Table of Contents
- Introduction
- The Importance of Soil and Air Temperature
- Understanding Your USDA Hardiness Zone
- Starting Begonias Indoors for an Earlier Show
- The Hardening Off Process
- Factors That Influence Your Planting Date
- Choosing the Right Spot: Sun and Wind Considerations
- Preparing the Soil for Planting
- How to Plant Begonias Out in the Garden
- Caring for New Transplants
- Common Timing Questions and Scenarios
- Realistic Expectations for Your Begonia Garden
- Conclusion
- FAQ
Introduction
There is a unique sense of excitement that comes with planning a shade garden. While many flowering plants crave the intense heat of the midday sun, begonias offer a refreshing alternative, bringing vivid colors and lush textures to those quiet, cooler corners of the yard. At Longfield Gardens, we enjoy helping gardeners transform these shadowed spaces into vibrant retreats with our selection of premium tubers and plants.
The most common question we hear from gardeners eager to start their season is about timing: when can I plant out begonias? Because these plants are tropical by nature, they have a specific set of needs when it comes to temperature and light. Getting the timing right is one of the easiest ways to ensure your garden remains in bloom from midsummer all the way through the first frost of autumn.
In this guide, we will explore the ideal temperature windows for planting, how to transition your plants from indoors to out, and the simple indicators that tell you the soil is ready. Whether you are growing upright tuberous varieties in garden beds or trailing types in hanging baskets, understanding the "when" of planting is your first step toward a successful season.
The Importance of Soil and Air Temperature
The most important rule for planting begonias is to wait for the warmth. These plants are native to tropical and subtropical regions in Central and South America, Asia, and Africa. Because of this heritage, they do not have a biological "antifreeze" to protect them from cold weather. Patience is a gardener's best friend when it comes to these spectacular bloomers.
For begonias to thrive, you should wait until the danger of frost has completely passed. However, "no frost" is only the minimum requirement. For the best performance, wait until the nighttime temperatures are consistently staying above 50°F (10°C). If the nights are still dipping into the 40s, the plants may survive, but their growth will often stall, and they may take several weeks to recover once the weather finally warms up.
Soil temperature is just as critical as air temperature. We recommend waiting until the soil feels warm to the touch, ideally reaching about 60°F (15°C). Cold, damp soil can cause tubers to sit dormant for too long, which increases the risk of the tuber becoming soft or failing to sprout. A simple way to check this without a thermometer is to observe other plants in your landscape; when your tomatoes and peppers are ready to go into the ground, your begonias usually are, too.
Understanding Your USDA Hardiness Zone
To determine your specific planting window, it helps to know your USDA hardiness zone. We use these zones to time our shipments so that your order arrives roughly two weeks before the ideal planting time for your region; our shipping information page explains the details.
In the United States, begonias are typically grown as annuals in zones 3 through 8. In these areas, they must be planted fresh each spring or overwintered indoors. In warmer climates, specifically zones 9 through 11, begonias can often stay in the ground year-round as perennials, provided the soil remains well-drained and does not freeze.
If you live in a northern state like Michigan or Maine, your planting out date might not arrive until early to mid-June. Conversely, gardeners in Georgia or Texas may find they can move their plants outdoors as early as late March or April. Always keep an eye on your local long-range forecast rather than relying strictly on a calendar date, as spring weather can be unpredictable.
Starting Begonias Indoors for an Earlier Show
If you want to enjoy flowers as early as possible, starting your begonia tubers indoors is a fantastic strategy; All About Begonias covers the basics.
We suggest starting your tubers indoors about 8 to 12 weeks before your area’s average last frost date. This usually means planting them in small pots or trays in late February or March. By the time the outdoor temperatures are safe, you will have a well-established plant ready to burst into bloom.
Steps for Indoor Starting
- Choose the right container: Use a shallow tray or individual small pots with excellent drainage holes.
- Position the tuber correctly: Look for the indented or "hollow" side of the tuber. This side should face up, as this is where the sprouts will emerge.
- Light and Water: Place the containers in a warm spot with bright, indirect light. Water very sparingly at first—just enough to keep the soil from drying out completely.
- Wait for sprouts: It can take 2 to 4 weeks for the first green tips to appear. Once they do, you can slightly increase watering, but never let the soil become soggy.
Key Takeaway: Starting begonias indoors in early spring gives you a 2-month head start on the growing season, often resulting in flowers by Memorial Day.
The Hardening Off Process
When you have a plant that has been pampered indoors, you cannot move it directly into the garden without a transition period. This process is called hardening off. Even though begonias love the shade, the intensity of outdoor light and the movement of the wind are much stronger than what they experience inside a home.
Start by placing your begonias in a sheltered, fully shaded spot for just an hour or two during the warmest part of the day. Over the course of 7 to 10 days, gradually increase the amount of time they spend outside and the amount of light they receive.
During this time, keep a close watch on the weather. If a sudden cold snap or heavy rainstorm is predicted, bring the plants back inside. This gradual introduction helps the plant's cell walls thicken and prevents "leaf scorch," which looks like bleached or papery spots on the foliage. Once the plants can spend a full night outdoors without drooping, they are ready for their permanent home.
