When Should You Plant Begonias? The Timing Guide

Table of Contents

1. Introduction
2. Understanding the Begonia Planting Window
3. The Strategy: Indoor Starting vs. Outdoor Planting
4. How Temperature Dictates Your Schedule
5. Regional Timing and USDA Zones
6. The Impact of Variety on Planting Time
7. Step-by-Step: Starting Tubers Indoors
8. Transitioning to the Garden: The Hardening Off Process
9. Realistic Expectations for Growth and Bloom
10. Adjusting for Containers vs. In-Ground Beds
11. Common Timing Myths
12. Planning for the End of the Season
13. Summary of Success
14. FAQ

Introduction

There is nothing quite like the sight of a shaded porch or a quiet garden corner erupting into a sea of brilliant begonias. These versatile plants are a favorite for a reason, offering lush foliage and rose-like blooms that can brighten up even the dimmest spots in your landscape. At Longfield Gardens, we know that the secret to a spectacular summer display starts with one critical factor: timing.

This guide is designed to help you understand exactly when to plant your begonias, whether you are starting them from tubers indoors or transplanting them into your garden beds. We will cover the specific temperature requirements, how to use your local frost dates, and why patience is your best friend when it comes to these tropical beauties. By the end of this article, you will have a clear timeline for a successful growing season.

The key to begonia success is simple: these plants love warmth and hate the cold, so matching your planting schedule to the local weather is the most important step you can take.

Understanding the Begonia Planting Window

Begonias are tropical plants by nature. They are native to warm, humid regions of Central and South America, Asia, and Africa. Because of their heritage, they have no natural defense against frost or cold soil. If you plant them too early, the tubers can rot in cold, damp ground, or the tender foliage can be damaged by a late spring chill.

The ideal window for planting begonias outdoors begins only when the danger of frost has completely passed. For most gardeners in the United States, this happens sometime between late April and early June. However, because the country spans so many different climate zones, the exact date depends entirely on your local conditions and the USDA hardiness zone map.

A good rule is to wait until nighttime temperatures are consistently staying above 50°F. If the nights are still dipping into the 40s, it is better to keep your plants protected. Begonias thrive when the soil is warm, specifically around 60°F or higher. When the soil is warm, the roots can grow quickly and the plant can begin producing the energy it needs for those famous summer flowers.

The Strategy: Indoor Starting vs. Outdoor Planting

One of the most common questions we hear is whether you should start begonias indoors or wait to put them directly in the ground. The answer depends on how long you want your blooming season to be.

Starting Begonia Tubers Indoors

Because begonias can take a while to wake up and reach their full blooming potential, many gardeners choose to start them indoors. Our How to Start Tuberous Begonias Indoors guide walks through the process.

We recommend starting your tuberous begonias indoors about 8 to 12 weeks before the average last frost date in your area. If you live in a northern climate with a short summer, this is an excellent way to ensure you get several months of flowers. By starting them in March or April, you can often have plants that are ready to bloom by the time Memorial Day arrives.

Planting Directly Outdoors

If you live in a warmer climate with a long growing season, you might choose to plant your tubers directly into the garden. In this case, you must wait until the soil is warm and the weather is settled. This usually means waiting until late May or early June in many parts of the country. While this is the easiest method, keep in mind that your begonias may not start blooming until mid-to-late summer because they have to do all their growing from scratch in the ground.

Key Takeaway: Start your tubers indoors 8-12 weeks before the last frost for the longest possible bloom season. If you prefer to plant directly outdoors, wait until the soil is at least 60°F.

What to Do Next: Early Spring Planning

• Look up the average last frost date for your specific zip code.
• Count back 10 weeks from that date on your calendar.
• Mark that day as your "Start Indoors" date for begonia tubers.
• Check your garden containers to ensure they are clean and have proper drainage holes.

