When to Plant Begonia Outside for a Colorful Garden

Table of Contents

1. Introduction
2. The Golden Rule of Temperature
3. Starting Begonias Indoors for an Early Start
4. Transitioning Begonias to the Outdoors
5. Planting by USDA Hardiness Zone
6. Choosing the Best Outdoor Location
7. Understanding Different Begonia Types
8. How to Plant Outdoors Step-by-Step
9. Watering and Feeding for Maximum Blooms
10. Caring for Begonias at the End of the Season
11. Common Questions About Planting Timing
12. Conclusion
13. FAQ

Introduction

There is nothing quite like the excitement of seeing the first rose-like blooms of a tuberous begonia unfurling in a shady corner of the garden. These plants are beloved for their ability to bring saturated color to the areas of your yard where most flowers struggle to grow. At Longfield Gardens, we want to help you enjoy a lush, vibrant display that lasts from midsummer all the way until the first frost of autumn with our Begonia Flower Bulbs for Sale collection.

The most important secret to success with these tropical beauties is getting the timing right. Because begonias are sensitive to cold, knowing exactly when to move them from the safety of your home to the garden is the difference between a slow start and a spectacular show. This guide will help you determine the best planting dates based on your local weather and your specific growing zone, and our All About Begonias guide covers the broader family.

Whether you are starting with bare tubers in late winter or buying established plants in the spring, the goal is the same. We will cover how to read the signals from your local climate so your begonias thrive the moment they hit the soil. Timing your planting correctly ensures your garden stays bright and beautiful all season long.

The Golden Rule of Temperature

Begonias are tropical plants by nature. They originally come from warm, humid regions in South and Central America, Africa, and Asia. Because of this heritage, they have no natural defense against frost or even chilly spring nights. If you want a deeper dive into this group, see our Tips for Growing Tuberous Begonias guide.

We recommend waiting until the soil temperature has reached a consistent 60°F before planting. While the air might feel warm on a sunny April afternoon, the soil takes much longer to heat up. Cold soil can cause begonia tubers to sit dormant or, in some cases, struggle to develop a strong root system. A simple soil thermometer is a great tool to help you take the guesswork out of this process.

In addition to soil temperature, you must watch the overnight lows. Air temperatures should be reliably above 50°F before you move your plants outdoors for good. In many parts of the United States, this means waiting until late May or even early June. If you still see steam when you breathe outside at night, it is too early for your begonias.

Key Takeaway: Begonias love warmth. Wait until the soil is 60°F and night temperatures stay above 50°F to ensure your plants get off to a strong start.

Starting Begonias Indoors for an Early Start

If you live in a northern climate with a short growing season, waiting until June to plant might feel like you are missing out on weeks of color. This is why many gardeners choose to start their begonia tubers indoors. By starting them early, you can have plants that are already blooming by the time the weather is safe enough for them to go outside.

When to Begin the Indoor Process

We suggest starting your begonia tubers indoors about 8 to 12 weeks before your area’s average last frost date. For a step-by-step container approach, see How to Plant Tuberous Begonias in Pots. For most gardeners in the northern half of the country, this means planting the tubers in pots sometime in February or March. This window gives the plant enough time to develop a sturdy root system and several sets of leaves.

How to Start Your Tubers

Starting tubers is a simple process that requires just a few supplies. You will need a shallow tray or individual small pots, a high-quality potting mix, and a warm spot in your home.

1. Check the Tuber: Look for the indented or "hollow" side of the tuber. This is the top where the sprouts will emerge. The rounded side is the bottom.
2. Prepare the Soil: Fill your containers with moist, but not soaking wet, potting mix.
3. Planting Depth: Place the tuber into the soil with the hollow side facing up. Press it down so it is mostly covered, with only about half an inch of soil over the top.
4. Find a Warm Spot: Begonias need warmth to wake up. A room that stays around 70°F is ideal. You do not need bright light until the first green sprouts appear.

Caring for Indoor Sprouts

Once you see the first pink or green nubs breaking through the soil, move the pots to a bright window or under grow lights. Be very careful with water at this stage. The tubers do not have many roots yet, so they cannot drink much. Keep the soil lightly damp. If the soil stays too wet before the plant is actively growing, the tuber may rot.

What to do next: Indoor Starting

• Look up your average last frost date using a local gardening calendar.
• Count back 10 weeks from 그날 to find your ideal indoor planting day.
• Order your tubers from us early to ensure you have the best selection of varieties.
• Set up a warm, draft-free space in your home for the trays.