Factors That Influence Your Planting Date
While the general rule is "after the last frost," several environmental factors might lead you to adjust your timing by a week or two.
Microclimates in Your Yard
Every yard has microclimates—areas that are slightly warmer or cooler than the surrounding environment. A covered porch or a spot near a brick wall that absorbs daytime heat will stay warmer at night than an open garden bed in the middle of the lawn. If you are planting in large decorative pots, the soil will reach that target 60°F temperature sooner than the deep soil in a garden border, and the summer flowers for shade collection offers more container-friendly ideas.
Type of Begonia
While all begonias prefer warmth, some are slightly more rugged than others.
- Wax Begonias: Often sold in cell packs, these are quite resilient and can handle a bit more sun and fluctuating temperatures once established.
- Tuberous Begonias: These produce the largest, most spectacular flowers but are also the most sensitive to cold and wind. They should be the last ones moved outdoors.
- Rex Begonias: Primarily grown for their stunning foliage, these are very sensitive to humidity and temperature drops and should stay indoors until the air is consistently balmy.
Container vs. In-Ground Planting
Containers warm up much faster than the ground in the spring. If you are planting in large decorative pots, the soil will reach that target 60°F temperature sooner than the deep soil in a garden border. However, remember that containers also cool down faster at night. If a late-season chill is predicted, container-grown begonias are much easier to protect because you can simply slide them into a garage or shed for the night.
Choosing the Right Spot: Sun and Wind Considerations
The "when" of planting is only half the battle; the "where" is just as important. Begonias are famous for their ability to bloom in the shade, but "shade" can mean different things.
Most begonias do best in filtered light or dappled shade. Imagine the light under a tall tree where the sun peeks through the leaves. If a spot is too dark, the plants will become "leggy," meaning they grow tall and spindly as they stretch for light, and they will produce fewer flowers. Conversely, intense afternoon sun can wilt the stems and burn the leaves. A spot that gets gentle morning sun and afternoon shade is often the "sweet spot" for most varieties.
Wind protection is another vital factor. Begonias, particularly the upright tuberous varieties, have very brittle stems. A strong gust of wind can easily snap a stem laden with heavy blooms. When you are deciding where to plant out, look for areas that are sheltered by a fence, a hedge, or the side of your house. If you are planting in hanging baskets, ensure they are hung securely and are not in a wind tunnel between buildings.
Preparing the Soil for Planting
Before you move your plants out, take a moment to prepare the soil. This ensures that the roots can expand easily and that water moves through the soil at the right pace.
"Drainage" is a word gardeners use a lot, and it simply refers to how fast water leaves the soil. Begonias love moisture, but they hate sitting in "wet feet." If the soil stays saturated, the tuber can rot. To improve drainage in garden beds, you can mix in some organic matter like compost or finely ground bark. This loosens the soil and adds nutrients at the same time.
If you are planting in containers, always use a high-quality potting mix rather than garden soil. Garden soil is too heavy for pots and will pack down, preventing air from reaching the roots. Look for a mix that contains peat moss or perlite, which helps keep the soil light and airy.
Checklist for Planting Out
- Check the 10-day forecast for nighttime lows below 50°F.
- Confirm the soil is warm (60°F) and well-draining.
- Ensure the planting site is protected from harsh winds.
- Have your "hardening off" plan completed.
- Prepare your containers with fresh potting mix.
How to Plant Begonias Out in the Garden
Once the weather is perfect and your plants are hardened off, it is time for the final move. Whether you are transplanting a started plant or putting a dormant tuber directly into the ground, the process is simple and rewarding.
Planting Tubers Directly
If you live in a warm climate or choose not to start tubers indoors, you can plant tuberous begonias directly outside. Dig a shallow hole and place the tuber with the hollow side facing up. Cover it with only about one inch of soil. Planting too deep is a common mistake; keeping them near the surface ensures they get the warmth they need to wake up. Space them about 8 to 12 inches apart to allow for airflow, which helps prevent mildew later in the season.
Transplanting Started Plants
If you are moving a plant from a pot into the ground, dig a hole that is twice as wide as the root ball but no deeper. You want the base of the stems to be level with the surrounding soil. Gently tease the roots if they have started to circle the inside of the pot, then set the plant in the hole. Fill in with soil and press down very gently with your hands—begonias have delicate roots, so there's no need to "stomp" the soil down.
Initial Watering
Immediately after planting, give your begonias a gentle drink of water. This helps settle the soil around the roots and removes any large air pockets. Be careful not to drench them; you want the soil to be moist like a wrung-out sponge, not a swamp.
Key Takeaway: Proper spacing and shallow planting are the quiet winners of begonia gardening, ensuring the plants have enough room to breathe and grow.
Caring for New Transplants
The first two weeks after planting out are the most critical. This is the time when the plant is establishing its roots in its new home.
