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, colorful solution for those cooler, quieter corners of your yard. Whether you are looking forward to the massive, rose-like blooms of tuberous begonias or the reliable, waxy foliage of bedding varieties, timing is the most important factor for success.
At Longfield Gardens, we want to help you make the most of every growing season. Begonias are tropical plants by nature, which means they love warmth and are very sensitive to the cold. Getting them into the ground at just the right moment ensures they grow strong and bloom vigorously from midsummer right up until the first frost of autumn.
This guide is designed for home gardeners who want to take the guesswork out of spring planting. We will cover how to monitor your local weather, why soil temperature matters more than the calendar date, and how to transition your plants safely from the indoors to the garden. By following a few simple timing rules, you can enjoy a season full of effortless, vibrant color.
The Golden Rule: Wait for the Warmth
The most important thing to remember about begonias is that they have no tolerance for frost. Because they are native to tropical and subtropical regions in Central and South America, Asia, and Africa, their cells are not built to handle freezing temperatures. Even a light, "patchy" frost can damage the tender foliage or cause the tubers to rot in the ground.
For most gardeners in the United States, the safe window to plant begonias outside begins in late spring or early summer. You should wait until the danger of frost has completely passed in your specific area. While it is tempting to plant as soon as the first sunny day arrives in April, patience is your best friend when it comes to these tropical beauties.
Waiting for the weather to settle does more than just protect the plants from freezing. Begonias that are planted in cold, damp soil often sit dormant or "pout" for weeks. When you wait until the air and soil are truly warm, the plants take off quickly and often surpass those that were put in the ground too early.
Understanding Your Local Frost Date
To know exactly when to plant begonias outside, you first need to identify your average last frost date. This date is a statistical average based on historical weather data for your specific zip code. You can find this information through local university extension offices or by looking at a hardiness zone map.
Keep in mind that an "average" date is just a guide, not a guarantee. Some years the frost lingers later than usual, while other years the warmth arrives early. A good rule of thumb for begonias is to wait about one to two weeks after your average last frost date has passed. This "buffer" period ensures that a late-season cold snap doesn't catch your new plants off guard.
If you see a forecast that predicts nighttime temperatures dipping below 50°F, it is usually best to wait a little longer. Begonias are happiest when nights are consistently in the 55°F to 60°F range. This consistency tells the plant that it is safe to start putting energy into new leaves and flower buds.
Soil Temperature: The Silent Success Factor
While we often focus on the air temperature, the temperature of the soil is actually more important for root development. Begonias, especially the tuberous varieties, need warm soil to wake up from dormancy. If the soil is below 60°F, the roots will grow very slowly, and the tuber may be susceptible to rot if the ground is also wet.
In the spring, the soil warms up much more slowly than the air. A string of 70-degree days does not necessarily mean the ground is ready for planting. You can check your soil temperature with a simple garden thermometer. Insert it about two to three inches deep in the spot where you plan to plant. If it reads 60°F or higher, your begonias will feel right at home.
For gardeners using containers, there is a bit of a "cheat code." Soil in pots, hanging baskets, and raised beds warms up much faster than the soil in the ground. This often allows you to move your container begonias outside a week or two earlier than your garden-bed begonias, provided you are ready to move the pots back into a garage or shed if a cold night is forecasted. For more container guidance, see how to plant begonia tubers in pots.
Starting Begonias Indoors for an Early Jump
If you live in a northern climate with a short growing season, you don't have to wait until June to see your first blooms. You can start begonia tubers indoors about 8 to 12 weeks before you plan to move them outside. This "head start" allows the plant to develop a strong root system and several sets of leaves while it is still too cold for them to survive outdoors.
To start tubers indoors, follow these simple steps:
- Fill a shallow tray or small pots with a light, well-draining potting mix.
- Place the tubers with the indented (concave) side facing up.
- Tuck them into the soil so they are just barely covered.
- Keep the soil lightly moist and place the tray in a warm spot with indirect light.
By the time the outdoor temperatures are safe, your indoor-started begonias will already be well on their way to flowering. This method can result in blooms appearing by Memorial Day or early June, rather than waiting until mid-July for plants started directly in the ground. For additional guidance, read how to grow begonias from bulbs.
The Importance of Hardening Off
Moving a begonia directly from a warm, cozy house or a greenhouse into the outdoor garden can be a shock to its system. Even if the temperature is perfect, the intensity of the sun and the movement of the wind are much stronger outside. To ensure a smooth transition, you should "harden off" your plants over a period of 7 to 10 days.
