Table of Contents
- Introduction
- Understanding Begonia Temperature Sensitivity
- The Golden Rule: Wait for the Last Frost
- Soil Temperature Matters More Than Air
- Regional Timing Across the United States
- Starting Begonias Indoors to Extend the Season
- Hardening Off: The Bridge to the Outdoors
- Choosing the Right Spot for Timing Success
- Planting Depth and Spacing
- Summer Care: Keeping the Momentum Going
- Fall Timing: When to Move Them Back In
- Conclusion
- FAQ
Introduction
There is something truly special about the moment your shade garden begins to glow with the vibrant, jewel-toned colors of begonias. Whether you are tucking tuberous begonias into hanging baskets or lining a walkway with cheerful wax begonias, these plants are the champions of the summer shade. At Longfield Gardens, we love how begonias provide nonstop color from the early days of summer all the way until the first frost of autumn.
Knowing when to plant begonias outside is the most important step in ensuring a season full of lush foliage and heavy blooms. Because these are tropical plants by nature, they thrive in warmth and can be sensitive to the lingering chill of early spring. Getting the timing right allows the plants to establish strong roots and healthy stems before the heat of summer arrives.
This guide is designed to help home gardeners across the country identify the perfect window for moving their begonias outdoors. We will cover temperature requirements, regional timing, and the simple steps you can take to prepare your plants for life in the garden. By following a few basic rules of timing and care, you can enjoy a spectacular display that lasts for months.
Key Takeaway: Success with begonias starts with patience; waiting for consistently warm soil and air temperatures ensures your plants thrive rather than just survive.
Understanding Begonia Temperature Sensitivity
To understand when to plant begonias outside, it helps to know a bit about where they come from. Most begonias are native to tropical and subtropical regions in Central and South America, Asia, and Africa. In these climates, frost is non-existent and temperatures remain warm year-round. This means begonias have not evolved to handle freezing temperatures or even the "damp chill" common in many parts of the U.S. during early spring.
The most common types of begonias for home gardens include tuberous, wax, and rex varieties. While they have different growth habits, they all share a common need for warmth. If planted too early, the cold soil can cause the tubers to sit dormant or, in worse cases, begin to rot. Cold air can also stunt the growth of the leaves, leading to a slow start to the blooming season.
Think of begonias as "warm-season" plants, much like tomatoes or peppers. They perform best when the environment mimics their tropical origins. When you wait for the right conditions, you are giving the plant the signal that it is safe to put energy into growing leaves and flowers.
The Golden Rule: Wait for the Last Frost
The most important rule for planting begonias outside is to wait until all danger of frost has passed. Even a light frost can turn begonia leaves into mush and damage the tender growing points of the plant. Depending on where you live, this window can vary by several months.
In the southern United States, the last frost may occur in February or March. In the northern states or at higher elevations, gardeners might need to wait until late May or even early June. It is always better to wait an extra week than to rush and lose your plants to an unexpected cold snap.
You can find your local "average last frost date" through online resources or by contacting a local university extension office. However, keep in mind that these dates are just averages. Always check the long-range weather forecast before moving your plants. Look for a stretch of at least ten days with no freezing temperatures in sight.
Monitoring Nighttime Temperatures
While the absence of frost is the first hurdle, nighttime temperatures are equally important. Begonias prefer nights that are consistently 50°F or warmer. If the nights are still dipping into the 40s, the plants may survive, but they will likely sit still without growing.
For the fastest growth and the most blooms, aim for nighttime temperatures that stay around 60°F. This consistent warmth encourages the plant to maintain an active metabolism. If you have already moved your pots outside and a cold night is predicted, it is a good idea to bring them into a garage or cover them with a light cloth to hold in the day's heat.
What to Do Next
- Check your local Hardiness Zone Map to understand your general climate.
- Find your average last frost date as a baseline.
- Monitor your local 10-day forecast for nighttime lows consistently above 50°F.
- Prepare a temporary shelter or space in the garage just in case of a late-season chill.
Soil Temperature Matters More Than Air
It is a common mistake to think that because the air feels warm, the garden is ready for planting. Soil temperature actually plays a bigger role in the health of your begonias. Soil holds onto the cold much longer than the air does. If you tuck a begonia tuber into soil that is 45°F, it will essentially stay in a state of "suspended animation."
Ideally, the soil should be at least 60°F before you plant begonias directly in the ground. You can check this with a simple soil thermometer or by observing other plants in your neighborhood. When you see trees fully leafed out and other warm-season flowers beginning to grow, the soil is likely warm enough.
If you are planting in containers, you have a bit more flexibility. Soil in pots and hanging baskets warms up much faster than the ground, and Hanging Begonias can often be moved outside a week or two earlier than ground-planted begonias, provided the air temperature is safe.
Key Takeaway: Soil acts like a thermal blanket; wait until it reaches 60°F to ensure your begonia roots can begin absorbing nutrients and moisture immediately.
