Introduction
There is nothing quite like the excitement of seeing the first vibrant blooms of a begonia tucked into a shady corner of the garden. Whether you are looking for the trailing elegance of a hanging basket or the bold, rose-like flowers of an upright variety, these plants bring nonstop color from midsummer all the way until the first frost. At Longfield Gardens, we want to help you achieve that lush, tropical look in your own backyard by getting the timing just right.
This guide is designed for home gardeners who want to understand exactly when plant begonias for the best results. We will cover the ideal temperatures for planting, how to start your tubers indoors for an early jump on the season, and when it is safe to move them into your outdoor garden beds. By following a few simple timing rules, you can enjoy a long season of beautiful foliage and flowers.
Success with begonias depends more on patience than on complicated gardening tricks. Because these plants are tropical in origin, they thrive in warmth and can be quite sensitive to the cold. Learning to read your local weather and soil conditions is the most important step in your gardening journey.
The Golden Rule of Begonia Timing
The most important thing to remember about begonias is that they are tropical plants. They love humidity and warm temperatures, but they have absolutely no tolerance for frost. If you plant them too early, the cold soil can cause the tubers to sit dormant or even rot before they have a chance to grow.
The best time to plant begonias outdoors is when the soil has warmed to at least 60°F and the nighttime air temperatures are consistently above 50°F. For most gardeners in the United States, this window opens in late spring or early summer. If you still have your winter coat nearby, it is probably too early to put your begonias in the ground.
Waiting for the right conditions might feel difficult when you are eager to get your garden started, but your plants will thank you. A begonia planted in warm, welcoming soil will quickly outpace one that was stunted by an early spring cold snap. Patience in May leads to a spectacular display in July.
Why Soil Temperature Matters
Soil temperature is often more important than air temperature when it comes to the "when" of planting. Tubers are the energy storage centers of the plant. When they are placed in cold, damp soil, they stay in a state of sleep. If the soil is also wet from spring rains, that dormant tuber can easily succumb to rot.
By waiting until the soil reaches 60°F, you ensure the tuber "wakes up" immediately. Roots will begin to reach out, and the first sprouts will push through the soil surface within just a few weeks. You can check your soil temperature with a simple kitchen thermometer or a dedicated soil probe from a local garden center.
Air Temperature and Nighttime Lows
Begonias are very sensitive to "chilling injury." This can happen even if there isn't a hard freeze. If nighttime temperatures dip into the 40s, the foliage can turn yellow or drop off, and the plant's growth will stall.
Keep an eye on your local ten-day forecast. If you see a string of nights where the lows stay above 50°F or 55°F, you have reached the safe zone. This is usually about two to three weeks after the date of your last expected spring frost.
Key Takeaway: Begonias are tropical plants that require warm conditions. Never rush them into the ground until the soil is 60°F and the danger of frost is long gone.
When to Start Begonias Indoors
If you live in a northern climate with a short growing season, you might worry that your begonias won't have enough time to reach their full potential. The solution is to start your tubers indoors. This gives the plants a "head start" so they are already established and perhaps even blooming by the time you move them outside.
We recommend starting begonia tubers indoors about 8 to 12 weeks before your average last frost date. For many regions, this means planting them in pots inside your home during late February or March. This timing ensures that by late May or early June, you have a sturdy plant ready for the garden.
Starting indoors is an easy and rewarding process. You don't need a professional greenhouse; a bright windowsill or a simple grow light setup is plenty. The goal is to mimic the warm, humid environment the plant naturally loves.
Setting Up Your Indoor Planting Station
To start your tubers, you will need a shallow tray or individual small pots with drainage holes. Use a high-quality, well-draining potting mix. Begonias do not like to sit in soggy soil, so "drainage" (how fast water leaves the soil) is critical.
- Fill your containers with moist (but not soaking) potting mix.
- Place the tubers on top of the soil with the hollow, indented side facing up.
- Cover the tubers with about an inch of soil.
- Place the containers in a warm spot, ideally around 70°F.
Managing the Wait
Once planted, begonias take their time to sprout. It may take two to four weeks before you see any green growth appearing above the soil. This is perfectly normal. During this time, water very sparingly. The tuber has all the moisture it needs to get started. Overwatering at this early stage is the most common reason for a tuber failing to grow.
Once you see sprouts, move the pots to a bright location with indirect sunlight. If the light is too dim, the plants will become "leggy," meaning they grow tall and weak as they reach for the sun. A little bit of gentle air circulation from a fan can also help strengthen the stems as they grow.
What to Do Next:
- Identify your local last frost date using a regional calendar.
- Count back 10 weeks from that date to find your indoor start day.
- Gather your pots and a fresh bag of high-quality potting mix.
