Introduction
Tuberous begonias are the gems of the shade garden. Their lush, rose-like flowers and dramatic foliage bring high-end elegance to hanging baskets and garden beds alike. If you have been looking for a way to add a splash of tropical color to a quiet corner of your yard, begonias are an excellent choice. At Longfield Gardens, we enjoy watching these spectacular plants transform from humble, potato-like tubers into a sea of vibrant blossoms.
Timing is the most important factor when it's time to start your begonia journey. Because these plants are native to warm, tropical climates, they are quite sensitive to the cold. Getting the timing right ensures your plants grow strong and bloom from mid-summer all the way until the first frost. This article will help you determine the perfect window for planting based on your local weather and your goals for the season.
Whether you want to get a head start by starting your tubers indoors or you prefer to wait for the warm summer sun, we have you covered. We will look at how to read your local climate and how to prepare your tubers for a long, beautiful season. Following a few simple timing rules will lead to a garden full of stunning, effortless color.
The Short Answer: Spring is the Season
The most straightforward answer to when to plant begonia bulbs is during the spring. However, "spring" looks different depending on where you live. Begonias are not fans of the cold, so the calendar date is less important than the temperature of the air and the soil.
For most gardeners in the United States, the window for planting begins as early as February for indoor starting and as late as June for outdoor planting. The key is to wait until the threat of frost has completely passed before your plants spend any time outside.
Begonias need a long growing season to reach their full potential. They take their time to "wake up" and begin growing. Because of this, many gardeners choose to start them indoors several weeks before the weather warms up. This extra time allows the plant to develop a strong root system and early leaves, leading to flowers much sooner in the summer.
Key Takeaway: The best time to plant begonia tubers is 8 to 12 weeks before the last expected frost if starting indoors, or once the soil has warmed to at least 60°F for outdoor planting.
Why Timing Matters for Begonias
Begonias are unique because they grow from tubers, which are thickened underground stems. These tubers hold all the energy the plant needs to start its life. However, this energy remains dormant until the conditions are just right.
If you plant too early in cold, wet soil, the tuber may simply sit there without growing. In some cases, cold and damp conditions can cause the tuber to struggle. On the other hand, if you plant too late in the summer, you might miss out on several weeks of beautiful blooms.
Understanding the "Wake-Up" Period
Begonia tubers have a natural internal clock. After a winter of rest, they need a combination of warmth and light to signal that it is time to grow. This process is often called "waking up" the tubers.
By timing your planting correctly, you align with the plant’s natural cycle. When the tuber feels the consistent warmth of spring, it begins to push out small, pinkish buds called "eyes." These eyes eventually become the stems and leaves of your plant.
The Role of Temperature
Temperature is the primary guide for begonia timing. These plants thrive when the air is between 60°F and 75°F. They are particularly sensitive to nighttime temperatures. Even if your days are warm, a chilly night below 50°F can slow down their growth.
Before moving any begonias outside, it is a good idea to check your local weather forecast and hardiness zone map. Look for a stretch of nights where the temperature stays consistently above 50°F. This is the green light that your begonias will be safe and happy in their outdoor home.
Starting Begonias Indoors for Earlier Blooms
If you want to see flowers in early July rather than late August, starting your tubers indoors is the way to go. This is a popular method because it extends the enjoyment of the plant.
The 8-to-12-Week Rule
The general rule of thumb is to start your tubers indoors about 8 to 12 weeks before your area’s average last frost date. For many people in the middle of the country, this means planting in March or early April. If you live in a northern state with a short summer, starting in late February or early March gives your begonias the head start they need to put on a show.
How to Start Indoors
Starting begonias indoors is a rewarding late-winter project. You do not need a professional greenhouse to be successful. A warm room and a bright windowsill are usually enough to get things moving.
- Check for Sprouts: Take your tubers out of their packaging and look for the indented side. This is the top. If you see tiny pink or white nubs, your begonias are already waking up.
- Use Shallow Containers: You can start tubers in small pots or even a shallow tray.
- Provide Warmth: Begonias like it warm. A spot near a radiator (but not on it) or a room that stays around 70°F is perfect.
- Wait for Light: You do not need much light until the first leaves appear. Once you see green growth, move them to a bright spot with indirect sunlight.
What to Do Next: Indoor Care
- Keep the soil lightly moist, like a wrung-out sponge.
- Avoid overwatering before the sprouts appear, as the tuber doesn't have roots to drink the water yet.
- Watch for the first leaves to unfurl, which is an exciting sign of progress.
Planting Directly Outdoors
While starting indoors is great, it is not a requirement. You can plant begonia tubers directly into your garden beds or outdoor containers once the weather is warm enough.