Transitioning Begonias to the Outdoors

Once the weather finally warms up, you might be tempted to move your lush indoor plants directly into the garden. However, plants that have grown up in the controlled environment of your home need time to adjust to the wind, direct sun, and temperature swings of the outdoors. This process is called "hardening off."

The One-Week Transition Plan

Think of hardening off like a slow introduction. We recommend a seven-day schedule to get your begonias ready for their permanent home:

• Days 1-2: Place the plants in a fully shaded, sheltered spot for just two or three hours in the afternoon. Bring them back inside before the evening chill sets in.
• Days 3-4: Increase the time outside to five or six hours. Move them into a spot that gets a tiny bit of dappled morning light, but keep them protected from heavy wind.
• Days 5-6: Leave the plants outside all day. Bring them in only if the forecast calls for a dip in temperature below 50°F.
• Day 7: If the nights are warm and the plants look strong, they are ready to stay out overnight and be planted in their final location.

Signs of Stress to Watch For

During this transition, keep a close eye on the leaves. If you see white or transparent patches, the plant is getting too much sun too fast. This is essentially a "sunburn." If the edges of the leaves look crispy or frayed, the wind may be too strong. If you notice these signs, simply move the plant back to a more protected spot for another day or two.

Key Takeaway: Never rush the move outdoors. A week of gradual adjustment prevents transplant shock and keeps your begonias healthy and beautiful.

Planting by USDA Hardiness Zone

Your geographic location plays a huge role in when you should plant begonia outside. The USDA Hardiness Zone map is a helpful tool that divides North America into zones based on their average annual minimum winter temperature. Knowing your zone helps you understand your local timeline, and you can check the Hardiness Zone Map before you plant.

Zones 3 through 7

In these cooler northern and central regions, begonias are grown as annuals. The ground freezes in the winter, which would kill the tropical tubers. In these zones, you should almost always start your tubers indoors in late winter to maximize your summer bloom time. Planting outside usually happens between mid-May and mid-June, once the risk of a late-season frost has completely passed.

Zones 8 through 11

In warmer climates, the timeline is much more flexible. In parts of the Deep South, the Southwest, and the West Coast, begonias can sometimes be planted directly into the ground as soon as the soil warms up in March or April. In frost-free areas like Zone 10 or 11, begonias may even survive the winter outdoors, though they still appreciate a rest period.

Shipping and Your Zone

We time our shipping based on these zones. We want to ensure your tubers arrive at the right time for your climate—typically a few weeks before it is time to start them indoors. For more details, see our Shipping Information page. This ensures they spend as little time as possible in a box and as much time as possible growing in your care.

Choosing the Best Outdoor Location

Timing is the first step, but "where" you plant is just as important as "when." Even a perfectly timed planting can fail if the location doesn't meet the plant's needs. Success with begonias follows the "right plant, right place" rule.

Light Requirements: Filtered is Best

Most begonias thrive in partial shade. In the wild, they grow on the forest floor where they receive "filtered" light through the canopy of trees.

• Morning Sun: A spot that gets 2 to 4 hours of gentle morning sun followed by afternoon shade is usually perfect.
• Afternoon Shade: The hot, intense sun of the late afternoon (between 2:00 PM and 6:00 PM) can scorch begonia leaves and cause flowers to wilt.
• Deep Shade: While they love shade, begonias do need some light to produce flowers. If a spot is so dark that moss is the only thing growing there, your begonias might produce lots of leaves but very few blooms.

Soil and Drainage

The word "drainage" simply refers to how fast water leaves the soil. Begonias have fleshy stems and tubers that store a lot of water. Because of this, they are very susceptible to rot if they sit in soggy soil. If you want more detail on planting depth, see How Deep Should Begonias Be Planted for Success?.

• The Sogginess Test: After a heavy rain, look at your planting spot. If water is still standing there six hours later, the drainage is poor.
• Improving Soil: You can improve heavy clay soil by mixing in organic matter like compost or finely ground bark. This creates "air pockets" in the soil that allow water to move through more easily.
• Container Advantage: If your garden soil is heavy, planting in pots or hanging baskets is a great solution. The Begonia Upright Double Superba White is a smart choice for this kind of display.