- Check your tubers to ensure they are firm and healthy before planting.
Hardening Off: The Transition Period
One of the most critical timing steps is the transition from the cozy indoors to the unpredictable outdoors. This process is called "hardening off." If you move a begonia directly from a 70°F living room to a breezy, 55°F patio, the shock can be too much for the plant to handle.
Plan for a transition period of about 7 to 10 days. This should happen once the outdoor temperatures meet the safety requirements we discussed earlier. Think of this as "toddler steps" for your plants to get used to the real world.
A Typical Hardening Off Schedule
- Days 1-2: Place your plants in a shaded, protected spot outside for just two or three hours during the warmest part of the afternoon. Bring them back inside before the sun goes down.
- Days 3-5: Increase the outdoor time to five or six hours. Continue to keep them in a shaded area away from direct wind.
- Days 6-8: Allow the plants to stay outside all day. If the forecast shows a warm night (above 55°F), you can leave them out overnight for the first time.
- Day 10: Your begonias are now acclimated and ready to be planted in their permanent outdoor home.
This gradual introduction allows the plant to thicken its leaf cuticles and strengthen its stems. It ensures that when you finally transplant them into a container or garden bed, they are ready to hit the ground running.
Timing for Different Begonia Varieties
Not all begonias are exactly the same, and their timing can vary slightly depending on the type you are growing. While the general rules for warmth apply to all, some varieties are a bit more rugged than others.
Tuberous Begonias
Tuberous begonias (like the Non-Stop or Picotee series) are the most common choice for home gardeners looking for big flowers. These are the ones most likely to be started from tubers in early spring. They require the most care regarding soil temperature and are the most sensitive to late spring frosts. These are excellent for hanging baskets and shaded containers.
Wax Begonias
Wax begonias are often sold as small "bedding plants" in cell packs at garden centers. They have fibrous roots rather than tubers. These are slightly more tolerant of sun and can handle a bit more variation in temperature once established. However, they should still stay indoors until the danger of frost has passed. Because they grow quickly, you don't necessarily need to start them as early as tuberous varieties.
Rex Begonias
Rex begonias are grown primarily for their stunning, colorful foliage. They are frequently kept as houseplants year-round but can be moved outdoors to brighten up a porch in the summer. Because they are often grown for their leaves rather than flowers, they don't need a "bloom schedule," but they are still very tropical. We suggest waiting until the weather is consistently warm and humid before moving a Rex begonia outside.
Regional Timing and USDA Zones
The United States is a vast country with many different climates. The "when" for a gardener in Georgia will be very different from the "when" for someone in Maine. Understanding your USDA Hardiness Zone helps you determine your local timeline.
Zones 3 through 7
In these cooler regions, begonias are treated as annuals. You must wait until late May or even mid-June to plant outdoors. Starting your tubers indoors is highly recommended here, as it ensures you get the maximum number of weeks of bloom before the autumn cold arrives.
Zones 8 through 11
In the southern and coastal parts of the U.S., the "when" is much earlier. You can often plant begonia tubers directly into the garden as early as March or April, depending on the year. In these zones, begonias may even survive the winter if the ground doesn't freeze. However, in very hot regions (like Zone 10 or 11), the challenge isn't the cold—it's the heat. In these areas, you may want to plant even earlier so the plants can establish themselves before the intense heat of midsummer arrives.
Key Takeaway: Your local USDA zone provides a baseline, but the current year's weather is the final judge. Always check the local forecast rather than relying solely on a calendar date.
Summer Maintenance and Bloom Timing
Once your begonias are planted at the right time, you can expect them to start blooming in midsummer. Tuberous begonias typically begin their show about 12 to 14 weeks after they are first planted. If you started them indoors in March, you should see flowers by late June or July.
The "when" of maintenance is also important for a long-lasting display. Begonias are "self-cleaning" to an extent, meaning they drop their old flowers, but a little help from you can keep them looking their best.
Fertilizing Schedule
Wait until your begonias have several sets of true leaves before you start a feeding routine. Once they are established and growing well, we suggest using a balanced, water-soluble fertilizer every two weeks. This provides the consistent energy the plant needs to keep producing those large, beautiful blooms throughout the heat of the summer.
Watering by the Clock
The best time to water begonias is in the early morning. This allows any water that splashes onto the leaves to dry during the day. Begonias can be prone to powdery mildew or other fungal issues if their leaves stay wet overnight.
When you water, aim for the base of the plant. The goal is to keep the soil "evenly moist." This means it should feel like a wrung-out sponge—not soaking wet, and not bone-dry. In the peak of summer, containers may need water every day, while garden beds might only need a deep soak once or twice a week.
