Introduction
There is a special 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 elegance that thrives in those quieter, cooler corners of your yard. Whether you are looking for the massive, rose-like blooms of tuberous begonias or the steady, reliable color of wax begonias, these plants are a joy to grow. At Longfield Gardens, we want to help you make the most of your growing season by getting the timing just right.
Knowing when to tuck these beautiful plants into the earth is the first step toward a summer filled with vibrant color. Begonias are famous for their long blooming season, often staying bright and beautiful from early summer right through the first frost of autumn. Because they are tropical in nature, they have specific preferences for warmth and timing. This guide will help you identify the perfect window for planting so your begonias can grow strong and healthy.
We will cover everything from monitoring soil temperatures to starting your tubers early indoors. By following a few simple timing rules, you can ensure your begonias transition smoothly to the outdoors. Successful gardening is often about working with nature’s schedule, and begonias are a wonderful reward for your patience.
Understanding the Right Conditions for Begonias
Begonias are native to tropical and subtropical regions. This means they have no natural defense against freezing temperatures. To have the best experience, it is helpful to think of them as warm-weather guests. They are not like tulips or daffodils that enjoy the chilly spring soil. Instead, begonias prefer an environment that feels like a comfortable summer day.
The most important thing to remember is that begonias are very sensitive to frost. Even a light, overnight frost can damage the tender foliage or the crown of the plant. Because of this, the "best" time is never a specific date on the calendar. It is a set of conditions that occur in your specific backyard.
When we talk about planting time, we look at three main factors: the last frost date, the air temperature, and the soil temperature. When all three of these align, your begonias will settle in quickly and start growing without the stress of cold shocks.
The Magic Number: Soil and Air Temperatures
Many gardeners are eager to get their plants in the ground as soon as the sun starts shining in April. However, the air temperature can be deceiving. While it might feel warm to you while you are working in the garden, the soil often holds onto the winter chill much longer.
For begonias, the magic number for soil temperature is 60°F. If you plant a begonia tuber in soil that is colder than 55°F, it may sit dormant or, worse, begin to struggle in the damp, cold earth. Warm soil acts like an invitation for the roots to stretch out and start absorbing nutrients.
Air temperature is just as critical. You want to wait until nighttime temperatures are consistently above 50°F. Ideally, they should stay closer to 60°F. If you still have nights where the temperature dips into the 40s, it is best to keep your begonias in a protected area.
Key Takeaway: The perfect time to plant begonias outside is when the danger of frost has completely passed and the soil has warmed to at least 60°F.
Timing by Begonia Type
Not all begonias are exactly the same, and the type you choose might slightly change your timing strategy. While they all love warmth, the way they are grown from the start makes a difference.
Tuberous Begonias
These are often grown from fleshy, brown tubers that look a bit like small, hollowed-out bowls. Tuberous begonias, like the stunning varieties we carry, produce some of the largest and most intricate flowers. Because the tuber holds a lot of moisture, it is especially sensitive to cold, wet soil. These should always wait for the most stable, warm weather before going into the ground.
Wax Begonias (Fibrous-Rooted)
These are the common bedding plants you often see in garden centers. They have smaller, waxy leaves and clusters of red, white, or pink flowers. While they are still frost-tender, they are sometimes a tiny bit more resilient than the large-flowered tuberous types. However, they still will not survive a freeze.
Rex and Rhizomatous Begonias
These are often grown for their spectacular foliage. Many people keep these as houseplants during the winter. If you plan to move your indoor begonias outside for a summer "vacation," you must be even more careful. Since they have been living in a climate-controlled home, the transition to outdoor temperatures needs to be very gradual.
Starting Begonia Tubers Indoors for Early Color
One of the best ways to get a head start on the season is to start your tubers indoors. This is a great project for late winter or early spring. By starting them inside, you can essentially "cheat" the calendar and have plants that are already several inches tall by the time the outdoor weather is ready.
We recommend starting your tubers about 8 to 12 weeks before the average last frost date in your area. This gives the tubers plenty of time to wake up and develop a strong root system.
- Find the "Up" Side: Look for the indented or hollow side of the tuber. This is where the sprouts will emerge.
- Use a Shallow Tray: Fill a tray with moist potting soil. You don't need deep pots yet.
- Nestle the Tubers: Place the tubers on top of the soil, indented side up. Do not bury them deeply; just press them in so they are mostly covered but the top is visible.
- Provide Warmth and Light: A warm spot (around 70°F) and indirect light will encourage them to sprout.
- Water Carefully: Keep the soil moist like a wrung-out sponge, but never soaking wet.
Starting early indoors means that instead of waiting for a sprout to appear in June, you could have flowers starting as early as July. It is a rewarding way to extend the beauty of your garden.
Transitioning Your Begonias to the Garden
Once your begonias are growing well indoors and the weather outside is warming up, it is time for "hardening off." This is simply the process of getting your plants used to the outdoor environment. Even if it is warm, the wind and direct sunlight are much more intense than the conditions inside your home.
Start by taking your begonias outside for just an hour or two. Put them in a fully shaded, protected spot. Gradually increase the time they spend outside over the course of 7 to 10 days. By the end of the week, they should be ready to stay out all night, provided the forecast shows no cold snaps.
This transition is the bridge between "indoor time" and "outdoor time." Taking this extra step ensures that your plants don't experience transplant shock, which can stall their growth.
