When Is the Best Time to Plant Begonias Outside?

Table of Contents

1. Introduction
2. The Fundamental Rule: Frost and Warmth
3. Timing for Tuberous Begonias
4. Timing for Wax and Bedding Begonias
5. The Importance of Soil Temperature
6. Transitioning Begonias: The Hardening Off Phase
7. Regional Timing Across the United States
8. Signs It Is Still Too Early
9. Creating the Ideal Outdoor Environment
10. Extending the Season: Fall Considerations
11. Conclusion
12. FAQ

Introduction

There is a special kind of excitement that comes with planning a shade garden, and begonias are often the stars of the show. With their lush, colorful foliage and blossoms that look like miniature roses or camellias, these plants bring a tropical flair to any corner of the yard. At Longfield Gardens, we enjoy how begonias provide a continuous display of color from the moment they are planted until the first frost of autumn. Whether you are looking to fill hanging baskets, patio containers, or garden beds, getting the timing right is the first step toward a successful season.

Knowing exactly when to move these tender plants into the open air is a common question for gardeners of all experience levels. Because begonias are native to warm, tropical climates, they are quite sensitive to the cold. This article will explain the best time to plant begonias outside based on your local weather, the specific type of begonia you are growing, and the condition of your soil. If you need help matching those conditions to your area, the hardiness zone map is a useful place to start. We will help you identify the perfect window for planting so your garden can thrive all summer long.

The most important thing to remember is that begonias love warmth and need to stay protected until the spring weather is truly settled.

The Fundamental Rule: Frost and Warmth

The single most important rule for planting begonias is to wait until the danger of frost has completely passed. Begonias are not frost-tolerant plants. Even a light, "patchy" frost can damage the leaves, and a hard freeze will likely kill the plant or the tuber. While it might be tempting to plant on the first warm day of April, it is better to wait until you are certain the cold nights are over.

In most parts of the United States, this means waiting until late spring or even early summer. The "average last frost date" provided by local weather services is a helpful guideline, but it is just an average. We recommend keeping an eye on the ten-day forecast. If the nighttime temperatures are still dipping into the 40s, it is usually best to keep your begonias protected for a little longer.

Begonias do their best growing when the air and soil are consistently warm. They essentially go into a holding pattern when the weather is chilly. By waiting for the right conditions, you aren't "losing" time; you are ensuring that once the plants go into the ground, they have the energy and environment they need to take off immediately.

Timing for Tuberous Begonias

Tuberous begonias are a favorite for many of our customers because of their massive, ruffled blooms and variety of growth habits. For upright displays, the Upright Double Begonias collection is a good fit. These plants grow from a thickened underground stem called a tuber. Because these tubers take a little while to "wake up" and begin growing, the timing for these is slightly different than for other types.

Starting Tubers Indoors

If you want to see blooms as early as possible, the best time to start tuberous begonias is indoors, about 8 to 12 weeks before your last expected frost. For step-by-step guidance, see How to Plant Begonias for a Stunning Shade Garden. This head start allows the plant to develop a strong root system and several sets of leaves before it ever touches outdoor soil.

In most regions, this means starting your tubers in February or March. Place them in a warm, bright spot inside your home. By the time the outdoor temperatures are safe, your begonias will already be well-established and ready to flower much sooner than if you had waited to plant the dry tubers directly in the garden.

Moving Started Plants Outside

Once your indoor plants are lush and green, you still must wait for the outdoor environment to be hospitable. Even if the plants look ready to go, the air must be warm. We suggest waiting until nighttime temperatures are consistently above 50°F and ideally closer to 60°F. Moving a plant from a cozy 70°F house into a 45°F night can cause significant stress, even if there isn't a frost.

Direct Planting of Tubers

If you prefer to plant your tubers directly into the garden or outdoor containers, you must wait until the soil itself has warmed up. This usually happens a few weeks after the last frost. In the northern half of the US, this is often late May or early June. Planting a dormant tuber into cold, wet soil in early May is a common mistake that can lead to the tuber rotting before it ever has a chance to sprout.

Key Takeaway: For tuberous begonias, start indoors in late winter for the earliest blooms, but do not move them outside until the nights are reliably warm.

For more spring-planted options, browse Shop Spring-Planted Summer-Blooming Bulbs.

Timing for Wax and Bedding Begonias

Wax begonias are the workhorses of the shade garden. They are fibrous-rooted plants usually grown as annuals and are widely available at nurseries and garden centers in the spring. Because these are typically sold as active, blooming plants, the timing for planting them is very specific.