How Temperature Dictates Your Schedule

Temperature is more than just a number on a thermometer; it is the biological "green light" for begonias. Understanding the difference between air temperature and soil temperature will help you time your planting perfectly.

Air Temperature Requirements

Begonias are very sensitive to "cold snaps." Even if it isn't freezing, a night where the temperature drops to 40°F can stun the plants, causing them to stop growing for a week or more. For the best results, wait until the forecast shows a steady trend of nighttime temperatures above 50°F. If you have already moved your plants outside and a surprise cold night is forecasted, it is worth the effort to move pots into a garage or cover garden beds with a light frost cloth.

Soil Temperature Requirements

The soil takes much longer to warm up than the air. In the spring, the air might feel like 70°F, but the ground could still be a chilly 45°F. Tuberous begonias are particularly susceptible to rot if they sit in cold, wet soil.

If you are planting in the ground, wait until the soil feels warm to the touch. If you are planting in containers or hanging baskets, you have a bit more flexibility. Container soil warms up much faster than the ground because it is surrounded by warm air. This is why many gardeners find that their potted begonias take off much faster in the spring than those planted in garden borders, especially Begonia Hanging Pink Balcony.

Regional Timing and USDA Zones

At Longfield Gardens, our shipping schedule is based on your USDA hardiness zone to help you get the timing right. We aim to have your order arrive about two weeks before the ideal planting time for your area.

Zones 3 to 7 (Northern and Central US)

In these cooler zones, the growing season is relatively short. Starting begonias indoors is highly recommended. You will likely be starting your tubers inside between February and April and moving them outdoors in late May or early June. In these regions, begonias are treated as annuals, meaning they will not survive the winter outside and must be dug up and stored if you wish to keep them for next year.

Zones 8 to 9 (Southern and Coastal US)

In these regions, you have a much wider window. You can often start begonias outdoors in April. However, you should be mindful of the heat. While begonias love warmth, intense afternoon sun in the South can be too much for them. Timing your planting for early spring helps the plants establish themselves before the peak heat of July and August.

Zones 10 to 11 (Tropical US)

In the warmest parts of the country, begonias can often be grown as perennials. You can plant them almost any time the weather is not excessively hot and dry. In these zones, the focus shifts from protecting them from the cold to ensuring they have enough shade and water to stay cool.

The Impact of Variety on Planting Time

While most begonias follow similar rules, there are slight differences depending on the types of begonias you are growing.

Tuberous Begonias

These are the most common type for gardeners looking for large, showy blooms, and Non Stop Begonias are a classic example. Because they grow from a thick tuber, they have a "dormancy" period. They need to be "woken up" in the spring with moisture and warmth. This process takes time, which is why they benefit the most from an early start indoors.

Wax Begonias (Fibrous-Rooted)

These are often sold as small "plugs" or started plants in six-packs at nurseries. Since they are already growing when you buy them, you don't need to start them weeks in advance. However, you still must wait for the same warm weather. Do not be tempted by the early displays at garden centers in March; wait until the weather is truly warm before putting these bedding plants in the ground.

Rex Begonias

Grown primarily for their stunning, colorful foliage, Rex begonias are often kept as houseplants. If you plan to move them to a shaded patio for the summer, the timing is the same: wait for those 60°F nights. They are even more sensitive to humidity and temperature fluctuations than flowering varieties.

Hardy Begonias (Begonia grandis)

This is the rare exception to the "annual" rule. Hardy begonias can survive the winter in zones 6 through 9. They are late to emerge in the spring, often not showing signs of life until May or June. If you have these in your garden, don't worry if you don't see them early in the season—they are just waiting for the soil to reach their preferred temperature.

Step-by-Step: Starting Tubers Indoors

If you decide to give your begonias a head start, following a simple process will ensure they wake up healthy and ready to grow.

