Introduction
There is a special kind of excitement that comes with the arrival of spring. As the days grow longer, gardeners everywhere look forward to filling their pots and garden beds with vibrant color. Begonias are a favorite for this very reason, offering lush foliage and brilliant blooms that last from summer through the first frost. At Longfield Gardens, we want to help you enjoy these stunning plants at their absolute best.
Knowing exactly when to move your begonias outdoors is the most important step in ensuring their success. These plants are tropical by nature, which means they thrive in warmth and are sensitive to the cold. While it can be tempting to plant as soon as the sun comes out, a little patience goes a long way in protecting your plants.
This guide will help you identify the perfect window for planting begonias outside. Whether you are working with wax begonias, tuberous varieties, or the striking Rex begonia, we will cover the temperature thresholds and environmental signs to look for. By following a few simple rules, you can ensure your begonias transition smoothly to their summer home.
The Tropical Heritage of Begonias
To understand the timing for planting, it helps to know where begonias come from. Most varieties we enjoy in our American gardens are native to the tropical and subtropical regions of Central and South America, Africa, and Asia. In these climates, there is no such thing as frost, and temperatures rarely dip into the low 50s.
Because of this heritage, begonias are not "hardy" in most of the United States. They are classified as tender perennials or annuals depending on your location. They have a high water content in their stems and leaves, which makes them very susceptible to damage from cold air and soil.
When a begonia is exposed to temperatures that are too low, it doesn't just stop growing—it can actually suffer physical damage. The cells in the leaves can rupture, leading to blackened foliage or mushy stems. This is why we emphasize waiting for consistent warmth rather than just the absence of snow.
The Golden Rule: Nighttime Temperatures
The most reliable indicator for when to plant begonias outside is the consistent nighttime temperature. While a sunny 70-degree day in April might feel like summer, the soil and the nighttime air often tell a different story.
For most begonias, the magic number to remember is 50°F. You should wait to move your plants outside until the thermometer stays above 50°F every single night. If you are growing tuberous begonias, which are particularly sensitive, many gardeners prefer to wait until nighttime lows are consistently 60°F.
Planting too early can result in "stunting." This happens when the plant is chilled, causing it to sit dormant for weeks, even after the weather warms up. A plant that is put out two weeks later in warmer soil will often outgrow a plant that was put out early and suffered through a cold snap.
Key Takeaway: Always prioritize nighttime lows over daytime highs. Begonias need a stable environment with air temperatures consistently above 50°F to thrive without stress.
Understanding Soil Temperature
While we often check the air temperature, the temperature of the soil is just as important for root health. Begonia roots are delicate and do not like to sit in cold, damp earth. If the soil is too cold, the roots cannot effectively take up water and nutrients, which leads to yellowing leaves and poor growth.
Soil warms up much more slowly than the air. Even if the air feels warm, the ground may still be holding onto the chill of winter. This is especially true for garden beds. Containers and hanging baskets tend to warm up faster because they are elevated and surrounded by air.
If you want to be precise, you can use a simple soil thermometer. For begonias, you are looking for a soil temperature of at least 60°F. If the soil is still cool to the touch, it is better to keep your plants in a protected area like a porch or a greenhouse for a little while longer.
The Role of the Last Frost Date
The "average last frost date" is a term you will hear often in gardening circles. This is the date in the spring when there is a 50% chance that a frost will no longer occur. It is a helpful starting point, but it should not be your only guide.
For begonias, the last frost date is the absolute earliest you should even consider planting. However, because begonias are tropical, they usually need an extra two to three weeks of "cushion" beyond that date. For help finding your location’s timing, check Longfield Gardens’ hardiness zone map.
- Zones 9-11: In these warm climates, you may be able to plant as early as March or April.
- Zones 6-8: Mid-to-late May is often the safest window.
- Zones 3-5: Early June is frequently the best time to ensure the soil and air are warm enough.
Every year is different. Some springs arrive early, while others linger with cold rains. Always check your local 10-day forecast before making the move. If there is a "cold front" predicted with temperatures dipping into the 40s, wait until it passes.
Starting Begonias Indoors for an Early Start
One of the best ways to enjoy blooms sooner is to start your begonias indoors. This is particularly common with tuberous begonias. Because these varieties take several months to reach full blooming size, starting them in the safety of your home gives them a significant head start.
We recommend starting begonia tubers about 8 to 12 weeks before you plan to move them outside. This usually means planting them in small pots indoors during late February or March. By the time the outdoor temperatures are safe, you will have a sturdy, well-established plant ready to go.
When starting indoors:
- Use a high-quality potting mix that drains well.