Hardening off is simply the process of gradually getting the plant used to outdoor conditions. On the first day, place your begonias in a sheltered, shady spot for just an hour or two, then bring them back inside. Each day, increase the amount of time they spend outside and gradually introduce them to a bit more light.
This slow introduction allows the leaves to thicken and the stems to strengthen. It also prevents "leaf scorch," which happens when the tender foliage is suddenly exposed to bright sunlight. Once your begonias can spend a full 24 hours outside without showing signs of stress, they are ready to be tucked into their permanent summer home. See this guide to hardening off begonias for a gradual schedule.
Regional Timing Considerations
Depending on where you live in the United States, your begonia planting window will vary significantly. Because we ship our bulbs and plants from our facility in New Jersey based on your specific USDA hardiness zone, you will usually receive your order right around the time it is safe to start thinking about planting. You can review the Longfield Gardens shipping information for zone-based timing details.
Northern and Coastal Regions (Zones 3-6)
In these cooler areas, spring can be unpredictable. It is not uncommon for a late frost to strike in May. Gardeners in these zones almost always benefit from starting tuberous begonias indoors in March or April. The ideal time to move them into the garden is usually late May or early June.
Central and Mid-Atlantic Regions (Zone 7)
Gardeners in this zone have a bit more flexibility. You can often plant wax begonias or start your tubers outdoors by mid-May. However, keep an eye on those spring rainstorms. Cool, heavy rain can make the ground soggy, which isn't ideal for new tubers. If the spring is particularly wet, wait for a dry spell to plant.
Southern and Desert Regions (Zones 8-11)
In the South, the challenge isn't the cold as much as it is the rapid arrival of intense heat. You can often plant begonias outside in March or April. In these regions, timing your planting early is beneficial so the plants can establish themselves before the high humidity and triple-digit temperatures of midsummer arrive.
Key Takeaway: Success with begonias is 10% planting and 90% timing. Always prioritize warm soil and frost-free nights over a specific date on the calendar.
Variety Matters: Timing Differences
While all begonias share a love for warmth, some varieties are slightly more resilient than others. Knowing which type you are planting can help you fine-tune your schedule.
Tuberous Begonias
These are the most sensitive to cold and moisture. Because the tuber acts as a storage organ, it can easily rot if the ground is cold and saturated with spring rain. These should always be the last things you plant outside. Wait until the soil feels warm to the touch. Explore the available tuberous begonia tubers for your garden.
Wax Begonias (Bedding Begonias)
Often sold in "flats" at garden centers, wax begonias are a bit more rugged. Their fibrous root systems establish quickly. While they still won't survive a frost, they tend to recover faster from a chilly night than tuberous varieties. They are great for early-season borders once the frost risk is minimal.
Rex and Rhizomatous Begonias
These are primarily grown for their stunning foliage. Since their leaves are their main attraction, you want to be extra careful with timing to avoid any cold damage that might spot or mar the beautiful patterns. Most gardeners treat these as houseplants that "vacation" outside for the summer. They should only go out when nighttime temperatures stay reliably above 60°F.
Where to Plant for Long-Term Success
Once you have determined that the timing is right, choosing the perfect spot is the next step. Begonias are the "goldilocks" of the shade garden. They don't want deep, dark shade where no light reaches, but they also can't handle the scorching afternoon sun.
The ideal location provides filtered light, such as the dappled shade found under a tall tree. Morning sun is generally fine, but the intense rays between 12:00 PM and 4:00 PM can wilt the flowers and burn the leaves. If you are planting in a very hot climate, aim for a spot that is almost entirely shaded during the heat of the day. For more guidance, see this begonia care guide.
Soil quality is the other half of the "right place" equation. We recommend using a light, loamy soil that is rich in organic matter. If your garden soil is heavy clay, it will hold too much water and stay cold too long. In this case, planting in containers or amending your garden beds with compost or peat moss is a great way to improve drainage and help the soil warm up faster in the spring.
Planting After the Wait: Depth and Spacing
When the weather finally cooperates, the physical act of planting is quite simple. For tuberous begonias, you only need to plant them about 1 inch deep. If you are planting a garden bed, space the tubers 8 to 12 inches apart. This gives the plants plenty of room to grow and ensures good air circulation, which helps prevent mildew later in the summer.
If you are planting wax begonias from nursery starts, plant them at the same depth they were in their original pots. Spacing for these is usually closer—about 6 to 8 inches—to create a dense "carpet" of color.
