generally stop growing if the temperature drops below 50°F.

The Advantage of an Early Start

Tuberous begonias have a relatively slow start. It can take several weeks for the first sprouts to appear and a few months before the plant is large enough to flower. To get the most "bloom time" out of your season, we recommend starting the tubers indoors about 8 to 12 weeks before your area's last expected frost date.

By starting them early in late winter or early spring, you give the plants a "head start." By the time the weather is warm enough to move them outside, you will have established plants with plenty of leaves, which means you will see flowers much sooner in the summer.

Checking the Weather

If you choose to plant your tubers directly into the garden without starting them indoors, you must wait until the soil is warm. A good rule of thumb is to wait until the nighttime temperatures are consistently above 60°F. If the soil is cold and damp, the tubers may sit dormant for a long time or potentially rot before they even start to grow. Hardiness Zone Map can help you compare those timing windows for your area.

Step-by-Step: Starting Begonias Indoors

Starting your tubers indoors is a rewarding project that can happen while there is still snow on the ground. It is an easy way to bring a bit of gardening into your home during the winter months.

1. Select Your Containers: You can use individual small pots or a shallow tray with drainage holes. Make sure the containers are clean.
2. Use High-Quality Potting Mix: Choose a potting soil that is light and fluffy. Avoid using heavy garden soil from outside, as it does not drain well in containers and may contain pests.
3. Position the Tuber: Place the tuber with the hollow (indented) side facing up. You do not need to bury it deeply. In fact, many gardeners simply press the tuber into the soil so the top is just barely visible or covered by a very thin layer of mix (about 1/2 inch).
4. Water Sparingly: This is a critical step. Give the soil a light drink to settle the tuber, but do not soak it. Until you see green growth, the tuber does not have roots to drink much water. Overwatering at this stage is a common cause of failure.
5. Provide Warmth and Light: Place the pots in a warm spot (around 70°F). They do not need bright light until the sprouts appear. Once you see green stems poking through the soil, move the pots to a bright window with indirect light or under a grow light.
6. Maintain Moisture: Keep the soil slightly damp to the touch, like a wrung-out sponge. Never let it get soggy, but try not to let it dry out completely.

What to do next: Once your tubers have sprouted and developed a few sets of leaves, they are ready for the next phase. Keep them in their bright, warm indoor spot until the outdoor weather is reliably warm.

How to Plant Begonias in the Garden

Once the threat of frost has passed and the air feels warm, it is time to move your begonias to their permanent summer home. Whether you started them indoors or are planting dormant tubers directly, the process is straightforward.

Hardening Off

If you started your plants indoors, you cannot move them directly into the full outdoor environment all at once. They need to get used to the wind, temperature swings, and outdoor light. This process is called "hardening off." Spend about a week placing your plants outside in a sheltered, shady spot for a few hours a day, gradually increasing their time outside.

Spacing and Depth

If you are planting begonias in a garden bed, space the tubers about 10 to 12 inches apart. This gives the plants enough room to grow and ensures good air circulation, which helps prevent leaf issues later in the season.

If you are planting dormant tubers directly into the ground:

• Dig a shallow hole.
• Place the tuber indented-side up.
• Cover with no more than 1 inch of soil.
• Water lightly.

Container Planting

Many gardeners prefer growing begonias in pots because it is easier to control the soil and drainage. For a 12-inch pot, you can plant 2 to 3 tubers for a very full look. Ensure your pot has drainage holes at the bottom. If the pot sits in a saucer, remember to empty the saucer after watering so the plant doesn't sit in a pool of water.

Essential Care for Summer Success

Once your begonias are established, they are relatively low-maintenance. Following a few simple rules for water and food will keep them performing their best through the heat of summer.

Watering Correctly

Begonias like "consistent" moisture. The goal is to keep the soil damp but not wet. The best way to tell if your plant needs water is to stick your finger an inch into the soil. If it feels dry, it is time to water. If it feels moist, wait another day.

When you water, try to aim the stream at the base of the plant rather than splashing the leaves. Wet foliage, especially in the evening, can sometimes lead to mildew or fungus. Watering in the morning is usually best, as it gives any accidental splashes time to dry in the daylight.

Fertilizing for Blooms

Because begonias bloom so much, they use a lot of energy. Providing them with a little extra "food" will help them produce more flowers. You can use a balanced, water-soluble fertilizer every two weeks during the growing season. Alternatively, you can mix a slow-release fertilizer into the soil at planting time. Following the instructions on the product label is the best way to ensure you are giving them the right amount.

Deadheading and Grooming

"Deadheading" simply means removing flowers that have finished blooming and started to fade. This is not strictly necessary for the health of the plant, but it helps the plant look tidy. It also encourages the plant to put its energy into creating new buds instead of trying to make seeds.

You can also remove any yellow or damaged leaves you see throughout the summer. This keeps the plant looking fresh and improves air circulation. Begonias have somewhat brittle stems, so be gentle when you are working around them to avoid accidentally snapping a branch.

Managing Common Challenges

Gardening always involves a bit of observation. While begonias are generally healthy, there are a few things to look out for. Leading with a proactive approach is better than reacting to a problem.