- Keep the pots in a warm spot with bright, indirect light.
- Water sparingly at first—just enough to keep the soil slightly damp.
- Wait for sprouts to appear before increasing water.
Starting indoors doesn't mean the plants can go out earlier. It simply means that when the weather finally is right, your plants will be much further along in their growth cycle.
How to Transition Begonias Outdoors (Hardening Off)
You should never move a begonia directly from a warm house or a cozy greenhouse into the garden. The sudden change in light intensity, wind, and temperature fluctuations can shock the plant. This transition process is called "hardening off."
Hardening off allows the plant to gradually toughen its leaf cuticles and adjust to the outdoor environment. This process should take about 7 to 10 days.
For a more detailed walkthrough, see Longfield Gardens’ begonia hardening off guide.
The Hardening Off Schedule
- Days 1-2: Place your begonias in a fully shaded, protected spot (like a covered porch) for just 2 or 3 hours during the warmest part of the day. Bring them back inside for the night.
- Days 3-4: Increase the time to 5 or 6 hours. Continue to keep them in the shade and bring them in at night.
- Days 5-6: Leave the plants out all day. Introduce them to a small amount of morning sunlight if they are a sun-tolerant variety. If the nighttime temperatures are staying above 55°F, you can leave them out overnight in a protected spot.
- Days 7-10: Keep the plants out 24/7. Gradually move them to their permanent location.
What to do next:
- Check the 10-day forecast for any surprise cold snaps.
- Find a shaded spot near your door to make moving the pots easy.
- Observe the leaves for any signs of "sunburn" (white or bleached spots) and move them back to shade if needed.
Choosing the Right Planting Site
Once the timing is right and your plants are hardened off, you need to choose the best spot in your yard. "Right plant, right place" is one of our favorite rules at Longfield Gardens because it makes gardening so much easier.
Hanging begonias are especially useful if you want to brighten a porch or patio with cascading color.
Light Requirements
Most begonias prefer partial shade. They love bright, indirect light but can struggle in the intense, direct heat of the afternoon sun.
- Wax Begonias: These are the most sun-tolerant and can often handle more direct light, especially in northern climates.
- Tuberous Begonias: These prefer dappled light or morning sun with afternoon shade.
- Rex Begonias: These are grown for their foliage and generally prefer deep to moderate shade.
Soil and Drainage
Begonias have fine, shallow roots that can rot if they stay too wet. "Drainage" is a fancy way of saying how quickly water moves through the soil. You want soil that holds some moisture but lets the excess run away freely.
- If planting in the ground, add compost or aged bark to loosen heavy clay soil.
- If planting in containers, ensure there are plenty of drainage holes at the bottom.
- Avoid spots where water puddles after a rainstorm.
Variety-Specific Timing Considerations
While the "50-degree rule" applies to most begonias, different types have slightly different preferences. Recognizing which type you have will help you fine-tune your schedule.
Wax Begonias (Semperflorens)
These are the hardy workhorses of the begonia world. They have waxy green or bronze leaves and small clusters of red, pink, or white flowers. They are generally the first begonias you can move outside because they handle slightly cooler temperatures better than their cousins. Once the threat of frost is gone and nights are consistently 50°F, these are ready to go.
Tuberous Begonias
These varieties produce massive, rose-like blooms and are often found in hanging baskets (like the "pendula" types) or upright containers. Because they grow from a fleshy tuber, they are very sensitive to rot in cold, wet soil. It is best to be extra patient with these. Wait until the air is truly balmy—nights around 60°F are ideal.
For a deeper look at this group, browse Non Stop Begonias and Upright Double Begonias.
Cane-Like Begonias (Angel Wing)
Cane begonias have long, upright stems and beautiful, wing-shaped leaves often marked with silver spots. These are frequently kept as houseplants but can spend the summer outdoors. Because they are often quite large, they can be catch the wind easily. Move these out only after the weather is settled and the winds have calmed.
Rex Begonias
Grown for their incredible leaf patterns and colors, Rex begonias are perhaps the most sensitive to humidity and temperature. They thrive in the "dog days" of summer when it is warm and humid. If your spring is particularly dry and windy, keep these inside a bit longer to prevent the edges of the leaves from drying out.
Monitoring the Weather After Planting
Gardening involves a bit of observation. Even after you have planted your begonias, keep an eye on the weather. Spring weather can be unpredictable, and a late-season cold snap can happen.
If a surprise frost or a night in the low 40s is predicted:
- For containers: Simply move them back into the garage or house for the night.
