Introduction
There is a unique kind of excitement that comes with planning a shade garden. While many flowers crave the intense heat of the midday sun, begonias offer a lush, tropical escape in those cooler, quieter corners of the yard. Whether you are looking forward to the elegant, rose-like blooms of upright tuberous begonias or the cascading colors of trailing varieties, these plants are a highlight of the summer season. At Longfield Gardens, we enjoy helping gardeners transform their outdoor spaces with these versatile and reliable performers.
Knowing the right moment to get your begonias into the ground—or into their first indoor pots—is the most important step toward a successful season. Because these plants are native to tropical regions, they have very specific preferences regarding temperature and timing. This guide is designed for home gardeners who want to understand the seasonal rhythms of begonias, from starting tubers indoors to the final transition into the garden. If you love a classic upright look, start with our Upright Double Begonias collection.
We will cover the ideal temperature ranges for planting, how to calculate your start dates based on local frost schedules, and how to ensure your plants are strong enough for the outdoors. By the end of this article, you will have a clear timeline for your garden. The secret to vibrant, season-long begonia blooms is simply matching your planting schedule to the natural warmth of the spring season. For a broader overview of begonia types and care, see our All About Begonias guide.
Understanding the Begonia Life Cycle
To understand the best time to plant begonias, it helps to look at where they come from. Most garden begonias originated in tropical and subtropical climates where the air is humid and the temperatures stay warm year-round. They do not have a natural "winter mode" that includes freezing temperatures. In the United States, we treat most begonias as annuals or as tender perennials that need to be brought indoors when the weather turns cold.
Tuberous begonias grow from a thick, fleshy root called a tuber. This tuber acts as a storage unit, holding the energy the plant needs to push out its first leaves and flowers. When the tuber is dormant, it is resting. To wake it up, it needs a combination of moisture and consistent warmth. If you plant too early in cold, wet soil, the tuber may stay dormant or suffer from rot. If you plant at the right time, the tuber responds quickly, sending up sturdy stems and lush foliage.
The Best Time to Plant Begonias Outdoors
For most gardeners, the "best" time to plant is determined by two main factors: the date of the last frost and the temperature of the soil. Begonias are extremely sensitive to cold. Even a light frost can damage the succulent stems and leaves, and a hard freeze will often kill the plant entirely.
Waiting for the Last Frost
The safest rule of thumb is to wait until all danger of frost has passed in your specific area. Depending on where you live, this could be as early as March in the South or as late as June in the far North. However, the last frost date is only the beginning of the window. Begonias prefer "settled" spring weather. This means the nights are no longer dipping into the 30s or 40s (Fahrenheit), and the days feel consistently mild.
Monitoring Soil and Air Temperatures
Begonias are at their happiest when the air temperature is consistently above 60°F during the day and does not drop below 50°F at night. Soil temperature is equally important. Drainage—which is how fast water leaves the soil—is better in warm soil, and the roots of the begonia will grow much faster when the ground is at least 60°F. If the soil is still cold and clammy, the plant will sit idle, making it more vulnerable to pests and disease.
Simple Steps for Outdoor Timing
- Check your local "average last frost date" through a regional weather service or extension office.
- Wait at least one to two weeks after that date to ensure a late cold snap doesn't catch you by surprise.
- Use a soil thermometer to check that the ground has warmed up to 60°F.
- Observe the trees and shrubs in your neighborhood; when they are fully leafed out, the environment is usually warm enough for begonias.
Key Takeaway: The best time to plant begonias outdoors is in late spring when the soil is warm and the threat of frost is completely gone.
Why You Should Start Tuberous Begonias Indoors
While you can wait and plant your begonia tubers directly in the garden once the weather is warm, many gardeners prefer to "wake them up" indoors first. This is a common practice because tuberous begonias have a relatively long growing cycle. They take their time to get established, and starting them early gives you a head start on the blooming season.
The 8 to 12 Week Window
We recommend starting your begonia tubers indoors about 8 to 12 weeks before your average last frost date. This early start allows the plant to develop a strong root system and several inches of top growth before it ever touches outdoor soil. When you finally move them outside in late spring, they will be ready to start blooming much sooner than if they had started from scratch in the garden.
