When to Plant Out Begonias for a Summer Full of Color

Table of Contents

1. Introduction
2. The Importance of Timing with Begonias
3. Starting Begonias Indoors vs. Planting Directly Outside
4. When to Plant Out Based on Begonia Type
5. Knowing Your USDA Hardiness Zone
6. The Art of Hardening Off
7. Choosing the Right Spot for Planting Out
8. How to Plant Out Your Begonias
9. Maintaining Your Begonias Throughout the Season
10. Troubleshooting Common Early-Season Issues
11. Why Begonias are Worth the Wait
12. Conclusion
13. FAQ

Introduction

There is a special kind of excitement that comes with planning a shade garden. While many flowering plants crave the intense heat of the midday sun, begonias offer a lush, colorful alternative for those cooler, quieter corners of your yard. Whether you are envisioning cascading blooms in a hanging basket or a vibrant border of wax begonias, these plants are known for their reliability and stunning variety. At Longfield Gardens, we enjoy helping gardeners find the perfect balance of timing and care to ensure their outdoor spaces look their best from early summer until the first frost.

In this guide, we will focus on exactly when to plant out begonias to ensure they transition smoothly from their starting pots to your garden beds or patio containers. This information is designed for anyone looking to brighten their landscape with these tropical favorites, from first-time gardeners to seasoned pros. If you want a trailing display, browse our hanging begonias.

Success with begonias begins with patience, as waiting for the right outdoor conditions is the most important step you can take.

The Importance of Timing with Begonias

Begonias are tropical and subtropical plants by nature. They thrive in humidity and warmth, which means they have very little tolerance for the cold. If you plant them out too early, the cool soil and chilly nights can stunt their growth or cause the tubers to rot. The goal is to wait until the outdoor environment matches the warm, tropical conditions they love.

The most important factor in determining when to plant out begonias is your local frost-free date. Frost is the primary enemy of the begonia; even a light overnight frost can turn healthy leaves into mush. However, it is not just about avoiding frost. Begonias also need warm soil and steady nighttime temperatures to truly take off.

Watching the Thermometer

Before moving your begonias outside, you should monitor both the air and soil temperatures.

• Nighttime Air Temperature: Wait until the low temperatures at night are consistently above 50°F. If the nights are still dipping into the 40s, it is best to keep your plants indoors or in a protected area.
• Soil Temperature: Begonias prefer soil that has warmed to at least 60°F. In many parts of the country, the soil takes a few weeks to catch up to the air temperature in the spring.

Key Takeaway: If you aren't sure if the soil is warm enough, a simple soil thermometer can help. If the ground feels cold and clammy to your hand, it is likely too early for your begonias.

Starting Begonias Indoors vs. Planting Directly Outside

When you decide to plant out begonias often depends on whether you started them indoors or are planting dormant tubers directly into the ground.

Starting Indoors for Earlier Blooms

Many gardeners choose to "wake up" their begonia tubers indoors about 8 to 12 weeks before the last frost date. For step-by-step help, see How to Start Tuberous Begonias Indoors. This gives the plants a significant head start. By the time the weather is warm enough to move them outside, you will already have a well-established plant with several leaves and potentially even the first few flower buds.

Starting indoors is a great way to extend your blooming season. Because begonias take a little while to get going, starting them in March or April (depending on your zone) ensures you have a full display of flowers by early summer.

Planting Directly Outdoors

If you prefer to plant your tubers directly into the garden or outdoor containers, you must wait until the soil is warm and all danger of frost has passed. For many northern states, this might not be until late May or early June. While this method is simpler and requires less indoor space, it does mean your begonias will start blooming later in the summer.

When to Plant Out Based on Begonia Type

Not all begonias are exactly the same, and their growth habits can influence when they are ready for the great outdoors.

Tuberous Begonias

These are the showstoppers often found in upright double begonias. They grow from thick, potato-like tubers. Because these tubers store a lot of moisture, they are particularly sensitive to cold, wet soil. If you plant them out when the ground is still soggy and cold from spring rains, they are at high risk for rot. Wait for a stretch of warm, dry weather before placing these in the ground.

Wax Begonias (Fibrous-Rooted)

Wax begonias are often sold as "bedding plants" in cell packs at local nurseries. These are slightly more resilient than tuberous varieties but still require warm weather. For a deeper look at planting and care, see How to Plant Wax Begonias for Vibrant Season-Long Color. Because they are usually already growing in soil when you buy them, they can be planted out as soon as the nighttime temperatures stay above 50°F.

Rex and Angel Wing Begonias

These varieties are frequently grown for their dramatic foliage. While they can live outdoors in the summer, they are often treated as houseplants. If you plan to move your indoor begonias to a shaded porch for the summer, wait until the humidity has risen and the nights are warm. They are even more sensitive to temperature swings than the bedding varieties. For a closer look at light needs, see Is a Begonia a Shade Plant? Discover Light Needs & Care.

