Table of Contents
- Introduction
- Determining the Best Time to Plant
- Starting Begonia Tubers Indoors
- Transitioning to the Garden: Outdoor Planting
- Regional Timing and Hardiness Zones
- How to Plant for Best Results
- Managing the Sprouting Period
- Moving Plants Outside: The Hardening Off Process
- The Bloom Timeline: What to Expect
- End of Season Timing: When to Dig and Store
- Conclusion
- FAQ
Introduction
There is a unique sense of excitement that comes with the arrival of spring. As the days grow longer and the sun begins to feel warmer, gardeners everywhere start thinking about the lush, colorful displays they want to create. Tuberous begonias are a favorite for these moments because they offer some of the most spectacular, rose-like blooms and vibrant foliage for those tricky, shaded areas of the yard. At Longfield Gardens, we believe that gardening is most rewarding when it feels simple and successful.
Knowing exactly when to plant begonia tubers is the first step toward enjoying a season full of flowers. Because begonias are tropical in nature, they have specific needs when it comes to temperature and timing. This guide will help you understand the best window for planting, whether you are starting them indoors or directly in the garden. We will cover how to time your planting based on your local weather and how to ensure your begonias have the best possible start.
By following a few basic rules of timing, you can enjoy these beautiful flowers from mid-summer all the way until the first frost of autumn.
Determining the Best Time to Plant
The most important thing to know about begonias is that they are very sensitive to cold. Unlike spring-flowering bulbs like tulips or daffodils, which go into the ground in the fall, begonia tubers must wait until the warmth of spring arrives. The "when" of planting depends entirely on whether you are starting them indoors or waiting to plant them directly outside.
If you want the earliest possible blooms, you should start your tubers indoors. For most people in the United States, this happens in late winter or early spring. If you prefer to plant them directly into your garden beds or outdoor containers, you must wait until the threat of frost has completely passed and the soil has warmed up.
Regardless of where you live, the goal is to provide the tubers with a long, warm growing season. Begonias take some time to wake up from their winter rest, often requiring several weeks to show their first sprouts. By getting the timing right, you ensure the plant has enough energy to produce its big, showy flowers before the season ends.
Starting Begonia Tubers Indoors
Starting your tubers indoors is one of the best ways to set yourself up for success. Because begonias have a relatively slow start, giving them a head start inside your home allows them to grow roots and stems while the weather outside is still too cold.
Why Start Early?
When you start begonias indoors, you essentially extend your summer. A tuber started in March or April will often begin blooming in June or July. If you wait until May or June to plant them outdoors, you might not see flowers until late August. Starting early gives the plant more time to develop the strong foliage needed to support those heavy, beautiful blooms.
The Indoor Planting Timeline
The ideal time to start begonia tubers indoors is roughly 8 to 12 weeks before the average last frost date in your area. For many gardeners, this falls between late February and early April. We ship our orders from our facility in Lakewood, New Jersey, based on these dates to ensure your tubers arrive at the right time for your specific climate.
If you aren't sure when your last frost date is, you can check with your local agricultural extension office or use a reliable online frost date calculator. Once you have that date, simply count back about two or three months. This window gives the tuber enough time to sprout, grow a few sets of leaves, and become a sturdy little plant before it ever touches outdoor soil.
Creating the Right Environment
While timing is the biggest factor, the environment where you start your tubers also matters. Begonias need warmth to wake up. They prefer a consistent temperature between 60°F and 70°F. A warm mudroom, a laundry room, or even the top of a refrigerator can provide the gentle heat they need to start growing. You do not need bright light until you see green growth breaking the surface of the soil.
Transitioning to the Garden: Outdoor Planting
If you choose not to start your begonias indoors, or once your indoor-started plants are ready to move, you must be patient. Moving too quickly is the most common mistake made with these tropical beauties.
Watching the Weather
Begonias are not fans of the "cold shoulder." Even a light frost can damage or kill the tender new growth. You should only plant begonia tubers or move started plants outdoors once the danger of frost has passed 100%. In many northern states, this might not be until late May or early June.