After planting, give them a light watering to settle the soil. Be careful not to overwater at this stage. Until the plant has several leaves, it doesn't need much moisture. As the weather warms and the plant grows larger, you can gradually increase your watering frequency. For step-by-step instructions, see how to plant begonias in the ground.
Protecting Against Late Spring Cold Snaps
Sometimes, despite our best efforts, Mother Nature throws a curveball. If you have already planted your begonias and the forecast suddenly calls for a surprise late frost, don't panic. You can easily protect your plants with a few simple items.
For begonias in the ground, you can cover them with an old bedsheet, a frost blanket, or even an upside-down plastic bucket or cardboard box. The goal is to trap the heat rising from the ground around the plant. Just remember to remove the covers the next morning once the sun comes out so the plants don't overheat.
For container begonias, the fix is even easier. Simply move the pots into a garage, a basement, or even just right up against the side of the house under an eave. This small move can make a difference of 5 to 10 degrees, which is often enough to keep the plants safe until the cold front passes.
Maintaining Your Begonias Throughout the Season
Once your begonias are established and the summer heat sets in, their needs change from "staying warm" to "staying hydrated." We suggest checking the soil moisture every few days. The goal is to keep the soil consistently damp but never waterlogged.
Feeding your begonias is also a good idea to keep the blooms coming. A balanced, water-soluble fertilizer applied every two to three weeks will provide the nutrients the plants need to produce those spectacular flowers. If you notice your plants becoming a bit "leggy" or stretched out, don't be afraid to pinch back the tips of the stems. This encourages the plant to branch out and become bushier.
Begonias are generally self-cleaning, meaning the old flowers will drop off on their own. However, removing spent blooms (deadheading) can keep the plants looking tidy and may encourage more frequent flowering. It is a rewarding, low-effort task that keeps your shade garden looking its best.
Preparing for the End of the Season
As the days grow shorter in the fall, you will notice your begonias naturally begin to slow down. Just as we timed their arrival based on the temperature, we must time their departure. Begonias will continue blooming right up until the first frost, but you should have a plan in place before the freezing weather returns.
For most gardeners, begonias are treated as annuals and can be added to the compost pile after the first frost hits the foliage. However, if you have a favorite tuberous variety, you can save the tubers to plant again next year. When the leaves turn yellow and the temperatures drop, dig up the tubers, let them dry in a cool, protected spot, and store them in a box with some peat moss or sawdust over the winter. This begonia growing guide includes additional overwintering information.
This cycle of planting, enjoying, and storing is part of what makes gardening so rewarding. Each year, you learn a little more about your yard’s unique microclimate and how to time your planting perfectly for the best results.
Conclusion
Timing is the key to a successful begonia garden. By waiting for the soil to warm to 60°F and ensuring all danger of frost has passed, you give these tropical beauties the best possible start. Whether you start your tubers indoors for a head start or wait for the natural warmth of late spring to plant directly in the ground, your patience will be rewarded with months of stunning, vibrant color in your shade garden.
At Longfield Gardens, we take pride in providing high-quality tubers and plants that are ready to thrive in your home landscape. We stand behind our quality with a guarantee that your items will arrive in prime condition and be true to their variety. If you ever have a question about timing or care, our contact team is here to support you.
What to do next:
- Identify your local average last frost date using a reliable weather guide.
- Purchase a soil thermometer to take the guesswork out of planting timing.
- If you live in a cold zone, consider starting your begonia tubers indoors this week to get a head start on the season.
FAQ
What temperature is too cold for begonias?
Begonias are very sensitive to cold and should not be exposed to temperatures below 50°F. Frost (32°F) will immediately damage or kill the foliage. For the best growth, wait until nighttime temperatures are consistently above 55°F or 60°F before moving them outside permanently.
Can I plant begonias in the sun if I plant them early?
While planting early doesn't change a begonia's light requirements, some wax begonias with darker foliage can tolerate more sun than others. However, most tuberous begonias will still need protection from the intense afternoon sun regardless of when they are planted. Always check the specific light needs of the variety you have chosen.
Do I need to water begonias immediately after planting?
Yes, you should water them lightly to help settle the soil around the roots or tubers. However, be very careful not to overwater in the first few weeks. Until the plants have established leaves to use the moisture, the soil should stay damp but not soggy to prevent the tubers from rotting.
How do I know if my soil is warm enough to plant?
The most accurate way is to use a soil thermometer and check that the temperature is at least 60°F at a depth of two to three inches. If you don't have a thermometer, a good indicator is when you see other warm-weather plants, like tomatoes or peppers, beginning to thrive in your local area.