Creating a Tropical Microclimate Indoors
When you start begonias early, you are essentially mimicking their native habitat inside your home. They need a warm spot with indirect light. A kitchen counter, a dedicated plant shelf, or a sunroom is ideal. You don’t need a greenhouse to be successful; a consistent room temperature of 65°F to 75°F is perfect for encouraging those first sprouts.
Benefits of Starting Early
- Earlier Blooms: You can enjoy flowers in early summer rather than late summer.
- Stronger Plants: Plants started indoors have time to grow sturdy stems that can better handle wind and rain.
- Better Control: It is much easier to manage moisture levels in a small pot on your counter than in a large garden bed during a rainy spring.
Timing for Different Begonia Varieties
Not all begonias are exactly the same, and the timing can shift slightly depending on the variety you choose. At Longfield Gardens, we offer several types of tuberous begonias, and each has its own charm.
Upright Tuberous Begonias
These include varieties like the Double, Begonia Upright Double Roseform Pink, and Fimbriata begonias. They grow on sturdy, upright stems and are perfect for garden borders and window boxes. These are the most common varieties to start indoors 8 to 12 weeks early. They produce large, showy flowers that look best when the plant has had plenty of time to build up its foliage.
Trailing (Pendula) Begonias
Trailing begonias are specifically bred for hanging baskets and the edges of containers. Their stems are more flexible, allowing them to drape beautifully over the sides of a pot. Because these are almost always grown in containers, you can sometimes start them a little later than upright varieties, but they still benefit from that 8-week indoor head start. A good example is Begonia Hanging Golden Balcony.
Specialty Varieties
Varieties like the Picotee (which has a contrasting color on the petal edges) or the Marmorata (with marbled patterns) follow the same timing as other tuberous types. The main difference is the visual impact they provide once the blooming season begins. Regardless of the flower shape, the "when" remains the same: start indoors in late winter/early spring and move outdoors in late spring/early summer. A good example is Begonia Upright Double Picotee White.
How to Start Begonias Indoors Step-by-Step
Timing your planting is only half the battle; knowing how to set them up for success during those first few weeks is the other half. Starting tubers is a simple process that requires just a few supplies.
Preparing the Containers
You do not need large pots to start. Shallow trays or small individual pots with drainage holes work best. Fill them with a high-quality, peat-based potting mix. This type of soil is light and holds moisture without becoming heavy or packed down. For more container-growing help, see our Can Begonias Be Planted in Pots? Container Garden Guide.
Placing the Tubers
Look at your begonia tuber. One side will be slightly indented or "hollowed out." This is the top. The rounded, smooth side is the bottom.
- Place the tuber on top of the moist soil with the hollow side facing up.
- Press it gently into the soil so it is mostly nestled in, but do not bury it deeply. A light dusting of soil over the top (about half an inch) is plenty.
- Space tubers about 2 to 3 inches apart if using a tray.
For a more detailed depth guide, see How Deep to Plant Tuberous Begonias in Hanging Baskets.
Watering and Light
Water the soil lightly after planting to settle the tuber. You want the soil to feel like a wrung-out sponge—damp but not dripping. Place the tray in a warm spot with bright, indirect light. Avoid direct, hot sunlight, which can dry out the tubers before they have a chance to sprout. You should see the first pink or green "eyes" (buds) appearing within 2 to 4 weeks.
Transitioning to the Garden: The Hardening Off Process
One of the most common mistakes gardeners make is moving plants directly from a cozy indoor environment to the outdoors all at once. This can cause "transplant shock," where the leaves turn yellow or drop because the change in temperature and light was too sudden. The timing of this transition is just as important as the initial planting date.
What is Hardening Off?
Hardening off is the process of gradually acclimating your plants to outdoor conditions. This usually takes about 7 to 10 days. You are teaching the plant how to handle real wind, direct sun, and fluctuating temperatures.
A Sample Hardening Off Schedule
- Days 1-2: Place your begonias outside in a fully shaded, protected spot for 2 to 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. Move them into a spot with dappled sunlight for an hour or two.