It is also helpful to watch the nighttime temperatures. Begonias thrive when the nights stay consistently above 50°F. If the nights are still dipping into the 40s, the plants may sit dormant and refuse to grow, even if it is sunny during the day.
Soil Temperature Matters
Timing your planting isn't just about the air; it’s about the soil. Soil temperature is how fast or slow the ground warms up after winter. Begonias prefer soil that feels warm to the touch, ideally around 60°F.
If you are planting directly into garden beds, wait until you see other spring plants fully leafed out. If you are planting in containers or hanging baskets, the soil will warm up faster than the ground, which can give you a slight advantage in timing. However, you must still be ready to bring those pots inside if a surprise late-season cold snap is forecasted.
Regional Timing and Hardiness Zones
Your location in the United States plays a huge role in when you should start your gardening journey. The USDA Hardiness Zones are a helpful way to understand your climate.
In warmer regions, like Zones 9 through 11, begonias can often be planted much earlier, or even left in the ground in some cases. However, for most of the country (Zones 3 through 8), begonias are treated as annuals or "tender perennials" that must be started fresh or brought in for the winter.
Shipping Schedules and Your Local Frost Date
We time our shipping at Longfield Gardens to coincide with the best planting window for your specific zone. We typically begin shipping to the warmest areas first and move north as the weather improves. This helps ensure that your package isn't sitting in a cold mailbox or a freezing delivery truck for too long. When your package arrives, it is a great signal that it is time to start your indoor planting or prepare your outdoor pots.
How to Plant for Best Results
Once you have identified the right time to plant, the actual process is quite simple. Getting the orientation and depth right will help the plant sprout more quickly and grow a strong root system.
Identifying the Top of the Tuber
Begonia tubers have a unique look. They are usually brown, somewhat fuzzy, and shaped like a thick disc or a shallow bowl. One side is rounded (convex), and the other side has a dip or a hollow spot (concave).
The hollow, indented side is the top. This is where the stems and leaves will eventually emerge. Sometimes, if you look closely, you may even see small pink or white buds starting to form in that hollow area. The rounded side is the bottom, where the roots will grow.
Depth and Spacing Rules
Begonias do not like to be buried deep. In fact, planting them too deep can cause the tuber to rot before it ever has a chance to grow.
- For Indoor Starting: Place the tuber hollow-side up on top of moist potting soil. You can lightly press it in so it is about half-covered, or cover it with just a very thin layer of soil (about 1/2 inch).
- For Outdoor Planting: Dig a shallow hole and place the tuber hollow-side up. Cover it with about 1 inch of soil.
- Spacing: If you are planting in the ground, space the tubers about 8 to 12 inches apart. In containers, you can place them slightly closer, about 6 inches apart, to create a fuller look.
For a closer look at placement, see How Far Apart Should Begonias Be Planted?
Managing the Sprouting Period
After you have planted your tubers at the correct time, there is a period of waiting. This is often the time when gardeners worry the most, but patience is key. Begonias are not "fast" starters.
It can take anywhere from 3 to 6 weeks to see the first green shoots. During this time, the tuber is busy growing a root system beneath the soil. It is important to keep the soil lightly moist but never soggy. "Drainage" is the word for how quickly water leaves the soil; you want a mix that allows water to flow through easily so the tuber doesn't sit in a puddle.
If you are starting them indoors, once you see those first green leaves, move the pots to a bright window with indirect light. They don't need the harsh, direct sun of midday, which can actually scorch their tender leaves.
Moving Plants Outside: The Hardening Off Process
If you started your begonias indoors, you cannot move them directly into the garden the moment the sun comes out. They need a transition period called hardening off. This is a way of getting the plants used to the wind, varying temperatures, and brighter light of the outdoors.
- Start Slow: On a warm, calm day, set your pots outside in a shady, protected spot for an hour or two.
- Increase Time: Gradually increase the amount of time they spend outside each day over the course of a week.
- Monitor Light: Move them into slightly brighter (but still dappled) light as the week progresses.
- Check the Nights: Bring them back inside every night until the week is over and nighttime temperatures are safely above 50°F.
This extra week of effort ensures that your plants don't go into "shock," which can stall their growth and delay your flowers.