The best time to plant wax begonias is after the soil has warmed to at least 60°F. Because these plants are already in an active growth stage when you buy them, they are very sensitive to cold "shocks." If you plant them while the ground is still chilly, the leaves may turn a reddish-bronze color—a sign of stress—and the plant may stop growing for several weeks.

If you are shopping for container-friendly choices, Summer Blooming Bulbs for Containers is a useful place to browse. For gardeners in middle-latitude states (Zones 6 and 7), this usually means the middle to the end of May. In more northern zones (Zones 3, 4, and 5), the first week of June is often the safest bet. It is always better to keep your nursery flats on a porch or in a garage for an extra week than to rush them into cold garden soil.

The Importance of Soil Temperature

We often talk about air temperature, but soil temperature is actually the "secret" to begonia success. Begonias have relatively delicate root systems. When those roots are placed in soil that is cold and saturated with spring rain, they cannot function properly. They struggle to take up nutrients, and the plant essentially sits in a dormant state, making it vulnerable to pests and diseases.

For a broader look at begonia types and care, see All About Begonias. A simple way to check if the time is right is to use a basic soil thermometer. You are looking for a consistent reading of 60°F at a depth of about 4 inches. If you don't have a thermometer, a good rule of thumb is to wait until you are comfortable wearing a light t-shirt outside for most of the day. If the ground feels cold to the touch when you dig a hole, it is likely too early for your begonias.

Improving Soil Conditions for Earlier Planting

If you are eager to get started and the weather is mostly warm but the soil is still a bit damp and cool, you can take a few steps to speed things along:

• Use Raised Beds: Soil in raised beds warms up much faster than the ground.
• Container Gardening: Pots and hanging baskets are the easiest way to enjoy begonias early in the season. If your garden is especially shady, our Summer Flowers for Shade collection is another natural next step.
• Mulch Later: Wait to apply mulch until the soil has fully warmed up. Mulch acts as an insulator; if you apply it over cold soil, it will keep that soil cold for a longer period.

Transitioning Begonias: The Hardening Off Phase

Timing isn't just about the calendar date; it's also about the transition process. If you have been growing your begonias indoors or if you just brought them home from a warm, humid greenhouse, you cannot move them directly into the garden. This transition period is called "hardening off," and it usually takes about 7 to 10 days.

If you are still deciding where begonias fit best in your landscape, Are Begonias Shade Plants? is a helpful companion guide. The best time to start the hardening off process is when the daytime temperatures are consistently in the 60s.

1. Day 1-2: Place your begonias in a fully shaded, protected spot (like a covered porch) for just 2 to 3 hours in the afternoon, then bring them back inside.
2. Day 3-4: Increase their outdoor time to 5 or 6 hours. Make sure they are protected from strong winds, which can easily snap their brittle stems.
3. Day 5-7: Leave the plants out all day. If the nighttime temperatures are staying above 55°F, you can begin leaving them out overnight.
4. Day 8-10: Your begonias are now acclimated to the outdoor humidity, light levels, and breezes. They are ready to be planted in their permanent summer home.

By including this week of transition in your planning, you ensure that the "best time to plant" is a time when the plant is actually ready to handle the elements. This prevents leaf scorch and transplant shock, leading to a much more beautiful display.

Regional Timing Across the United States

Because the US covers so many different climates, the "best time" varies significantly by region. While local conditions can change year to year, here is a general guide for when to move begonias outside:

Southern States (Zones 8-11)

In the warmest parts of the country, begonias can often go outside in March or early April. In South Florida and parts of South Texas, they are often used as winter interest plants because the summer heat can actually be more stressful for them than the winter. If you live in these areas, your goal is to get them established before the intense heat of mid-summer arrives.

Central and Mid-Atlantic States (Zones 6-7)

For gardeners in places like Virginia, Kentucky, or Missouri, the ideal window usually opens in early to mid-May. This is the region where "Mother's Day" is the traditional benchmark for planting tender annuals, and it usually holds true for begonias as well.

Northern States and High Altitudes (Zones 3-5)

In the North, patience is a virtue. It is common to have a late frost in mid-May, so the best time to plant begonias outside is typically late May or the first week of June. For order timing, our Shipping Information page explains how shipping is scheduled by zone. Because the growing season is shorter here, we highly recommend starting tuberous begonias indoors in March to ensure you get a full season of flowers.

Pacific Northwest

The PNW has a unique climate where it stays cool and damp for a long time. Even though it may not freeze, the soil remains cold. Wait until the "June Gloom" begins to break and you see consistent sunshine to warm the earth.

What to do next:

• Check your local "average last frost date."
• Monitor your local ten-day forecast for night temperatures above 50°F.
• Purchase a soil thermometer to check for 60°F ground temperature.
• Prepare your containers or garden beds with well-draining soil.

