Introduction
There is a unique sense of excitement that comes with planning a summer garden filled with lush, tropical color. Begonias are a favorite for many of us because they offer a reliable and spectacular show from midsummer all the way until the first frost. Whether you love the massive, rose-like flowers of tuberous begonias or the delicate, waxy leaves of bedding varieties, these plants are excellent for brightening up shady corners. At Longfield Gardens, we enjoy helping you find the perfect timing to ensure your plants thrive from the moment they hit the soil. (longfield-gardens.com)
This guide is designed for home gardeners who want to take the guesswork out of the spring planting season. We will cover the specific temperature requirements begonias need, how to read your local weather patterns, and the best ways to transition these tender plants from indoors to your flower beds. For a deeper look at growing them in containers, see How to Plant Begonias in Containers. By understanding a few simple rules about timing and temperature, you can enjoy a garden full of vibrant blooms all season long. (longfield-gardens.com)
The key to success with begonias is patience, as these tropical beauties require warm air and soil before they can safely grow outdoors.
Knowing When to Move Begonias Outdoors
The most important rule for planting begonias outside is to wait until the danger of frost has completely passed. Begonias are tropical plants by nature. They have no natural defense against freezing temperatures, and even a light frost can cause significant damage to their stems and leaves. For most of the United States, this means waiting until late spring or early summer.
While the "last frost date" is a helpful guideline, it is not the only factor to consider. Begonias are sensitive to cold even if it doesn't reach the freezing point. If the weather is still damp and chilly, the plants may sit in the soil without growing, which can lead to health issues. We recommend waiting until nighttime temperatures are consistently above 50°F. If you want to be extra safe, waiting for 60°F nights will result in even faster growth.
Soil temperature is another quiet winner when it comes to timing. Even if the air feels warm, the ground often takes longer to heat up. Begonias prefer soil that has reached about 60°F. Planting in cold, wet soil can cause the tubers to stay dormant or, in some cases, rot before they even start. A simple soil thermometer can help you decide if the ground is ready for your plants.
Key Takeaway: Always prioritize nighttime temperatures over the calendar date. If the nights are still dipping below 50°F, it is better to keep your begonias protected for another week or two.
Understanding the Role of Hardiness Zones
Your USDA hardiness zone plays a major role in when we ship your order and when you should begin thinking about your garden layout. For zone-based timing and shipping help, see Shipping Information. Begonias are generally considered tender perennials, which means they can stay in the ground year-round only in very warm climates like zones 9 through 11. In these areas, you may be able to plant as early as March or April. (longfield-gardens.com)
For gardeners in zones 3 through 8, begonias are typically grown as annuals or brought indoors for the winter. In these northern and central regions, the planting window usually opens between Mother's Day and mid-June. Because every year brings different weather patterns, it is helpful to keep an eye on your local forecast rather than sticking to a specific date every year.
Starting Begonias Indoors for an Early Head Start
If you live in a region with a short growing season, you do not have to wait for the outdoors to warm up before you begin. Starting begonia tubers indoors is a wonderful way to get a jump on the season. This process allows the plants to develop strong root systems and several inches of growth before they ever touch the garden soil.
We recommend starting your tubers indoors about 8 to 12 weeks before your average last frost date. For many people, this means starting in late February or March. This timing ensures that by the time June arrives, your begonias are already robust and perhaps even beginning to show their first flower buds.
To start them indoors, follow these simple steps:
- Fill a shallow tray or individual pots with a high-quality, moist potting mix.
- Place the tubers with the indented (concave) side facing up. This is where the sprouts will emerge.
- Tightly tuck them in but do not bury them deeply; a light covering of half an inch of soil is sufficient.
- Keep the pots in a warm room (about 70°F) with bright, indirect light.
- Water sparingly at first, only enough to keep the soil from drying out completely.
Starting early is a rewarding way to see color in your garden by Memorial Day or early June. It turns the wait for spring into an active and enjoyable part of your gardening hobby.