The Bloom Timeline: What to Expect
Once your begonias are established in their summer homes, they are relatively low-maintenance. The timing of their blooms is one of their best features. Most tuberous begonias will begin to flower in mid-summer and continue right through until the weather turns cold in the fall.
Depending on the variety you chose, you may see different types of blooms. At Longfield Gardens, we offer several beautiful options:
- Roseform and Picotee: These produce large, double blooms that look remarkably like roses.
- Hanging Basket (Pendula): These have a cascading habit, making them perfect for elevated pots where the flowers can drape over the sides.
- Scented Varieties: These provide a delicate fragrance that is rare in the begonia world.
- Fimbriata: These have fringed petals that add a unique texture to the garden.
By planting at the right time, you ensure these varieties have the maximum number of days to show off their colors. As long as you keep them watered and occasionally give them a little liquid fertilizer, they will reward you with a non-stop flower show.
End of Season Timing: When to Dig and Store
Just as the beginning of the season is defined by frost, so is the end. When the first light frost of autumn arrives, the foliage of your begonias will likely turn black or wilt. This is the signal that the growing season is over and it is time to prepare the tubers for their winter nap.
In most zones, you will need to dig up the tubers to save them for next year. Wait until the leaves have yellowed or the first frost has hit. Cut the stems back to about an inch above the tuber and carefully lift them from the soil.
Let the tubers dry in a cool, protected spot for a few days until any remaining soil can be gently brushed off. Store them in a box with some peat moss or sawdust in a cool, dark place (like a basement) where they won't freeze. This simple cycle allows you to enjoy the same beautiful plants year after year.
What to Do Next
- Find your local average last frost date.
- Decide if you want to start indoors (8-12 weeks early) or outdoors (after frost).
- Order your favorite varieties from us to ensure they arrive at the right time.
- Prepare your pots with a well-draining potting mix.
Conclusion
Planting begonia tubers is a rewarding way to bring elegance and color to the shaded corners of your garden. Success truly comes down to respecting the plant's tropical roots and following the rhythm of the seasons. By starting your tubers indoors during the late winter or waiting for the reliable warmth of late spring to plant outside, you provide the foundation for a spectacular summer display. We love how begonias make gardening feel accessible, offering high-impact beauty with just a little bit of planning.
Remember to keep your tubers warm while they sprout and protect them from the chill of early spring. With a bit of patience and the right timing, your garden will be the envy of the neighborhood.
"Tuberous begonias are the gems of the shade garden. Getting the timing right is the simplest way to ensure they shine all summer long."
We invite you to explore our selection of premium begonia tubers and start planning your most beautiful garden yet.
FAQ
Can I plant begonia tubers directly in the ground in March?
In most parts of the United States, March is far too early to plant begonia tubers directly in the ground. Because they are tropical plants, they will rot in cold, damp soil or be killed by late-season frosts. Unless you live in a very warm, frost-free climate, it is much better to start them indoors in March and wait until May or June to move them outside.
How do I know which side of the begonia tuber is the top?
The top of a begonia tuber is the side with a hollow or "bowl-shaped" indentation. You may also see small, pinkish buds or the remnants of last year's stems in this dip. The rounded, smooth side is the bottom where the roots will grow. Always plant them with the hollow side facing up toward the sky.
What happens if I plant my begonias outside too early?
If begonias are planted outside before the soil has warmed up and the risk of frost is gone, several things can happen. The most common result is that the tuber will rot in the cold, wet soil. If the plant has already sprouted, a single night of frost can turn the leaves black and kill the plant. It is always better to wait an extra week for warm weather than to risk planting too early.
Do begonia tubers need light to sprout indoors?
Begonia tubers do not actually need light to begin the sprouting process, but they do need warmth. You can keep your pots in a warm room away from a window until you see the first green shoots breaking through the soil. Once those leaves appear, you should move them to a spot with bright, indirect light so the stems grow strong and sturdy rather than tall and "leggy."
Safety Note: Please keep in mind that many garden plants, including begonias, can be toxic to cats and dogs if eaten. Always check with a reliable source regarding plant toxicity and keep tubers and plants out of reach of curious pets and children. Results in the garden will always vary based on your local weather, soil quality, and specific microclimate.