Knowing Your USDA Hardiness Zone

Your location plays a massive role in your planting schedule. We use the USDA Hardiness Zone map to help coordinate shipping and planting times.

• Zones 8–11: In these warmer climates, begonias can often be planted out much earlier in the spring, sometimes as early as March. In the frost-free parts of Zone 10 and 11, they may even act as perennials.
• Zones 3–7: In these regions, the "waiting game" is more important. A late spring cold snap is common, so it is often wise to wait until late May or even the first week of June to be completely safe.

The Art of Hardening Off

You cannot simply move a begonia from a cozy, warm windowsill directly into the garden. The transition from a controlled indoor environment to the unpredictable outdoors is stressful for plants. This transition process is called "hardening off."

Hardening off allows the plant to toughen up its leaf cuticles and adjust to the intensity of outdoor light and wind. If you skip this step, the leaves may scorch, turn white, or drop off entirely.

A Simple 7-Day Hardening Off Schedule

1. Day 1: Place your begonias in a fully shaded, sheltered spot for just one to two hours, then bring them back inside.
2. Day 2: Leave them in the shade for three to four hours.
3. Day 3: Increase their time to five or six hours.
4. Day 4: Let them stay out all day in the shade. Bring them in at night.
5. Day 5: If the variety can handle a little morning sun, give them one hour of dappled sunlight, then move them back to the shade.
6. Day 6: Leave them out overnight, provided the temperature is forecasted to stay above 55°F.
7. Day 7: Your begonias are now ready to be planted in their permanent outdoor home.

What to do next:

• Check your local 10-day weather forecast.
• Look for a stretch of days with consistent lows above 50°F.
• Begin the hardening off process during a week of mild weather.

Choosing the Right Spot for Planting Out

Once the timing is right, the location is the next piece of the puzzle. Begonias are famous for their love of shade, but "shade" can mean different things. For more guidance on light levels, read Where to Plant Begonias: Sun or Shade? Expert Guide.

Light Requirements

Most begonias thrive in filtered light or dappled shade. Imagine the light under a tall tree or on a porch that gets a little bit of morning sun but is protected during the heat of the afternoon.

• Too much sun: The leaves may turn brown and crispy at the edges.
• Too much shade: The plant may become "leggy" (stretched out) and produce fewer flowers.

Soil and Drainage

"Drainage" is a word gardeners use to describe how fast water leaves the soil. Begonias have fleshy stems that store water, which makes them prone to rotting if they sit in a puddle. For container planting details, see How to Plant Tuberous Begonias in Pots: A Step-by-Step Guide.

• In the garden: Choose a spot where the soil is loose and crumbly. If your soil is heavy clay, consider planting in a raised bed or adding compost to help loosen it up.
• In containers: Always use a pot with a drainage hole. A high-quality potting mix is better than "garden soil" for containers because it is designed to let air reach the roots while holding just enough moisture.

How to Plant Out Your Begonias

When you are finally ready to put your begonias in the ground or their final pots, following a few simple steps will help them settle in quickly.

Spacing and Depth

Proper spacing allows for air circulation, which prevents fungal issues like powdery mildew. For more on spacing, see How Far Should Begonias Be Planted? Expert Spacing Tips.

• Tuberous Begonias: Space them about 8 to 12 inches apart.
• Wax Begonias: These can be planted closer, about 6 to 8 inches apart, to create a dense carpet of color.
• Planting Depth: If you are planting a tuber that has already sprouted, the top of the tuber should be just below the soil surface (about 1 inch deep). If you are transplanting a started plant from a pot, plant it at the same depth it was growing in its original container. For more detail, read How Deep Should Begonias Be Planted for Success?

The "Hollow Side Up" Rule

If you are planting dormant tubers, take a close look at the shape. Tuberous begonias usually have a side that is slightly indented or hollow, like a shallow bowl. This hollow side should always face upward. This is where the new stems will emerge. The rounded side should face down into the soil.

Initial Watering

After planting, give your begonias a gentle drink of water. This helps settle the soil around the roots and removes any large air pockets. However, do not overwater. The soil should be moist like a wrung-out sponge, not soaking wet.

Maintaining Your Begonias Throughout the Season

Knowing when to plant out begonias is just the beginning. Once they are established, a little bit of regular care will keep them blooming until autumn.

Watering Correctly

The best rule for watering begonias is to let the top inch of soil dry out before watering again. Stick your finger into the soil; if it feels dry, it is time for a drink. Try to water at the base of the plant rather than over the leaves. Wet leaves in a shaded area can lead to spotting or mildew.

Feeding Your Plants

Begonias are "heavy feeders," meaning they use a lot of energy to produce those constant blooms.