Watering Correctly
Watering is less about a strict schedule and more about observing the soil. The "deep, then let it dry" method works best. Stick your finger an inch into the soil; if it feels dry, it is time to water. If it still feels damp, wait a day. Because begonias are often in the shade, the soil doesn't dry out as fast as it does in the sun. Over-watering is a much more common issue than under-watering.
Feeding for Flowers
To keep the blooms coming all summer long, begonias appreciate a little extra nutrition. We recommend using a balanced, water-soluble fertilizer. You can start fertilizing once you see active new growth after transplanting. A common approach is to use a half-strength solution every two weeks. This provides a steady stream of nutrients without overwhelming the plant.
Mulching
In garden beds, a thin layer of mulch can be very helpful. It helps keep the soil temperature consistent and prevents water from splashing up onto the leaves, which can sometimes carry soil-borne diseases. Just be sure to keep the mulch an inch or two away from the base of the stems to prevent rot.
Common Timing Questions and Scenarios
Sometimes, despite our best plans, the weather doesn't cooperate. Here are a few common scenarios gardeners face.
"The forecast suddenly shows a night at 38°F, but my begonias are already in the ground." Don't panic! If your begonias are in the ground, you can cover them with a frost blanket, an old bedsheet, or even a cardboard box for the night. This traps the warmth from the soil and protects the foliage. Just remember to remove the cover in the morning once the sun comes up.
"My tubers haven't sprouted yet and it's already June." If the soil has been unusually cold or wet, tubers can be slow to wake up. As long as the tuber feels firm like a potato and isn't soft or mushy, it is likely just waiting for more heat. One change you can make is to move container-grown begonias to a slightly sunnier (but still protected) spot for a few hours a day to help warm the soil.
"I bought begonias at the garden center, but they were in a greenhouse." Plants grown in commercial greenhouses are very "soft." They have been grown in perfect, windless, humid conditions. These plants need an even longer hardening-off period than the ones you grow in your own home. Treat them with extra care for the first two weeks.
Realistic Expectations for Your Begonia Garden
Gardening is a partnership with nature, and while we can provide the best possible start, the weather will always have the final say. A cool, rainy summer might result in slower growth and fewer blooms, while a warm, humid summer is exactly what begonias love.
It is also normal for tuberous begonias to produce two different types of flowers on the same plant. They produce "male" flowers, which are the large, showy doubles, and "female" flowers, which are smaller and single. If you see a mix of flower shapes, your plant is perfectly healthy!
We stand behind the quality of our tubers at Longfield Gardens. We work with trusted growers in regions like Holland to ensure that when your order arrives at our facility in Lakewood, New Jersey, it is in prime condition. If you ever have a concern about the quality of your items upon arrival, we encourage you to reach out to our team so we can make it right. Our 100% quality guarantee is our way of ensuring you feel confident as you start your gardening journey.
Conclusion
Knowing when to plant out begonias is the secret to a stress-free and beautiful shade garden. By waiting for consistent nighttime temperatures above 50°F and soil temperatures near 60°F, you give these tropical beauties the warm welcome they need to thrive. Whether you start them early indoors or plant them directly in the spring soil, your patience will be rewarded with a spectacular display of color that lasts until the first frost of autumn.
- Wait for nighttime temperatures to stay consistently above 50°F.
- Ensure the soil is warm and well-draining before planting.
- Harden off indoor-started plants for 7–10 days.
- Choose a sheltered spot with dappled or morning sun.
"The beauty of begonias lies in their ability to turn the quietest, shadiest corners of the landscape into a masterclass of color and form."
Your next step is to choose the varieties that speak to you. From the giant blooms of the Americana series to the graceful drapes of cascading varieties, there is a begonia for every gardener. Visit our website to explore our planting guides and find the perfect additions for your home this season.
FAQ
Can begonias survive a light frost if I plant them too early?
Tuberous begonias are very sensitive to cold and generally will not survive a frost. Even temperatures slightly above freezing can cause the leaves to turn black and the stems to collapse. If a surprise frost is predicted after you have planted, it is essential to cover your plants with a cloth or move containers indoors to protect them.
Is it better to plant begonias in pots or directly in the ground?
Both options work well, but pots offer more control. In a container, you can use a specific potting mix for perfect drainage and move the plant easily if the weather turns cold or the sun is too intense. Planting in the ground is great for mass displays, provided your soil is loose, rich, and doesn't hold standing water.
How do I know if my soil is warm enough to plant out?
A simple way to tell if the soil is ready is to look at the surrounding environment. If the grass is growing vigorously and other warm-season plants like impatiens or tomatoes are thriving, the soil is likely around 60°F. You can also use a basic soil thermometer; check the temperature in the morning about two inches deep for the most accurate reading.
Why are my begonia leaves turning yellow after I moved them outside?
Yellowing leaves shortly after moving outdoors is often a sign of "transplant shock" or too much water. If the soil is very wet, allow it to dry out for a few days. If the plant was moved too quickly from a dark indoor room to a bright outdoor spot, it might just be adjusting to the light. Ensure the plant is in a sheltered, shaded area while it acclimates.