Checking the Soil Temperature
The soil temperature is often more important than the air temperature for direct planting. You want the soil to feel warm to the touch, usually around 60°F. If the soil is still cold and clammy from spring rains, wait another week or two.
In many regions, the best time for direct outdoor planting is late May or early June. This is usually the same time you would plant other warm-weather favorites like tomatoes or zinnias.
Choosing the Right Spot
When the timing is right to go outside, location is your next priority. Begonias are famous for their love of shade. They do best in a spot that receives "dappled" sunlight or morning sun followed by afternoon shade.
For more shade-friendly ideas, browse our Spring-Planted Bulbs for Shade. Direct, hot afternoon sun can be a bit much for their delicate petals and leaves. If you find a spot where you would enjoy sitting with a book on a hot day, your begonias will likely love it there, too.
Pro Tip: If you are planting in a garden bed, ensure the soil is loose and well-draining. Begonias like moisture, but they don't like to have "wet feet" where water sits for too long.
Regional Timing and Hardiness Zones
The United States is a large country with many different climates. Understanding your USDA hardiness zone can help you pinpoint the best week to start your begonias.
Zones 3 through 6 (Northern and Central US)
In these cooler climates, the growing season is relatively short. It is highly recommended to start your begonia tubers indoors in March. This ensures you get a full three or four months of blooming before the frost returns in the fall. You will likely move your plants outdoors in late May or early June.
Zones 7 through 8 (Southern and Coastal US)
In these regions, spring arrives earlier. You can start your tubers indoors in February or plant them directly outside in April or early May. Because the summers can get very hot, ensure your begonias have plenty of shade to keep them cool during the peak of July.
Zones 9 through 11 (Tropical and Warm Regions)
In these warm zones, begonias can sometimes be grown as perennials, though they still benefit from a rest period. You can plant them much earlier in the year, often in February or March, as the risk of frost is very low.
Regional Schedule at a Glance
- Zone 10: Start indoors in late December; Move outdoors in February.
- Zone 9: Start indoors in early January; Move outdoors in early March.
- Zone 7-8: Start indoors in early February; Move outdoors in April.
- Zone 5-6: Start indoors in mid-March; Move outdoors in late May.
- Zone 3-4: Start indoors in late March; Move outdoors in early June.
How to Prepare Your Tubers for Planting
Once you have determined the right time to plant, a little preparation goes a long way. This ensures the tubers transition from their dormant state to active growth as smoothly as possible.
Identifying the Top and Bottom
One of the most common questions we hear is "which side is up?" Begonia tubers have a distinct shape that makes this easy once you know what to look for.
The top of the tuber is concave, meaning it curves inward like a small bowl. This is where the stems will grow. The bottom of the tuber is rounded or domed. When you plant, the "bowl" should face up toward the sky. If you look closely at the bowl-shaped side, you may see small, rough bumps. These are the eyes where growth will begin.
Waking Up Dormant Tubers
Sometimes tubers arrive and look very quiet. If you don't see any sprouts yet, you can give them a gentle nudge. Place the tubers on a tray in a warm room with bright, indirect light. Do not bury them in soil yet.
Check them every few days. Within a week or two, you should see small pink or white buds starting to form. Once these sprouts are visible, the tuber is "awake" and ready to be tucked into some soil. For a broader refresher, see our Tips for Growing Tuberous Begonias.
Depth and Spacing: The Quiet Winners
Getting the timing right is the first step, but how you place the tubers in the soil is the second. Begonias do not like to be buried too deeply.
Planting Depth
In a pot or in the ground, you only need to cover the top of the tuber with about a half-inch to one inch of soil. If you bury them too deep, the sprouts may struggle to reach the surface, and the tuber could stay too wet. Think of it as giving them a light blanket rather than a heavy quilt. For a closer look at planting depth, read How Deep Should I Plant Begonia Tubers?.
Spacing for Growth
Begonias like a little breathing room. This helps air circulate around the leaves, which keeps the plants healthy.
- In garden beds, space the tubers about 8 to 12 inches apart.
- In a 12-inch hanging basket, 2 or 3 tubers are usually plenty.
- In a single 6-inch pot, one tuber is the perfect fit.
Key Takeaway: Shallow planting is best. Ensure the indented side faces up and is covered by no more than an inch of soil.
Transitioning Outdoors (Hardening Off)
If you started your begonias indoors, you cannot move them directly into the garden the moment the weather turns warm. They need a little time to get used to the "real world" of wind, sun, and temperature changes. This process is called "hardening off."
A Gentle Introduction
Start by taking your pots outside for just an hour or two in a shady, protected spot. Gradually increase the time they spend outside over the course of a week.
- Day 1-2: Two hours in full shade, then back inside.
- Day 3-4: Four hours in dappled light, then back inside.