Signs It Is Still Too Early

If you aren't sure if it's time to plant, the plants themselves (or the ones already in the neighborhood) will tell you. Here are a few signs that you should wait another week:

• Yellowing Foliage on Other Plants: If you see other tender plants in the neighborhood looking pale or yellow, the soil is likely too cold.
• The "Oak Leaf" Rule: Many old-time gardeners wait until oak leaves are the size of a squirrel's ear before planting tender flowers. This is a natural indicator that the environment has warmed up.
• Cold Toes: If you walk outside barefoot and the ground feels uncomfortably cold, it is too cold for begonia roots.
• Heavy Spring Rains: If the ground is "mucky" or holds water when you step on it, wait. Planting in waterlogged soil is a recipe for root rot.

Creating the Ideal Outdoor Environment

Once the timing is right and you are ready to plant, choosing the right spot will help your begonias make the most of the warm weather. Most begonias prefer a location with filtered light or morning sun and afternoon shade. The hot, direct afternoon sun can be too intense and may wilt the flowers or burn the leaves.

The soil should be rich and, most importantly, well-draining. We recommend amending your garden soil with compost or leaf mold to create a light, airy texture. This allows the begonia roots to spread easily and ensures that excess water can move away from the plant. If you are planting in containers, always use a high-quality potting mix and ensure the pots have plenty of drainage holes. For trailing displays, the Hanging Begonias collection is worth a look.

When you plant, keep the depth in mind. For tuberous begonias that you have started indoors, plant them so the top of the root ball is level with the surrounding soil. For wax begonias, plant them at the same depth they were in their nursery pots. A quick watering right after planting will help settle the soil and get the roots off to a great start.

Extending the Season: Fall Considerations

The "best time" to have begonias outside ends when the temperatures begin to drop in the fall. Just as they dislike the cold of early spring, they will begin to struggle when the crisp autumn air arrives.

When nighttime temperatures start dipping back into the 50s, the growth will slow down. This is actually the time when tuberous begonias begin to store energy back into their tubers for the next year. You can leave them out until the first light frost kills the foliage, but do not let the tubers freeze in the ground.

For wax and Rex begonias, if you wish to keep them as houseplants, you should move them indoors while the windows are still open and the indoor/outdoor temperatures are similar. This makes the transition much easier for the plant.

Conclusion

Timing is the key to a vibrant, blooming begonia display. By waiting for the soil to warm to 60°F and ensuring the danger of frost has completely passed, you give your plants the best possible foundation for success. Whether you start your tubers early indoors or pick up fresh wax begonias from a local nursery, remember that patience in the spring pays off with a spectacular show all summer.

At Longfield Gardens, we want your gardening experience to be as rewarding and enjoyable as possible. Begonias are one of the most versatile and beautiful plants you can add to your landscape, and once the weather is right, they are incredibly easy to care for.

• Wait for the soil to reach 60°F.
• Confirm that the last frost has passed.
• Harden off indoor plants for 7-10 days.
• Plant in well-draining soil with afternoon shade.

"The secret to a beautiful begonia garden isn't a special fertilizer or a complicated trick; it is simply matching the plant's tropical needs to the natural rhythm of your local spring weather."

We invite you to explore the many varieties of begonias we offer and start planning your most colorful shade garden yet.

FAQ

Can I plant begonias outside if it is still 40 degrees at night?

It is best to wait. While 40 degrees may not freeze the plant, begonias are tropical and will stop growing in such cold temperatures. This stress can make them more susceptible to disease and slow down their blooming later in the summer. We recommend waiting until nights are consistently 50°F or warmer.

What happens if I plant my begonia tubers too early?

If tubers are planted in cold, wet soil before they have sprouted, they are at a high risk of rotting. The dormant tuber cannot process moisture effectively in cold temperatures. It is much safer to start them indoors in a warm environment and move them outside once the ground has warmed up.

How do I know when the soil is warm enough?

The most accurate way is to use a soil thermometer and look for a reading of 60°F. If you don't have one, observe the other plants in your yard. When deciduous trees are fully leafed out and the grass is growing vigorously, the soil is usually reaching the appropriate temperature for begonias.

Should I plant begonias in the sun or shade?

Most begonias thrive in partial shade or filtered light. Morning sun is usually fine, but the intense heat of the afternoon sun can scorch their leaves and cause the flowers to fade quickly. If you have a very sunny spot, look for specific wax begonia varieties that are bred to be more sun-tolerant, but even those appreciate a little afternoon relief. If you want a broader placement guide, see Where to Plant Begonias: Sun or Shade?.