Fall Timing: When to Bring Them In
As the summer fades and the nights begin to cool, the begonia season starts to wind down. Just as the spring timing was about avoiding frost, the fall timing is about protecting your investment before the first freeze.
When nighttime temperatures begin to drop consistently below 50°F, the plant's growth will naturally slow down. This is the signal for the tuber to start storing energy for next year. You will notice the leaves starting to turn yellow or the stems becoming a bit soft.
Saving Your Tubers
If you want to save your tuberous begonias for next year, the timing of your harvest is key. You can wait until the first very light frost touches the foliage, but do not wait for a hard freeze that penetrates the soil. For more detail, see this guide to saving begonia tubers.
- Once the foliage has yellowed, dig up the tubers carefully.
- Cut the stems back to about an inch above the tuber.
- Lay them out in a warm, dry place for a few days to "cure" or dry out.
- Store them in a cool, dark, dry place (around 50°F) in a box of peat moss or paper bags.
By saving your tubers, you get a head start on next year's "when to plant" schedule. Larger tubers generally produce larger plants with even more flowers, so your garden will only get more beautiful with each passing year.
Troubleshooting Timing Issues
Sometimes, despite our best efforts, the timing doesn't go quite as planned. If your begonias aren't performing as expected, consider these common timing-related factors.
What if they aren't sprouting?
If you planted your tubers several weeks ago and see no signs of life, check the temperature. If the room or the soil is below 60°F, they are likely just sleeping. Move them to a warmer spot. If the soil has been very wet, gently dig one up to see if it is still firm. If it is soft or mushy, it may have rotted due to overwatering during the dormant phase.
What if they are blooming late?
If your begonias don't start flowering until August, it's usually because they weren't started early enough indoors or they didn't get enough light. Remember that while begonias love shade, they still need "bright, indirect light." Deep, dark shade will slow down flower production. Next year, try starting them two weeks earlier or moving them to a spot that gets a little more morning sun.
What if the leaves look burnt?
If you move your plants outside and the leaves turn white or brown and crispy, you may have rushed the hardening-off process or placed them in too much direct sun too quickly. This is often a timing issue of moving the plant before it was ready for the intensity of the outdoor sun. Provide extra shade and allow the plant to grow new, stronger leaves.
What to Do Next:
- Observe your plants weekly for signs of growth or stress.
- Adjust your watering and feeding as the summer heat increases.
- Take notes in a garden journal about when your first blooms appeared to help with next year's planning.
Conclusion
At Longfield Gardens, we believe that gardening should be a source of joy and relaxation. Begonias are some of the most rewarding plants you can grow because they offer so much beauty for relatively little effort. The secret is simply respecting their tropical nature and getting the timing right. By waiting for warm soil, starting your tubers early indoors, and transitioning them carefully to the outdoors, you set the stage for a spectacular summer.
- Wait for soil temperatures of 60°F before planting outside.
- Start tubers indoors 8-12 weeks before the last frost.
- Use a 10-day hardening-off period to prevent transplant shock.
- Bring tubers back inside before the first hard freeze of autumn.
"A beautiful garden is a masterpiece of timing. By following the natural rhythm of the seasons and the needs of your plants, you create a space where both the flowers and the gardener can truly thrive."
We invite you to explore the wide variety of colors and textures available in our begonia collection. Whether you are a beginner or an experienced gardener, there is always something new to discover. For high-quality tubers and the support you need to succeed, we are here to help you every step of the way.
FAQ
When should I start begonias indoors?
You should start tuberous begonias indoors about 8 to 12 weeks before the average last frost date in your area. This typically falls between late February and late March for most gardeners in the United States. Starting them early allows the plants to develop strong root systems and foliage before the outdoor growing season begins. Our begonia growing guide offers additional care details.
Can I plant begonia tubers directly in the ground?
Yes, you can plant them directly in the ground, but you must wait until the soil is at least 60°F and all danger of frost has passed. In northern climates with short summers, planting directly in the ground may result in a shorter blooming season. Starting them in pots first is usually the preferred method for the best floral display. For trailing forms, explore the Hanging Begonias collection.
What temperature is too cold for begonias?
Any temperature below 50°F is considered too cold for begonias to grow actively. While they can survive brief dips into the 40s, it often causes them to stall or drop their leaves. A frost (32°F) will damage or kill the foliage, and a hard freeze can destroy the tuber itself if it is not protected. Check the shipping information for Longfield Gardens’ zone-based timing.
When do begonias start to bloom?
Begonias typically begin blooming about 12 to 14 weeks after the tubers are first planted. If you start them indoors in March, you can expect to see flowers starting in June or July. Once they begin blooming, they will continue to produce flowers consistently until the first frost of autumn. Upright forms are available in the Upright Double Begonias collection.