Mildew and Leaf Health

If you live in a very humid climate, you might notice a white, powdery substance on the leaves. This is usually powdery mildew. The best way to prevent this is to ensure your plants aren't crowded together. Good airflow is a natural defense. As mentioned before, watering at the soil level instead of over the leaves also makes a big difference.

Dropping Flowers

If your begonia suddenly drops its flowers, it is usually a sign of stress. The most common cause is the soil getting too dry. Begonias may drop their blooms to conserve moisture when they feel thirsty. Check the soil moisture levels and try to keep them more consistent. On the flip side, extremely high temperatures (above 90°F) can also cause flower drop. Moving a container-grown plant to a cooler, shadier spot during a heatwave can help.

Staking Tall Varieties

Some upright begonias can produce flowers so large and heavy that the stems begin to lean. If you see this happening, you can gently support the stem with a small bamboo stake and a loose tie. This prevents the stem from snapping during a heavy rain or wind.

Overwintering: Saving Your Tubers for Next Year

One of the best things about tuberous begonias is that they are perennials. This means you don't have to buy new ones every year! If you live in a cold climate (Zones 3-8), you can "overwinter" the tubers indoors and replant them next spring.

The Dormancy Process

As the days get shorter and the temperatures drop in the autumn, your begonias will naturally start to slow down. You will notice the leaves beginning to turn yellow. This is a signal that the plant is moving its energy down into the tuber for the winter.

Lifting and Storing

1. Stop Watering: When the foliage begins to yellow, stop watering the plant. Allow the soil to dry out.
2. Dig Them Up: Before the first hard frost, gently lift the tubers out of the ground or the pot.
3. Clean and Trim: Cut the stems back to about an inch above the tuber. Gently shake off the excess soil, but you don't need to wash them.
4. Dry Them Out: Place the tubers in a cool, dry, protected spot for a few days to let the outer skin "cure" or dry out.
5. Pack for Storage: Place the tubers in a paper bag or a box filled with dry peat moss, sawdust, or vermiculite. This keeps them from drying out completely while still allowing them to "breathe."
6. Store in a Cool Spot: Keep the box in a place that stays cool (around 40-50°F) but never freezes. A basement or a cool closet usually works well.

Key Takeaway: Overwintering is an easy way to grow your begonia collection over time. The tubers often get larger each year, leading to even more spectacular displays every summer.

Growing Begonias in Different Climates

While the basics of how to grow begonia bulbs remain the same, your local weather will play a role in how you manage your plants.

Northern Gardeners

In the North, the growing season is shorter. Starting your tubers indoors is almost essential if you want to see flowers by July. Because summer nights are cooler, your begonias may grow very vigorously once they get outside. You might also find they can handle a bit more morning sun than they could in the South.

Southern Gardeners

In the South, the challenge is the heat. High humidity can be great for begonias, but extreme afternoon temperatures are tough. Southern gardeners should prioritize the shadiest spots in the garden. Using self-watering pots can also be a "win," as they help maintain that consistent moisture begonias crave during a hot Southern summer.

Why We Love Tuberous Begonias

At Longfield Gardens, we see tuberous begonias as one of the best investments a gardener can make for a shaded landscape. They offer a level of flower power that few other shade plants can match. From the moment you see that first tiny sprout in your indoor pot to the afternoon you sit on your porch surrounded by cascading blooms, the process is full of small joys.

Gardening should be a rewarding experience, and begonias fit that description perfectly. They aren't demanding, they don't require full sun, and they reward your care with months of beauty. By getting the basics of drainage, light, and timing right, you can enjoy these stunning flowers year after year. If you plan to plant in larger numbers, Spring Planted Flower Bulk Buys can make it easier to fill more shade spots at once.

• Start tubers indoors 8-12 weeks before the last frost.
• Plant the "cup" side facing up.
• Provide partial to full shade and well-draining soil.
• Keep the soil consistently moist but never waterlogged.
• Store tubers in a cool, dry place over winter to reuse them next year.

Growing begonias is one of the easiest ways to bring professional-looking color to the shady parts of your home. With just a little bit of planning and consistent watering, you can enjoy a tropical-feeling paradise all summer long.

FAQ

Which side of a begonia tuber faces up when planting?

The indented or "hollowed-out" side of the tuber should face up. This side contains the growth points, often called "eyes," which will sprout into stems and leaves. The rounded, smooth side should face down into the soil.

Do I have to start begonia bulbs indoors?

You do not have to start them indoors, but it is highly recommended in most US climates. Begonias grow slowly at first and need warm temperatures. Starting them indoors 8-12 weeks before the last frost ensures you have flowers for the majority of the summer instead of waiting until late August for blooms.

How often should I water my begonias?

You should water your begonias whenever the top inch of soil feels dry to the touch. The goal is to keep the soil consistently moist, like a sponge that has been wrung out. Avoid letting the soil become bone-dry, but also ensure the pots or beds have good drainage so the tubers never sit in standing water.

Can begonias grow in full sun?

Most tuberous begonias prefer partial shade to full shade. In very hot climates, full sun will likely scorch the leaves and cause the flowers to wilt or drop. In cooler northern climates, they may tolerate some morning sun, but they should always be protected from the intense heat of the afternoon sun.