How to Transition Your Begonias Outside
Once the weather is warm enough, you might feel tempted to move your begonias directly from your warm house into the garden. However, a sudden change in environment can be a shock to the plants. This is where "hardening off" becomes essential. Hardening off is simply the process of gradually getting your plants used to the wind, sun, and temperature swings of the outdoors. If you are growing them in a pot, Can You Plant Begonias in a Pot? is a helpful companion guide. (longfield-gardens.com)
The best time to start this transition is about 10 days before you plan to plant them permanently. Start by placing your pots in a shaded, protected spot outside for just two or three hours during the warmest part of the day. Bring them back inside before the sun goes down.
Over the next week, slowly increase the amount of time they spend outside. You can also gradually move them into slightly more light, though you should always avoid harsh, direct afternoon sun. This slow introduction helps the leaves toughen up and prepares the stems to handle the breeze. If a surprise cold snap is predicted during this window, simply keep the plants indoors until the weather improves.
What to do next:
- Check the 10-day forecast for any overnight lows below 50°F.
- Identify a sheltered spot on a porch or under a tree for the transition.
- Begin the move-out process on a calm, overcast day if possible.
- Monitor the soil moisture, as pots dry out faster outdoors than they do inside.
Selecting the Right Location for Your Begonias
Timing your planting correctly won't matter as much if the location doesn't meet the plant's needs. Begonias are famous for their love of shade, but "shade" can mean different things. Most begonias thrive in filtered light, such as the dappled sunlight found under tall trees or on a covered patio. For more detail on light and soil preferences, see Where Do Begonias Like to Be Planted?. (longfield-gardens.com)
Avoid spots that receive intense, direct sunlight between noon and 4:00 PM. This mid-afternoon sun is often too hot and can scorch the delicate leaves. However, morning sun is usually very beneficial and can help encourage more blooms. If you notice your begonias have lots of leaves but very few flowers, they might actually need a little more light.
Drainage is the other critical factor for your planting site. Begonias do not like to have "wet feet," which means their roots should not sit in standing water. If you have heavy clay soil that stays soggy for hours after a rain, consider planting in raised beds or containers. Adding organic matter like compost can also help improve the soil structure and drainage.
Planting Your Begonias Outside
When the "when" and "where" are settled, it is finally time to plant. Whether you are using containers or planting directly into your landscape, the process is straightforward and satisfying.
Planting in the Garden
For garden beds, loosen the soil to a depth of about six inches. If you are planting started begonias, dig a hole that is twice as wide as the root ball and just as deep. Place the plant in the hole so the top of the root ball is level with the surrounding soil. Space your plants about 8 to 12 inches apart to allow for good air circulation, which helps prevent mildew.
Planting in Containers
Begonias are some of the best plants for pots and hanging baskets. If you want a step-by-step walkthrough for containers, How to Plant Begonias in Containers covers the process in detail. Use a high-quality potting mix rather than garden soil, as potting mix is designed to drain well and provide the light texture begonias love. Make sure your container has drainage holes. If you are planting tubers directly into a pot, follow the same "indented side up" rule and cover with about an inch of mix. (longfield-gardens.com)
Initial Watering
After planting, give your begonias a gentle but thorough watering. This helps settle the soil around the roots and removes any large air pockets. Be careful not to over-water during the first few weeks. The plants are still establishing their root systems and cannot drink as much water as they will later in the summer.
Caring for Your Begonias Throughout the Season
Once your begonias are established in their outdoor home, the goal shifts to maintaining their beauty. Successful begonia care is all about consistency. These plants appreciate a steady environment without extreme swings in moisture or nutrients.
Watering Correctly
The best way to water begonias is to soak the soil deeply and then let the top inch or two dry out before watering again. This "deep, then dry" method encourages the roots to grow further down into the soil. Avoid splashing water directly onto the leaves, as wet foliage in the shade can sometimes lead to fungal issues. Watering in the morning is ideal, as it gives any stray droplets time to evaporate before evening.