Regional Timing Across the United States
Because the U.S. spans so many different climates, "spring" means different things to different gardeners. Here is a general guide for when to plan your begonia planting based on your region:
The Southern United States (Zones 8-11)
In these warmer regions, you can often plant begonias outside in March or April. Since begonias are hardy in zones 9-11, some varieties may even survive the winter if the ground doesn't freeze. However, keep an eye on the sun. As the season progresses, the intense southern sun can be too much for some varieties, so early planting helps them establish before the peak heat of July.
The Central United States (Zones 6-7)
Gardeners in the Midwest and Mid-Atlantic typically look toward mid-to-late May. Mother’s Day is a common benchmark for many, but always verify the forecast. If the spring has been particularly rainy and cool, waiting until the end of May often yields better results.
The Northern United States and High Altitudes (Zones 3-5)
In the North, patience is a virtue. It is common to wait until early June to move begonias outside. Because the growing season is shorter here, many gardeners choose to start their begonias indoors (more on that below) so the plants are already blooming by the time they hit the garden.
Starting Begonias Indoors to Extend the Season
One of the best ways to get a head start on the season is to start your begonia tubers indoors. This allows you to bypass the cold soil of early spring and have well-established plants ready the moment the weather breaks. We recommend starting tuberous begonias indoors about 8 to 12 weeks before your last frost date.
To start them, fill a shallow tray or small pots with a light, well-draining potting mix. Place the tubers with the indented (concave) side facing up. This is where the new sprouts will emerge. Just barely cover the tubers with soil—about half an inch to an inch is plenty.
Keep the pots in a warm spot with bright, indirect light. A windowsill that doesn't get direct, scorching sun is perfect. Water sparingly at first; you want the soil to be moist like a wrung-out sponge, but never soggy. In a few weeks, you will see pink or green nubs beginning to sprout. By the time the outdoor temperatures are safe, you will have a sturdy plant ready to go.
The Benefits of Pre-Sprouting
- Earlier Blooms: Begonia Non Stop Mix - Bulk Offer can help you enjoy flowers in late June rather than waiting until August.
- Stronger Plants: Begonias started indoors are less likely to be overwhelmed by weeds or heavy spring rains.
- Better Success Rates: You can monitor the tubers closely during the critical sprouting phase.
Hardening Off: The Bridge to the Outdoors
You shouldn't move begonias directly from a cozy indoor environment to the garden all at once. The transition can be a shock to their system. "Hardening off" is the process of gradually acclimating your plants to the outdoor elements, including wind, fluctuating temperatures, and stronger light.
Start this process about 7 to 10 days before you plan to plant them permanently. On the first day, place your begonias in a shaded, protected spot for just two or three hours, then bring them back inside. Each day, leave them out a little longer and gradually expose them to a bit more light.
By the end of the week, the plants will have toughened their leaf cuticles and strengthened their stems. This simple step prevents "transplant shock," which can cause leaves to drop or turn white from sunscald. If you purchased your begonias from a greenhouse or garden center, they likely still need a few days of hardening off, as they have been living in a very controlled environment.
A Typical Hardening Off Schedule
- Day 1-2: 2 hours in full shade, protected from wind.
- Day 3-4: 4-5 hours in filtered light.
- Day 5-6: All day in their intended garden spot; bring in at night.
- Day 7: Leave out overnight if temperatures stay above 50°F.
Choosing the Right Spot for Timing Success
Where you plant your begonias also influences when they will start to thrive. Matching the plant to the right location ensures that once they are outside, they stay healthy.
Light Requirements
Most begonias prefer partial shade to full shade. Tuberous begonias, in particular, love filtered light, such as what you might find under a tall tree. If you plant them in a spot that gets too much hot afternoon sun, the leaves may scorch, regardless of how perfect your timing was. Wax begonias are a bit more versatile and can often handle more sun, especially in northern climates, and Begonia Upright Double Bertini is one of the sun-tolerant options.
Soil and Drainage
"Drainage" is a word gardeners use to describe how quickly water moves through the soil. Begonias have fleshy stems and tubers that store water, which makes them very sensitive to "wet feet." If the soil stays soggy, the plants can struggle with rot.
Before planting, check your soil by digging a small hole and filling it with water. If it drains away within an hour, you have good drainage. If it sits for a long time, consider adding compost or peat moss to loosen the soil, or better yet, plant your begonias in raised beds or containers where you can control the soil quality.
What to Do Next
- Observe your garden at different times of day to see where the shadows fall.
- Check for low spots in the yard where water pools after rain.
- Purchase a high-quality potting mix if you are using containers.
- Plan your spacing—usually 8 to 12 inches apart—to allow for good airflow between plants.
Planting Depth and Spacing
Once the timing is right and your spot is picked, the actual planting is quite simple. How to Plant Tuberous Begonias: Which End Is Up? is a helpful walkthrough for getting the depth right—it’s a small detail that makes a big difference.