What to do next: Preparing the Spot

• Observe your garden throughout the day to find spots with filtered morning sun.
• Test your soil drainage by digging a small hole and filling it with water to see how fast it disappears.
• Purchase a high-quality potting mix if you plan to use containers.
• Clear away any weeds or debris from the planting area a week before you plan to move your plants outside.

Understanding Different Begonia Types

Not all begonias are the same, and the type you choose might slightly change your planting strategy. While most follow the same temperature rules, their growth habits vary.

Tuberous Begonias

These are the stars of the shade garden, known for their massive, rose-like flowers. At Longfield Gardens, we offer high-quality 5/6 cm tubers which produce larger plants with more stems. The Begonia Non Stop Mix - Bulk Offer is a good example of the kind of long-blooming tubers many gardeners love.

• Upright Varieties: These grow into sturdy, mounded shapes. They are perfect for garden borders or window boxes where you want the flowers to face up and out. Browse the Upright Double Begonias collection for this habit.
• Hanging or Pendula Varieties: These have a cascading habit. They are specifically bred for hanging baskets where the stems will drape over the edges, creating a waterfall of color. The Hanging Begonias collection is the best fit here.

Wax Begonias

You will often see these in public parks or as "bedding plants." They have smaller, waxy leaves and clusters of small flowers. Wax begonias are much more tolerant of sun than tuberous varieties. If you have a spot that gets a bit more light, wax begonias are a sturdy choice. They are usually grown from fibrous roots rather than tubers.

Rex and Angel Wing Begonias

These are often grown for their spectacular foliage rather than their flowers. Rex begonias have swirls of silver, purple, and green on their leaves. Angel Wing (or Cane) begonias have long, spotted leaves. While these are popular as houseplants, they love spending the summer outside in a shaded, protected spot. They follow the same "no cold" rule as tuberous begonias.

How to Plant Outdoors Step-by-Step

When the day finally arrives to put your begonias in the ground or their final outdoor pots, follow these simple steps for the best results.

Planting in the Garden

1. Loosen the Soil: Use a trowel to loosen the soil about 6 to 8 inches deep. This makes it easier for new roots to spread out.
2. Dig a Shallow Hole: For a tuber that hasn't been started indoors, the hole only needs to be about 1 to 2 inches deep. If you are transplanting a started plant, dig a hole as deep as the root ball.
3. Placement: Place the tuber or plant in the hole. Ensure the top of the tuber or the base of the plant's stem is just barely covered by soil. Planting too deep can lead to stem rot.
4. Spacing: Space your begonias about 8 to 12 inches apart. This allows for good air circulation, which helps prevent powdery mildew (a common white fungus that can grow on leaves). The Begonia Upright Double Roseform Pink is a reliable choice for a shady bed.

Planting in Containers

1. Select the Right Pot: Ensure your pot has at least one large drainage hole in the bottom.
2. Use Fresh Soil: Always use fresh potting mix for the new season. Old soil can harbor pests or diseases and lacks the nutrients your plants need.
3. Water to Settle: After planting, water the soil gently. This helps settle the dirt around the roots and removes any large air pockets. The Begonia Upright Double Superba White works especially well in containers.

Key Takeaway: Keep begonias near the surface of the soil. Depth and spacing are the quiet winners when it comes to healthy, rot-free plants.

Watering and Feeding for Maximum Blooms

Once your begonias are settled outside, your main job is to keep them comfortable. Because they bloom continuously for months, they use a lot of energy.

Water Correctly, Not Constantly

The most common mistake with begonias is watering too often. Instead of giving them a little bit of water every day, try the "deep soak" method.

• Check the Soil: Stick your finger an inch into the soil. If it feels dry, it is time to water. If it feels damp, wait another day.
• Water the Base: Try to keep water off the leaves and flowers. Watering at the base of the plant helps prevent leaf spots and fungal issues.
• Container Care: Pots dry out much faster than the ground. In the heat of midsummer, you may need to check your containers every day.

Feeding Your Plants

Think of fertilizer as "fuel" for your flowers. Begonias are "heavy feeders," meaning they need regular nutrients to keep producing those big blooms.

• Early Season: When the plant is mostly growing leaves, a balanced, water-soluble fertilizer works well.
• Blooming Season: Once you see flower buds appearing, switch to a fertilizer with a slightly higher middle number (phosphorus), which encourages more blooms.
• Frequency: Most gardeners find success by fertilizing every two weeks at half-strength. This provides a steady stream of food without overwhelming the plant.