Fertilizing for Blooms
Begonias are heavy feeders. They put a lot of energy into producing those large, colorful flowers, and they need fuel to keep going. We recommend using a balanced, water-soluble fertilizer every two weeks during the growing season. If you prefer, you can use a slow-release granular fertilizer at planting time, which will provide a steady stream of nutrients over several months.
Maintenance and Deadheading
One of the best things about many modern begonia varieties is that they are "self-cleaning," meaning the old flowers fall off on their own. However, if you are growing tuberous begonias, you may want to occasionally remove spent blooms to keep the plant looking tidy. This also prevents the old flowers from resting on the leaves, which can sometimes cause rot in very humid weather.
Preparing for Fall
As the summer winds down, the timing of your garden chores becomes important again. Just as begonias are the last to go out in the spring, they are often the first to come in during the fall. You should begin preparing to protect or move your begonias before the first frost is predicted.
If you live in a cold climate and want to save your tuberous begonias for next year, stop fertilizing in late August. This signals to the plant that it is time to start storing energy in the tuber. When the leaves begin to turn yellow or after the very first light frost blackens the foliage, it is time to dig them up.
Gently lift the tubers from the ground, cut the stems back to about an inch, and let the tubers dry in a cool, shaded spot for a few days. Once they are dry to the touch, you can store them in a box filled with peat moss or sawdust. Keep them in a cool, dark place (around 50°F) until next spring. This cycle of rest and growth is what allows begonias to provide beauty for many years.
Key Takeaway: The end of the season is just as important as the beginning. Bringing your plants in before a hard freeze ensures you can enjoy them again when the warm weather returns.
Conclusion
Finding the right time for when to plant begonias outside is one of the most important steps toward a successful gardening season. By waiting for warm nights and taking the time to harden off your plants, you set the stage for a summer filled with vibrant, healthy growth. Gardening is a journey that rewards patience, and waiting for that perfect window of warm weather is always worth it.
We at Longfield Gardens are proud to provide the high-quality tubers and perennials that help make your garden a success. If you want to browse the full selection again, return to the Begonia Flower Bulbs for Sale collection. Remember that while rules about temperature and frost are helpful, your own observations of your backyard’s microclimate are your best tool. (longfield-gardens.com)
- Wait for nighttime temperatures to stay above 50°F–60°F.
- Start tubers indoors 8–12 weeks early for a head start.
- Hardens off your plants for 7–10 days before permanent planting.
- Choose a spot with filtered light and excellent drainage.
We hope you enjoy the process of watching your begonias grow and bloom. If you are ready to start your next garden project, we invite you to explore our selection of premium begonias to find the perfect colors for your home.
FAQ
Can begonias survive a light frost if I cover them?
While a light frost might not kill the entire plant if it is covered with a frost blanket, it is very risky. Begonias have high water content in their stems, making them very susceptible to cell damage from freezing. It is always safer to wait until the frost danger has completely passed or to move containers into a garage or shed for the night.
What happens if I plant my begonias too early?
If begonias are planted when the soil or air is still cold (below 50°F), they often experience stunted growth. The leaves may turn yellow or translucent, and the plant may become more susceptible to root rot because it isn't active enough to use the water in the soil. Patience is rewarded with much faster growth once the weather truly warms up.
Do different types of begonias have different planting times?
Generally, all begonias share the same sensitivity to cold. Tuberous, wax, and rex begonias all prefer the same warm conditions. However, wax begonias are sometimes slightly more tolerant of varying light conditions, whereas tuberous begonias are the most sensitive to high heat and direct afternoon sun. Their "when to plant" window remains the same regardless of the variety. For more background on the plant family, see All About Begonias. (longfield-gardens.com)
How do I know if my soil is warm enough to plant?
The easiest way is to use a soil thermometer, which you can find at most garden centers. Insert it about four inches into the ground. If the temperature consistently reads 60°F or higher in the morning, your soil is ready. If you don't have a thermometer, a good rule of thumb is that if the deciduous trees in your area have fully leafed out, the soil is usually warm enough for tropicals.