For tuberous begonias, plant the tubers about 1 inch deep. If you are transplanting a begonia that you started in a pot, set it in the ground so the top of the root ball is level with the surrounding soil. Planting too deep can lead to stem rot, while planting too shallow can cause the plant to dry out too quickly or tip over as it grows taller.
Spacing is also important for health. Begonias enjoy good air circulation, which helps prevent powdery mildew and other fungal issues. Generally, space smaller wax begonias about 6 to 8 inches apart. For larger tuberous varieties, 10 to 12 inches is usually ideal. If you are planting in a hanging basket, you can tuck them slightly closer together for a "full" look, but be sure not to overcrowd them.
Summer Care: Keeping the Momentum Going
Once your begonias are settled in their outdoor home, they are relatively low-maintenance. The goal is to provide consistent conditions that mimic their tropical home.
Watering Correctly
Watering is less about a strict schedule and more about observing the soil. The "deep, then let it dry" method works best. Stick your finger into the soil; if the top inch feels dry, it is time to water. Try to water at the base of the plant rather than over the leaves. This keeps the foliage dry and reduces the chance of disease.
Fertilizing for Blooms
Begonias are heavy feeders because they produce so many flowers over a long season. Using a balanced, water-soluble fertilizer every two to three weeks will give them the nutrients they need to keep blooming. Look for a fertilizer with a slightly higher middle number (phosphorus) to encourage flower production. If you want a classic pink-and-white display, Begonia Upright Double Superba Pink & White is a container-friendly option.
Safety Note
It is important to remember that many garden plants, including begonias, can be toxic if eaten by pets or small children. Are Begonia Plants Poisonous to Dogs? Safety Tips & Facts explains what to know before planting them near curious pets. They contain calcium oxalates, which can cause irritation in the mouth and throat. It is always a good idea to plant them in areas where pets won't be tempted to snack on them and to keep any stored tubers out of reach.
Fall Timing: When to Move Them Back In
Just as spring timing is about waiting for the heat, fall timing is about watching for the cold. Begonias will continue to bloom beautifully until the temperatures begin to drop. When night temperatures start to consistently fall below 50°F, you will notice the plants start to slow down.
If you live in a cold climate and want to save your tuberous begonias for next year, you need to act before the first hard frost. A light frost may blacken the leaves, which is actually a signal to the plant to go dormant. At this point, you can dig up the tubers, trim off the stems, and let the tubers dry in a cool, dark place for a few days. Once dry, store them in a box with peat moss or sawdust in a spot that stays around 50°F, such as a cool basement.
Wax begonias are usually treated as annuals, but they can actually be brought inside and kept as houseplants over the winter! Simply pot them up and move them to a bright window before the first frost hits.
Conclusion
Mastering when to plant begonias outside is one of the most rewarding skills a gardener can develop. By respecting the plant's tropical nature and waiting for the soil and air to warm up, you set the stage for a spectacular summer display. Whether you are filling a shady corner or brightening up your front porch with hanging baskets, begonias offer a reliable and beautiful return on your investment of time and care.
Remember to watch your local weather patterns, be patient with the spring thaw, and give your plants a slow introduction to the outdoors. With these simple steps, your garden will be a lush, colorful retreat all season long. We are here to support your journey, and our 100% Quality Guarantee reflects that promise.
- Wait for nighttime temperatures to stay above 50°F consistently.
- Ensure soil temperatures have reached at least 60°F before planting in the ground.
- Use the hardening-off process to prevent transplant shock.
- Prioritize drainage and partial shade for the healthiest growth.
Next Step: Check your local frost dates today and start planning your shade garden layout. When you're ready to start, we provide premium begonia tubers to help you achieve the garden of your dreams.
FAQ
Can I plant begonias outside if it might still rain a lot?
Rain is generally fine for begonias as long as your soil has excellent drainage. However, if your garden soil stays soggy or forms puddles after a heavy rain, it is better to wait until the soil dries out a bit or plant them in containers. Excessively wet, cold soil in early spring is the leading cause of tuber rot. A trailing variety like Begonia Hanging Pink Balcony can be a good way to keep flowers elevated.
What happens if I plant my begonias outside too early?
If begonias are exposed to temperatures below 40°F, they may suffer from "chilling injury." This often looks like blackened or translucent spots on the leaves. If a frost occurs, the plant may die back to the ground. Even if the plant survives, being too cold early on can stunt its growth for the rest of the summer.
Do different types of begonias have different planting times?
While all begonias love warmth, wax begonias are often a bit sturdier and can be moved outside slightly earlier than the more delicate tuberous or rex varieties. However, for the best results across all types, sticking to the "after the last frost" rule is the safest and most effective approach for any home gardener.
Can I plant begonias in full sun if I plant them early in the season?
Planting early doesn't change a plant's light requirements. While the early spring sun is less intense, begonias—especially tuberous varieties—will still struggle once the summer heat arrives. It is best to plant them in their ideal "right place" (partial to full shade) from the very beginning to avoid having to move them later.