Caring for Begonias at the End of the Season

As the summer fades and the nights begin to cool, your begonias will start to slow down. Because they are not hardy in most of the U.S., you have two choices: let them go or save them for next year.

Treating Them as Annuals

Many gardeners choose to treat begonias as annuals. Once the first light frost hits the foliage, the leaves will turn black and the plant will wilt. At this point, you can simply pull the plants up and add them to your compost pile.

Saving the Tubers

If you have a variety you particularly love, you can save the tubers to replant next spring. Longfield Gardens backs healthy starts with a 100% Quality Guarantee.

1. Reduce Water: In late September, stop watering the plants. This encourages the plant to go dormant.
2. Dig Them Up: Before the first hard freeze, carefully dig up the tubers. Keep the stems attached for now.
3. Dry Them: Place the tubers in a dry, frost-free place for about two weeks. Once the stems are dry and shriveled, they should easily snap off the tuber.
4. Store for Winter: Store the clean, dry tubers in a box of peat moss or sawdust in a cool, dark place (around 40-50°F). A basement or crawlspace is often perfect.

Common Questions About Planting Timing

Even with a plan, gardening often brings up specific "what if" scenarios. Here is how to handle a few common timing challenges.

What if I plant too early and a frost is predicted?

If your begonias are already in the ground and a surprise late frost is in the forecast, don't panic. You can protect them by covering them with a frost blanket, an old bedsheet, or even an upside-down plastic bucket overnight. Just be sure to remove the cover as soon as the sun comes up the next morning so the plants don't overheat.

Can I leave my begonias in the pots over winter?

If you live in Zone 9 or warmer, yes. If you live in a colder zone, the soil in a pot will freeze much faster than the ground. This will kill the tuber. If you want to keep them, you must bring the pots into a frost-free area like a garage or basement where the temperature stays above freezing.

My tubers aren't sprouting yet—is it too late?

Begonias can be slow to wake up! Sometimes it takes 3 to 4 weeks for the first nubs to appear. If your tubers are firm to the touch (like a fresh potato), they are likely just fine. Ensure they are in a warm spot (70°F) to help speed things along. If they are soft or mushy, that is a sign of rot, and they will not grow.

Conclusion

When it comes to the question of when to plant begonia outside, the answer is always tied to the warmth of the air and the soil. By waiting for those consistent 50°F nights and 60°F soil, you are giving your plants the best possible environment to flourish. Whether you start them early indoors to get a head start or wait for the natural warmth of late spring, the rewards are well worth the patience.

At Longfield Gardens, we believe that gardening should be an enjoyable, rewarding experience for everyone. By following these simple rules of timing, temperature, and placement, you can transform the shady parts of your yard into a colorful retreat. Begonias are some of the most generous plants in the garden, offering nonstop beauty from the moment they are planted until the very end of the season.

• Wait for the soil to reach 60°F and nights to stay above 50°F.
• Start tubers indoors 8-12 weeks early for a longer blooming season.
• Take one week to "harden off" plants before moving them outside permanently.
• Choose a location with filtered morning sun and excellent drainage.

Gardening is about working with nature’s timeline. When you give begonias the warmth they crave, they will thank you with a spectacular display of color all summer long.

FAQ

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

A healthy begonia tuber should feel firm and heavy, much like a fresh potato or a ginger root. If you see small pink or white "eyes" or nubs on the hollow side, the plant is already starting to wake up. If the tuber feels light, hollow, or squishy when you press on it, it has likely dried out or rotted and will not grow.

Can I plant begonia tubers directly in the ground without starting them indoors?

Yes, you can certainly plant tubers directly in the garden, provided the soil is warm (at least 60°F) and all danger of frost has passed. While the plants will bloom later in the summer than those started indoors, they will still provide a beautiful show. In warmer southern zones, direct planting is the standard method.

Why are my begonia leaves turning yellow after I planted them outside?

Yellowing leaves shortly after planting is usually a sign of one of two things: transplant shock or overwatering. If the weather recently took a cold dip, the plant might be reacting to the temperature change. However, the most common cause is soil that is too wet. Ensure you are letting the top inch of soil dry out between waterings.

Does the variety of begonia change when I should plant it?

The timing remains the same for all types—tuberous, wax, and rex begonias all require warm temperatures to thrive. However, wax begonias are slightly more resilient and can sometimes handle a bit more sun and wind during the hardening-off process. Tuberous begonias, especially the large-flowered varieties, are the most sensitive to cold and should be the last ones moved outside.