How Do You Plant Begonia Bulbs for Summer Color

Table of Contents

1. Introduction
2. Understanding Begonia Bulbs
3. When to Start Your Begonias
4. Choosing the Right Location
5. How to Plant Begonia Bulbs Indoors
6. Moving Your Begonias Outside
7. Summer Care for Best Blooms
8. Exploring Begonia Varieties
9. Safety for Pets and Children
10. Overwintering Begonia Tubers
11. Conclusion
12. FAQ

Introduction

Shade gardens often feel like quiet, green retreats, but they can also be home to some of the most spectacular flowers in the summer landscape. Tuberous begonias are the undisputed stars of the shade, offering rose-like blooms in shades of neon orange, soft pink, and buttery yellow. At Longfield Gardens, we believe every gardener should enjoy these versatile plants, whether you have a sprawling woodland backyard or just a small, shaded balcony.

This guide will walk you through everything you need to know about starting and growing these beautiful flowers. For an even earlier start, our How to Start Tuberous Begonias Indoors guide covers the first steps in more detail. We will cover timing, soil preparation, and the specific steps for planting in both containers and garden beds. By following a few simple steps, you can enjoy a season full of lush foliage and nonstop blooms.

Planting begonia bulbs is a straightforward process that rewards your minimal effort with months of high-impact color.

Understanding Begonia Bulbs

Before we dig into the soil, it is helpful to understand what you are planting. While most people call them "bulbs," these begonia tubers actually grow from tubers. A tuber is a thickened underground stem that stores energy for the plant. If you look closely at a begonia tuber, you will see it looks a bit like a dark, hairy potato.

These tubers are remarkably efficient. A single medium-sized tuber can produce a plant that is 12 inches wide and covered in dozens of flowers. Because they store so much energy, they are very reliable bloomers, even for beginners.

It is also important to note that tuberous begonias are tropical plants. They love warmth and humidity but cannot tolerate frost. This characteristic dictates much of our planting schedule and care routine. In most parts of the United States, we treat them as annuals or lift them in the fall to store indoors for the winter.

When to Start Your Begonias

Timing is one of the most important factors when learning how to plant begonia bulbs. Because they are tropical, they need a long growing season to reach their full potential. If you wait until the weather is warm enough to plant them directly outside, you might not see flowers until late summer.

Starting Indoors for an Early Show

The most successful way to grow begonias in cooler climates is to start them indoors. We recommend starting your tubers about 8 to 12 weeks before the last expected frost date in your area. If you need help checking your region, our hardiness zone map is a useful reference.

By starting early, you ensure your begonias are ready to bloom as soon as you move them to the porch or patio. This usually means planting indoors in late February or March for most of the country.

Planting Directly Outdoors

If you live in a warm climate (USDA zones 9 through 11) or prefer to wait, you can plant tubers directly in the ground. However, you must wait until the soil is warm and there is absolutely no danger of frost. The nighttime temperatures should consistently stay above 60°F. Begonias planted in cold, damp soil are likely to sit dormant or even rot before they get a chance to grow.

Key Takeaway Starting begonias indoors 2 months before the last frost gives you a much longer blooming season. Only move them outside once the nights are reliably warm.

Choosing the Right Location

Begonias are famous for their love of shade, but "shade" can mean many things. Finding the right balance of light and protection will help your plants thrive without burning or becoming "leggy" (stretching toward the light).

Light Requirements

Tuberous begonias prefer filtered light or dappled shade. A spot under a leafy tree or on a porch that gets morning sun and afternoon shade is perfect. While they can handle some morning sun, the intense heat of the afternoon sun can scorch their tender leaves and wilt the heavy blooms.

If you find your begonias are producing lots of leaves but very few flowers, they might be in too much shade. If the leaves look yellow or have brown, crispy edges, they are likely getting too much direct sun.

Soil and Drainage

The most important rule for begonia soil is that it must drain well. Drainage simply refers to how fast water leaves the soil. Begonia tubers are susceptible to rot if they sit in puddles.

If you are planting in the garden, look for a spot where water doesn't collect after a rainstorm. You can improve your garden soil by mixing in some compost or shredded bark to lighten the texture. For containers, always use a high-quality potting mix rather than garden soil. Potting mix is designed to stay fluffy and allow air to reach the roots, which begonias love.

Protection from Wind

Begonias have thick, succulent stems that are full of water. This makes them somewhat brittle. Large-flowered varieties or trailing "pendula" types can be damaged by strong summer winds. Choose a spot that is somewhat sheltered, such as near a fence, a wall, or on a covered patio.