- Days 5-6: Leave them out all day. By now, they should be able to handle a bit more light and wind. If the nights are staying above 50°F, you can leave them out overnight in a protected area.
- Days 7-10: Your plants are now ready to be permanently planted in their outdoor containers or garden beds.
Timing the Move
Always check the 10-day weather forecast before you begin this process. If you see a cold front or a period of heavy rain coming, wait a few days. It is much better to keep the plants indoors for an extra week than to rush them into harsh weather.
What to do next:
- Check your frost date and count back 10 weeks to find your indoor starting date.
- Order your tubers from us early; our Shipping Information page explains timing by zone.
- Purchase a fresh bag of potting mix and clean your starter trays.
- Identify a warm, bright spot in your home for the "waking up" phase.
Selecting the Right Location for Your Begonias
Once the timing is right and the plants are hardened off, you need to choose their permanent home. The best time to plant begonias won’t matter if the location doesn't meet their needs.
Light Requirements
Most begonias thrive in partial shade. This means they like about 4 to 6 hours of sunlight, preferably in the morning. The afternoon sun in many parts of the U.S. is too intense and can scorch the delicate leaves. If you have a spot under a leafy tree, on a north-facing porch, or along a shaded walkway, your begonias will be very happy. For more help matching begonias to the right light, see Where to Plant Begonias: Sun or Shade?.
Soil and Drainage
As we mentioned earlier, drainage is how fast water leaves the soil. Begonias have succulent stems, which means they store a lot of water. Because of this, they are prone to rotting if they sit in soggy soil.
- In Containers: Use a potting mix that contains perlite or vermiculite to help with airflow.
- In the Ground: If your soil is heavy clay, we suggest planting in raised beds or amending the soil with compost to loosen it up.
Planting Depth and Spacing
When the best time to plant finally arrives, getting the depth and spacing right ensures your plants have room to breathe and grow.
In the Garden
If you are planting directly into a garden bed, space your begonias 8 to 12 inches apart. This might seem like a lot of space when they are small, but they will quickly fill in. Good airflow between plants is the best way to prevent powdery mildew, a common fungus that looks like white dust on the leaves. For a deeper dive into spacing, see How Far Apart to Plant Bedding Begonias: Spacing Guide. Plant the tubers or the root ball of your started plants so the top is just level with or slightly below the soil surface.
In Containers
Begonias are excellent container plants. In a 12-inch pot, you can plant three tubers for a very full look. In a hanging basket, two or three trailing tubers will create a beautiful curtain of color. Ensure the container has plenty of drainage holes at the bottom so excess water can escape easily.
Caring for Begonias Throughout the Season
Once your begonias are planted at the ideal time and in the ideal place, they require very little "work" to keep them looking beautiful. Consistency is the secret to long-lasting blooms.
Watering Correctly
Instead of watering a little bit every day, we recommend watering deeply and then letting the top inch of soil dry out. This encourages the roots to grow deeper into the soil. Avoid getting water on the leaves if possible; watering at the base of the plant keeps the foliage dry and healthy.
Fertilizer for More Flowers
Begonias are "heavy feeders," meaning they use a lot of nutrients to produce those big, showy flowers. Once your plants have several sets of leaves and are settled in their outdoor home, you can start using a balanced, water-soluble fertilizer every two to three weeks. Follow the instructions on the label to give them just the right amount of boost.
Deadheading
"Deadheading" is simply the act of removing old, faded flowers. While many modern begonia varieties are "self-cleaning" (the flowers fall off on their own), removing the spent blooms helps the plant look tidy and encourages it to put more energy into creating new buds. Simply pinch off the faded flower at the stem.
Regional Timing and USDA Hardiness Zones
The United States is a large country with many different climates, which means the "best time" for a gardener in Florida is different from a gardener in Maine. Most begonias are hardy only in USDA zones 9 through 11. For a map of your zone, see our Hardiness Zone Map. In these warm areas, begonias can sometimes stay outdoors year-round.
For the rest of us (zones 2 through 8), the timing is strictly seasonal.
- The South and Southwest: You may be able to plant outdoors as early as March or April. Be mindful of the intense summer heat; your begonias may need more shade than those in cooler climates.