- Day 5-7: All day outside, brought in only if a cold night is predicted.
After a week of this gradual introduction, your begonias will be strong enough to stay outside permanently. This extra effort prevents "sunscald" on the leaves and ensures your plants don't go into shock from the move.
Watering and Feeding at the Right Time
Timing also plays a role in how you care for your begonias throughout the summer. These plants have specific needs when it comes to moisture and nutrients.
The "Deep then Dry" Rule
When you first plant your tubers, water them once to settle the soil. After that, be very careful not to overwater. Until the plant has leaves, it doesn't have a way to process a lot of water.
Once the plant is established and growing vigorously, you can water more regularly. The best approach is to water deeply until it runs out the bottom of the pot, and then wait until the top inch of soil feels dry before watering again. This encourages the roots to grow deep into the soil.
Fertilizing for Blooms
Begonias are hungry plants. To keep them blooming all summer, they appreciate a little extra food. Start fertilizing once the plant has several sets of healthy leaves. A balanced, water-soluble fertilizer applied every two to three weeks is usually perfect. This gives them the energy they need to produce those huge, beautiful flowers.
What to Do When the Season Ends
The "when" of begonia care doesn't end in the spring. There is also a right time to bring them in for the winter. Because begonias are tropical, they will not survive a hard freeze.
Watching the Foliage
As the days get shorter and the nights get cooler in the fall, your begonias will naturally start to slow down. The leaves may begin to turn yellow. This is a sign that the plant is moving its energy back down into the tuber for the winter.
Lifting the Tubers
Once the first light frost hits, or if the temperatures are consistently dipping into the 40s, it is time to dig up your tubers (if they are in the ground) or bring your pots into a garage or basement.
- Cut back the stems: Leave about an inch of stem above the tuber.
- Dry them out: Let the tubers sit in a dry, cool spot for a few days until the remaining soil is easy to brush off.
- Store for Winter: Place the clean tubers in a box with some peat moss or sawdust and keep them in a cool, dark place (about 40-50°F) until next spring.
If you want a broader overview of seasonal care, visit our Begonia Planting & Care hub.
Summary of Begonia Timing
Managing the timing for your begonias is a simple way to ensure a successful garden. By respecting the plant's need for warmth and a slow start, you set the stage for a spectacular summer display.
- Indoor Start: 8-12 weeks before the last frost.
- Outdoor Move: When nighttime temperatures are consistently above 50°F.
- Soil Temp: Wait for 60°F for direct outdoor planting.
- Hardening Off: Take one week to transition plants from indoors to out.
- Winter Storage: Lift tubers after the first light frost or when leaves turn yellow.
We believe that anyone can grow beautiful begonias by following these basic steps. It is a rewarding experience to see a dormant tuber turn into a lush, flowering masterpiece. At Longfield Gardens, our goal is to help you enjoy every moment of the process, from the first sprout to the last autumn bloom.
Growing begonias is an exercise in patience that pays off in abundance. By matching your planting schedule to the rhythm of the seasons, you create a stress-free environment where your plants can truly shine.
For your next steps, we recommend checking your local frost dates and looking at the different varieties of begonias available. Whether you prefer the giant blooms of a Double variety or the graceful drape of a Hanging Basket type, there is a begonia perfectly timed for your garden.
FAQ
Can I plant begonia tubers in the winter?
You can start begonia tubers indoors during late winter, usually starting in February or March, depending on your climate. However, they should not be planted outdoors until all danger of frost has passed and the soil has warmed. Starting them indoors gives them the head start they need to bloom earlier in the summer. If you need help choosing the right starting window, the Begonia Planting & Care hub is a good place to begin.
What happens if I plant my begonias too early?
If begonias are planted outdoors while the weather is still cold or the soil is wet and chilly, the tubers may rot or simply fail to grow. They are tropical plants that require warmth to activate their growth. It is always better to wait for a consistent stretch of warm nights before moving them outside. You can also review our Shipping Information to better match delivery timing to your planting schedule.
How long does it take for begonia tubers to sprout?
Begonia tubers are notoriously slow to wake up and typically take 3 to 6 weeks to show their first sprouts. The exact timing depends on the warmth and light they receive. If your tubers are taking a while, don't worry—just keep them in a warm spot and be patient as they prepare to grow. For more background, see All About Begonias.
Do I need to soak begonia tubers before planting?
Soaking is not strictly necessary for begonia tubers, but some gardeners find that a brief 30-minute soak in room-temperature water helps "wake them up." Most importantly, ensure you plant them in moist (but not soggy) soil and keep them in a warm environment to encourage the first sprouts to appear. For more planting details, our How to Grow Begonias From Tubers guide has additional tips.