• Initial Feeding: You can mix a slow-release fertilizer into the soil at planting time.
• Ongoing Feeding: Use a balanced, water-soluble fertilizer every two to three weeks during the peak of summer. This provides the nutrients the plant needs to keep the flower show going.

Deadheading for More Blooms

"Deadheading" simply means removing flowers that have faded or turned brown. For many begonias, this encourages the plant to put its energy into making new buds rather than setting seeds. It also keeps your garden looking tidy. Some modern varieties are "self-cleaning," meaning the old flowers fall off on their own, but a quick cleanup once a week never hurts.

Troubleshooting Common Early-Season Issues

Even with perfect timing, nature can sometimes throw a curveball. Here is how to handle a few common situations.

A Surprise Cold Snap

If you have already planted your begonias and the forecast suddenly calls for a dip near freezing, don't panic.

• For containers: Simply move them back into a garage or mudroom for the night.
• For garden beds: Cover the plants with an old bedsheet or a frost blanket. Remove the cover as soon as the sun comes up the next morning.

Yellowing Leaves

If your begonias develop yellow leaves shortly after being planted out, it is often a sign of too much water. Check the soil drainage. If the area is very wet, you may need to hold off on watering for several days to let the roots breathe.

Slow Growth

If your plants seem to be sitting still and not growing, they are likely waiting for more heat. As the days get longer and the temperatures rise in June and July, begonias typically hit a "growth spurt." As long as the foliage looks healthy and green, a little bit of patience is all that is required.

Why Begonias are Worth the Wait

It can be tempting to rush into the garden on the first warm day of April, but begonias truly reward those who wait for the right conditions. By ensuring the soil is warm and the frost has passed, you avoid the stress of stunted growth and potential loss. For more inspiration on shade-friendly planting ideas, explore our summer flowers for shade.

Begonias offer a versatility that few other shade plants can match. From the delicate, waxy petals of bedding varieties to the giant, rose-like blossoms of tuberous types, they bring life to the parts of the yard that might otherwise stay green and plain. They are also excellent companions for other shade lovers like hostas, ferns, and caladiums.

At Longfield Gardens, we want your gardening experience to be as rewarding as possible. By following these simple rules of timing and temperature, you can enjoy the lush, tropical beauty of begonias all summer long.

Final Thought: Gardening is a rhythmic activity. The wait for the perfect planting day is part of the journey. Once those first vibrant begonia blooms appear, you will know the patience was worth it.

Conclusion

Successfully planting out begonias is all about matching the plant’s tropical needs with your local climate. By waiting for warm soil, consistent nighttime temperatures above 50°F, and a clear frost-free forecast, you give your begonias the best possible start. Remember to take the time to harden them off so they can adjust to their new outdoor home without stress.

• Wait for the warmth: Soil should be 60°F and nights should be 50°F+.
• Acclimate slowly: Spend a week hardening off indoor-started plants.
• Prioritize drainage: Ensure pots and garden beds don't hold standing water.
• Feed and water: Keep soil moist (not wet) and fertilize regularly for maximum blooms.

We invite you to explore the wide variety of colors and textures available at Longfield Gardens to find the perfect begonia flower bulbs for your home. With a little bit of planning and the right timing, your shade garden will be the highlight of the season.

FAQ

Can I plant begonias outside if it is still raining a lot?

It is better to wait until the heaviest spring rains have passed. While begonias like moisture, cold and soggy soil can cause the tubers to rot before they have a chance to grow strong roots. If your garden stays very wet, consider planting your begonias in containers where you can better control the moisture levels. For more details, see Can Begonias Be Planted in Pots? Container Garden Guide.

What should I do if my begonias arrive before it is time to plant them?

If your tubers arrive from us and it is still too cold outside, keep them in a cool, dry, and dark place like a basement or pantry. You can also start them in small pots indoors to give them a head start. This allows the plant to begin developing roots and stems in a protected environment until the outdoor weather is suitable. If you need timing details, check our Shipping Information.

Do begonias need a lot of sun to bloom?

No, most begonias actually prefer shade or partial shade. While they need some light to produce flowers, direct afternoon sun in many regions is too intense and can scorch their leaves. Dappled sunlight under trees or the bright, indirect light on a north-facing porch is usually ideal for the best bloom production. For a broader look at light preferences, see Is a Begonia a Shade Plant? Discover Light Needs & Care.

How do I know if my begonia tuber is still alive?

A healthy begonia tuber should feel firm and heavy for its size, similar to a fresh potato. If the tuber feels light, hollow, or very mushy, it may no longer be viable. When you place a healthy tuber in warm, moist soil, you should see small pink or green "eyes" or sprouts beginning to emerge within two to four weeks. You can also browse begonias to compare different varieties.