- The Midwest and Northeast: Late May or early June is the typical window for outdoor planting. Starting indoors is highly recommended here to make the most of the shorter growing season.
- The Pacific Northwest: The cool, damp springs in this region mean you should wait until the soil is truly warm, often in June, to avoid rot issues.
Common Timing Questions
Many gardeners worry they have missed their window or started too late. The good news is that begonias are quite forgiving.
Is it ever too late to plant?
If you find yourself in mid-June with a bag of tubers, go ahead and plant them! While you may have a shorter blooming season than someone who started in March, you will still get plenty of beautiful flowers throughout August and September. Since begonias continue to bloom until the first frost of autumn, a late start is better than no start at all.
What if I plant too early?
If you have already planted your begonias outdoors and a surprise frost is predicted, don’t panic. You can protect them by covering them with a frost blanket, an old bedsheet, or even an inverted plastic bucket for the night. Remove the cover as soon as the sun comes up and the temperatures rise above freezing.
Preparing for the End of the Season
Just as timing is important in the spring, it plays a role in the fall as well. Tuberous begonias will naturally start to slow down as the days get shorter and the nights get cooler.
Bringing Tubers In for Winter
When the first light frost hits, the foliage of your begonias will turn black and wilt. This is your signal that the season is over. This is actually a great time to save your tubers for next year.
- Dig up the tubers carefully.
- Cut off the wilted stems, leaving about an inch of growth.
- Let the tubers dry in a cool, dry place for a few days.
- Store them in a box of peat moss or sawdust in a cool (but not freezing) basement or closet.
By saving your tubers, you will have even larger, more spectacular plants to put out at the "best time" next spring!
Conclusion
Finding the best time to plant begonias is a matter of matching the plant's tropical needs with your local weather patterns. By starting your tubers indoors 8 to 12 weeks before the last frost and waiting for warm, 60°F soil before moving them outside, you set the stage for a spectacular display. These plants are a rewarding choice for any gardener, offering high-impact color for very little effort once the basics of timing are met.
At Longfield Gardens, we want you to feel confident and excited every time you pick up a trowel. Gardening is a journey of observing the seasons and enjoying the growth along the way. Our 100% Quality Guarantee is part of that promise. Whether you are planting a single pot for your porch or a whole border of cascading blooms, the result is always worth the wait.
- Start tubers indoors 8-12 weeks before the last frost for early color.
- Wait for consistent 60°F soil and air temperatures before outdoor planting.
- Use the hardening-off process to transition plants safely.
- Choose a partially shaded spot with excellent drainage for the best results.
"The secret to a beautiful begonia garden isn't a green thumb—it's a warm soil thermometer and a little bit of patience in the spring."
We invite you to explore Begonia Upright Double Superba Mix - Bulk Offer and start planning your most beautiful shade garden yet.
FAQ
Can I plant begonias in full sun?
Most tuberous begonias prefer partial shade, especially during the hottest part of the day. Some wax begonias with bronze foliage can handle more sun, but for the large-flowered tuberous varieties we carry, morning sun and afternoon shade are the ideal combination. If you must plant them in a sunnier spot, ensure they receive plenty of water to compensate for the heat.
How do I know which side of the begonia tuber is the top?
The top of a begonia tuber is slightly indented or bowl-shaped. This is where the new stems and leaves will sprout. The bottom is rounded and usually has a smoother texture. If you accidentally plant one sideways, the plant will usually figure it out and grow toward the light, but planting it hollow-side-up is the best way to get a fast start.
Why are my begonia tubers taking so long to sprout indoors?
Begonia tubers are not in a hurry! It can take anywhere from two to four weeks to see the first signs of life. The most common reason for a slow start is a room that is too cool. Move your starter tray to a warmer spot, such as the top of a refrigerator or near a heating vent (but not directly on it), to help speed up the process.
Do I need to soak begonia tubers before planting?
You do not need to soak begonia tubers before planting them. In fact, soaking them for too long can actually lead to rot. Simply plant them in moist potting mix, and the tuber will naturally absorb the hydration it needs to wake up. Consistency in soil moisture is much more effective than a pre-planting soak.