How to Plant Begonia Bulbs Indoors

Starting your tubers in pots indoors is a fun way to beat the winter blues. It is a simple process that requires just a few supplies: tubers, pots, and potting soil. For more planting and aftercare details, see our Tips for Growing Tuberous Begonias.

Step 1: Identify the Top and Bottom

This is the part that confuses most new gardeners, but it is quite simple once you know what to look for. Begonia tubers are shaped like a shallow bowl or a saucer. One side is indented (concave), and the other side is rounded (convex).

The indented, "hollow" side is the top. This is where the pinkish buds or "eyes" will sprout. The rounded side is the bottom, where the roots will grow. Always plant the tuber with the hollow side facing up.

Step 2: Prepare the Container

You can start tubers in individual 4-inch or 6-inch pots, or you can use a shallow tray. Ensure the container has drainage holes in the bottom. Fill the container with slightly moist potting soil, leaving about an inch of space at the top.

Step 3: Placing the Tuber

Place the tuber on top of the soil with the hollow side up. You do not need to bury begonias deeply. In fact, they prefer to be just barely covered. Press the tuber gently into the soil so it makes good contact, then sprinkle just enough soil over the top to hide it from view (about 1/2 inch of soil is plenty).

Step 4: Warmth and Light

Begonia tubers need warmth to "wake up." Place the pots in a warm room where the temperature stays around 60°F to 70°F. They do not need light until the first green sprouts appear. Once you see growth poking through the soil, move the pots to a bright window or under grow lights.

Step 5: Careful Watering

This is the most critical stage. Until the tuber has sprouted leaves, it does not have a way to process a lot of water. Keep the soil lightly moist—like a wrung-out sponge—but never soggy. Watering too much at this stage is the most common reason tubers fail to grow.

Moving Your Begonias Outside

Once the weather has warmed up and your indoor starts are growing vigorously, it is time to move them to their summer home. If you are still waiting on your order, our Shipping Information page explains how orders are scheduled.

The Hardening Off Process

You cannot move a plant directly from a cozy indoor windowsill to the outdoor garden without a transition period. This is called "hardening off."

Start by placing your pots in a sheltered, shady spot outside for a few hours during the day. Bring them back inside at night. Over the course of 7 to 10 days, gradually increase the amount of time they spend outside and the amount of light they receive. This toughens up the leaves and prevents transplant shock.

Planting in the Ground

If you are moving your begonias into a garden bed, space them about 8 to 12 inches apart. This gives each plant enough room for air to circulate, which helps prevent mildew. Dig a hole that is just deep enough to accommodate the root ball of your started plant. Set the plant in the hole so the base of the stems is level with the soil surface.

Planting in Containers

Begonias are arguably the best container plants for shade. For a standard 12-inch hanging basket or patio pot, we suggest planting three tubers. This creates a full, lush look that overflows with color.

If you are using trailing begonias, such as the Pendula type, plant them near the edges of the pot so they can cascade over the sides. Upright varieties, like the Roseform or Fimbriata types, should go in the center to provide height and structure.

What to Do Next

• Check the 10-day weather forecast for any late frosts.
• Prepare your pots with fresh, high-quality potting mix.
• Begin the hardening off process by moving plants to a shady porch for 2 hours.
• Gradually increase outdoor time over a week before final planting.

Summer Care for Best Blooms

Once your begonias are settled in, they are relatively low-maintenance. However, a little consistent attention will keep them blooming from midsummer all the way until the first frost of autumn.

Watering Rules

Begonias like "consistent moisture." This means the soil should not dry out completely, but it should also not be a swamp. In the heat of summer, container plants may need water every day.

To check if it is time to water, stick your finger an inch into the soil. If it feels dry, give them a drink. Try to water at the base of the plant rather than over the leaves. Wet leaves in a shady spot can lead to fungal issues like powdery mildew.

Feeding Your Plants

Because begonias bloom so prolifically, they are "heavy feeders." They need a regular supply of nutrients to keep producing those big flowers. We recommend using a balanced, water-soluble fertilizer every two weeks throughout the growing season. Follow the instructions on the fertilizer label for the correct dosage.

Deadheading and Grooming

"Deadheading" is the process of removing faded flowers. Tuberous begonias are generally self-cleaning, meaning the old flowers will eventually fall off on their own. However, picking off the spent blooms helps the plant look tidy and encourages it to put more energy into new buds.

You should also remove any yellowing or damaged leaves you see throughout the season. This keeps the plant healthy and allows for better airflow through the foliage.