Regional Timing and USDA Zones
Because the United States is so large, the "best time" varies significantly depending on where you live. Your USDA hardiness zone is a helpful tool for understanding your local climate.
In southern regions (Zones 9-11), you may be able to plant begonias outside as early as March. In these areas, the soil warms up quickly. In fact, gardeners in the Deep South often have to worry more about the extreme heat of midsummer than the cold of spring. In these hot climates, begonias appreciate even more shade to stay cool.
In northern regions (Zones 3-6), you might need to wait until late May or even early June. It is common for these areas to have a "false spring" where it feels warm for a few days followed by a sudden frost. It is always better to wait an extra week than to rush and lose your plants to a surprise freeze.
We time our shipping at Longfield Gardens based on your hardiness zone. We want your tubers to arrive when it is nearly time to plant, or just in time to start them indoors if you live in a colder climate. See the shipping information for more details.
Preparing Your Planting Site
While you wait for the temperature to be just right, you can prepare the perfect home for your begonias. Getting the soil ready is a simple way to ensure success.
Begonias need soil that drains well. "Drainage" is a gardening term that describes how fast water leaves the soil. If water sits in a puddle for hours after a rain, the soil is too heavy for begonias. They have fleshy stems and tubers that can rot if they sit in soggy earth for too long.
If you have heavy clay soil, you can improve it by adding organic matter. Mixing in some compost or finely ground bark helps create air pockets in the soil. This allows water to move through and gives the roots room to breathe.
Begonias also prefer a spot with filtered light. While some "sun-tolerant" varieties exist, most begonias are happiest with morning sun and afternoon shade. The hot, direct afternoon sun can sometimes scorch their leaves, so a spot under a tree or on a north-facing porch is often ideal.
Simple Steps for Planting Begonias Outside
When the soil is 60°F and the nights are warm, it is finally time to plant. Whether you are moving started plants or dry tubers directly into the garden, the process is straightforward.
Planting Tubers Directly
If you live in a warm climate and are planting dry tubers directly into the ground, space them about 8 to 12 inches apart. Dig a shallow hole and place the tuber with the indented side facing up. Cover it with only about an inch of soil. If you bury them too deeply, they may struggle to push their sprouts to the surface. For additional guidance, see this guide to begonia tuber planting depth.
Planting Started Begonias
If you have plants that you started indoors or bought at a nursery, dig a hole that is twice as wide as the root ball. Place the plant in the hole so the top of the root ball is level with the surrounding soil. If you plant them too deep, the stems might rot. If you plant them too shallow, the roots might dry out.
Watering After Planting
After you tuck them in, give them a good drink of water. This helps settle the soil around the roots and removes any large air pockets. From that point on, follow the "deep, then dry" rule. Water the soil deeply, then wait until the top inch of soil feels dry before watering again.
What to do next:
- Check your local average last frost date.
- Monitor your nighttime temperatures for a week.
- Prepare your containers or garden beds with well-draining soil.
- Start hardening off any indoor plants once the weather stabilizes.
Conclusion
The best time to plant begonias outside is a window of opportunity created by warmth and safety from frost. By waiting for the soil to reach 60°F and ensuring the nights stay mild, you give these tropical beauties the best possible start. Whether you choose to start them early indoors for a head start or wait for the natural warmth of late spring, the result will be a season of spectacular color.
At Longfield Gardens, we believe that gardening should be a rewarding and enjoyable experience for everyone. Begonias are one of the most reliable ways to bring life to the shady parts of your yard. With just a little bit of patience in the spring, you will be rewarded with a lush, flowering sanctuary that lasts all summer long.
We are here to support you with high-quality begonia tubers and the practical advice you need to see them flourish. Now is the perfect time to look at your garden, find those quiet shady spots, and imagine the vibrant colors that will soon be growing there.
"Timing is the quiet secret to gardening success. When you wait for the warmth, you aren't just planting a flower; you are giving it the perfect environment to thrive."
FAQ
Can I plant begonias if there is still a chance of frost?
It is best to wait until the danger of frost has completely passed. Begonias are tropical plants with high water content in their stems and leaves, making them very susceptible to freezing. If a surprise frost is predicted after you have planted, you should cover your begonias with a frost blanket or a bucket overnight to protect them.
Do begonias need to be in the shade all day?
Most begonias prefer "dappled shade" or a mix of morning sun and afternoon shade. While they don't want to be in a dark corner with no light, the intense heat of the afternoon sun can burn their leaves. A spot that gets 2-4 hours of morning light followed by shade for the rest of the day is usually perfect for most varieties.
Is it better to start begonia tubers indoors or plant them directly outside?
Both methods work, but starting them indoors 8-12 weeks before the last frost gives you a much longer blooming season. Begonias can be slow to wake up and start growing. By starting them inside, you ensure they are already robust plants by the time the outdoor weather is warm enough for them. Follow this step-by-step indoor-starting guide for additional help.
Why are my begonia leaves turning yellow after I planted them?
Yellow leaves can sometimes be a sign of overwatering or poor drainage. Begonias like moist soil, but they do not like to sit in water. Ensure your soil is well-draining and that you are allowing the top inch of soil to dry out between waterings. If you recently moved them outside, it could also be a sign of minor transplant shock, which they should outgrow in a week or two.