- For garden beds: Cover the plants with a frost blanket or even an old bedsheet. Avoid using plastic directly touching the leaves, as it can transfer the cold.
- Watering: If a cold night is coming, make sure the plants are hydrated. Moist soil holds more heat than dry soil, providing a tiny bit of extra protection for the roots.
Remember that gardening is a partnership with nature. Some years the begonias will go out on Mother's Day, and other years you might be waiting until the first week of June. Following the lead of the weather ensures your plants stay healthy and stress-free.
For shipping timing based on your zone, see Longfield Gardens’ shipping information.
Signs Your Garden is Ready
If you don't want to rely solely on the thermometer, nature provides its own clues. Phenology is the study of cyclic biological events, like when certain trees leaf out or birds migrate. These events can often tell you more about the "readiness" of your garden than a calendar date.
In many regions, a good sign that it is safe to plant tender annuals like begonias is when the lilacs have finished blooming and the peonies are starting to open. At this stage, the soil has usually absorbed enough spring sunshine to stay warm through the night.
Another sign is the emergence of local "heat-loving" weeds or grasses. When you see the lawn really starting to grow vigorously and needing frequent mowing, it is a sign that the ground temperature has reached the levels begonias enjoy.
For more general planning tools and seasonal references, visit Longfield Gardens’ Learn center.
The Reward of Waiting
It can be hard to wait when the garden centers are full of blooming plants. However, the reward of waiting for the right window is a begonia that takes off and grows rapidly. A plant put into warm soil will quickly develop a strong root system, leading to more flowers and better heat tolerance later in the summer.
At Longfield Gardens, we have seen that the most successful gardens are built on these simple basics. By matching your planting time to the plant's needs, you reduce the risk of disease and pests, which often attack stressed plants. A happy, warm begonia is a beautiful begonia.
If you want more color for warm-season containers, explore Begonia Flower Bulbs for Sale and Begonia Hanging Golden Balcony.
Key Takeaway: Patience in the spring pays off in the summer. Waiting for 50-60°F nighttime temperatures ensures your begonias spend their energy blooming rather than recovering from cold shock.
Summary of Begonia Planting Steps
- Check your zones: Identify your last frost date and add 2–3 weeks.
- Watch the lows: Wait for consistent nighttime temperatures of 50°F (60°F for tuberous types).
- Test the soil: Ensure the ground feels warm to the touch and isn't waterlogged.
- Start the transition: Spend 7–10 days hardening off your plants to outdoor light and air.
- Pick the spot: Choose a location with well-draining soil and protection from harsh afternoon sun.
- Have a backup plan: Keep a frost cloth or space in the garage ready for unexpected cold nights.
Conclusion
Planting begonias outside is one of the most rewarding ways to transition your garden into the summer season. By waiting for the right temperature and properly hardening off your plants, you set the stage for months of nonstop color and beautiful foliage. Remember that gardening is meant to be an enjoyable and relaxing activity. There is no need to rush; the sun and warmth will eventually arrive, and your begonias will be ready to shine.
- Wait for consistent nighttime temperatures above 50°F.
- Acclimatize plants slowly through the hardening off process.
- Ensure soil is well-draining to protect delicate roots.
We invite you to explore our selection of premium begonias and other summer-blooming bulbs at Longfield Gardens to find the perfect varieties for your shady spots and containers. With the right timing and a little care, your garden will be a vibrant sanctuary all season long.
Success with begonias is all about the "warmth." When the nights feel like summer, your begonias are ready to move out and grow.
FAQ
What happens if I plant my begonias too early?
If begonias are planted while the soil or air is still cold, they can experience "chill shock." This may cause the leaves to turn yellow or black, and the plant may stop growing entirely for several weeks. In severe cases, a late frost can kill the plant by rupturing its water-filled stems.
Can begonias stay outside if it rains a lot in the spring?
While begonias love moisture, they do not like "wet feet." If your spring is exceptionally rainy and your garden soil does not drain well, it is best to keep begonias in pots in a protected area. Excessive rain in cold soil is a primary cause of tuber and root rot.
Do I need to bring my begonias inside every night?
Only during the hardening off period or if a surprise cold snap is predicted. Once the nighttime temperatures are consistently above 50-55°F, begonias are perfectly happy staying outdoors 24/7. Monitoring the weather forecast for the first few weeks after planting is always a smart habit.
How do I know if my begonia is sun-scalded after moving it outside?
Sun-scald usually appears as white, papery, or bleached spots on the leaves. This happens when a plant is moved from a low-light indoor environment to bright outdoor light too quickly. If you see this, move the plant back into a more shaded area and slow down the hardening off process.