Exploring Begonia Varieties

One of the joys of growing begonias is the incredible diversity of flower shapes and sizes. When we select varieties for our gardens, we consider how the plant will be used. For more options in this group, browse our Upright Double Begonias.

Upright Begonias

These varieties grow 12 to 15 inches tall and are perfect for garden borders or the center of a pot.

• Roseform Pink: These produce massive, double blooms that look exactly like roses. They are often 4 to 6 inches across.
• Fimbriata (Fringed): These have unique, ruffled petals that look like carnations. They add a wonderful texture to the garden.
• Picotee White: These are bi-color flowers where the edges of the petals are a different color than the center, creating a stunning "painted" effect.

Trailing Begonias (Pendula)

These are bred specifically for hanging baskets and window boxes. Instead of growing straight up, the stems arch outward and hang down. They are covered in hundreds of slightly smaller flowers, creating a "waterfall" of color.

Fragrant Begonias

While most begonias are grown for their looks, some varieties offer a delightful, sweet scent. These are perfect for pots on a patio table or near an entryway where you can enjoy the fragrance as you pass by.

Safety for Pets and Children

It is important to note that begonias contain calcium oxalates, which can be toxic if ingested. This is primarily a concern for pets like dogs and cats, as well as curious young children.

Ingesting the plant can cause irritation of the mouth and throat, drooling, or vomiting. We recommend planting begonias in hanging baskets or raised containers if you have pets that like to nibble on greenery. Always keep dormant tubers stored in a safe place away from reach.

Overwintering Begonia Tubers

As the summer comes to a close and the first frost approaches, you have a choice. You can treat your begonias as annuals and start with fresh tubers next spring, or you can save your tubers to plant again.

Letting the Plant Go Dormant

In late fall, when the leaves start to turn yellow and the plant looks a bit tired, stop fertilizing and reduce watering. This signals to the plant that it is time to rest. After the first light frost kills the top growth, cut the stems back to about an inch above the tuber.

Storing the Tubers

If your begonias were in the ground, carefully dig them up. If they were in pots, you can simply pull the tubers out of the soil. Shake off the excess dirt and let the tubers dry in a cool, shady spot for a few days.

Once dry, store the tubers in a cardboard box or paper bag filled with peat moss, vermiculite, or sawdust. Keep the box in a cool, dark, and dry place (like a basement or closet) where the temperature stays between 40°F and 50°F. Do not let them freeze. Next spring, you can pull them out and start the process all over again.

Conclusion

Planting begonia bulbs is one of the most rewarding ways to transform a shady corner into a vibrant display of color. By starting your tubers indoors, choosing a spot with filtered light, and ensuring they have well-drained soil, you can enjoy spectacular blooms all summer long. These plants are durable, versatile, and accessible to gardeners of every skill level.

At Longfield Gardens, our goal is to help you find success with every tuber you plant, and our About Us page explains our 100% Quality Guarantee. Whether you choose the ruffled petals of the Fimbriata or the cascading beauty of a trailing variety, the effort you put in now will pay off in months of beauty.

• Start tubers indoors 8-12 weeks before the last frost.
• Always plant with the hollow (indented) side facing up.
• Keep the soil moist but never soggy to prevent rot.
• Fertilize every two weeks for maximum flower production.

The secret to a stunning shade garden is often found in the simple begonia tuber—a small package that delivers some of the garden's most dramatic results.

Ready to get started? We invite you to explore our premium begonia tubers to find the perfect colors and shapes for your garden this season.

FAQ

Which side of a begonia bulb is the top?

The top of a begonia tuber is the side with a shallow, bowl-like indentation (the concave side). Sometimes you can see small pink buds or the dried remains of last year’s stems in this hollow area. The rounded, smooth side is the bottom and should be placed against the soil.

Do I need to soak begonia bulbs before planting?

You do not need to soak begonia tubers before planting. While some other types of garden bulbs benefit from a soak, begonias are very sensitive to excess moisture. Simply planting them in pre-moistened potting soil is enough to trigger growth without risking rot.

How long does it take for begonias to sprout?

Begonias are relatively slow starters compared to other summer bulbs. It typically takes 3 to 6 weeks for the first green shoots to appear above the soil. Factors like soil temperature and humidity can influence this; they will sprout faster in a warm room (around 70°F) than in a cool one.

Can begonias grow in full sun?

Most tuberous begonias will struggle in full sun, especially in hot climates. The intense light can burn the foliage and cause the flowers to wilt quickly. They perform best in partial shade, dappled sunlight, or a spot that only receives gentle morning sun and is shaded during the hottest part of the afternoon.