1. Check the Tubers: When your order arrives, open the package immediately. The tubers should feel firm, like a healthy potato. If you aren't ready to plant them yet, store them in a cool, dry, dark place.
2. Choose the Right Container: Use shallow trays or small pots with excellent drainage. A high-quality, peat-based potting mix is ideal because it holds moisture without becoming waterlogged.
3. Find the "Up" Side: Begonia tubers have a concave side (it looks like a little bowl or a thumbprint) and a rounded side. The concave side is the top. This is where the sprouts will emerge.
4. Planting Depth: Place the tuber into the soil with the hollow side facing up. Cover it with only about half an inch to an inch of soil. You want the tuber to be tucked in, but not buried so deep that the sprouts struggle to reach the light. For more detail, see our Tips for Growing Tuberous Begonias.
5. Water Sparingly: This is the most important part of early timing. Water the soil once to settle it, then wait. Do not water again until you see green sprouts poking through the soil. Overwatering a dormant tuber is the fastest way to cause rot.
6. Provide Warmth and Light: Place the containers in a warm spot (around 70°F). They don't need light until the sprouts appear, but once you see green, move them to a bright window or under a grow light.

Key Takeaway: The "hollow" side of the tuber faces up. Only water once at planting and then wait for the sprouts to appear to avoid rot.

Transitioning to the Garden: The Hardening Off Process

Timing your move to the garden is a two-step process. You cannot simply take a plant from a 70°F living room and put it directly into the garden. It needs to be acclimated to the outdoor environment—a process called "hardening off." For more on shade, timing, and outdoor placement, see Summer Bulbs for Shady Gardens.

Once the outdoor temperatures are appropriate, start by placing your begonias in a sheltered, shady spot outside for just two or three hours a day. Gradually increase their time outside over the course of a week. This allows the leaves to toughen up and get used to the wind and the shift in light intensity.

If the weather forecast shows a sudden dip in temperature during this week, keep the plants inside for an extra day. There is no rush; the goal is a healthy plant, not a fast one.

What to Do Next: The Transition Week

• Monitor the 10-day weather forecast for any late-season frost warnings.
• Find a protected spot on a porch or under a tree for the first day of hardening off.
• Prepare your outdoor pots or garden soil by mixing in a little compost.
• Ensure your outdoor location has the right amount of shade (morning sun is usually best).

Realistic Expectations for Growth and Bloom

When you plant begonias, it is helpful to know what the timeline for growth actually looks like. Gardening is a rewarding exercise in patience, and begonias follow their own internal clock.

In the first few weeks after planting (whether indoors or out), you might not see much happening above the soil. This is normal. The tuber is busy growing a network of fine white roots. Once the root system is established, you will see a burst of foliage growth.

Typically, it takes about 12 to 14 weeks from the time you plant a tuber to the time you see the first flowers. If you start your tubers in mid-March, you can expect flowers by late June or early July. If you wait to plant tubers outdoors in June, you might not see blooms until August. This is why the "when" of planting is so closely tied to how much enjoyment you get out of the garden.

Weather will also play a role. In a particularly cool, cloudy summer, begonias may grow more slowly. In a warm, humid summer, they will thrive and may require more frequent watering.

Adjusting for Containers vs. In-Ground Beds

The timing of your planting can also be influenced by where you are putting your begonias.

Hanging Baskets and Pots

As mentioned earlier, containers warm up quickly. This means you can often move your containers outside a week or two earlier than you would plant in the ground, provided you are willing to bring them inside if a cold night is predicted. Hanging Begonias are especially well suited to this early-container approach.

Garden Beds and Borders

If you are planting Upright Double Begonias in the ground, you must be more cautious. Ground soil retains the winter chill much longer. If you have a spot that is heavily shaded by a building or thick evergreen trees, that soil will be even colder. Using a simple soil thermometer can take the guesswork out of the process. When the ground consistently measures 60°F at a depth of three inches, it is safe to plant.

Common Timing Myths

In the world of gardening, there are many "rules of thumb" that can sometimes lead beginners astray. Let's clarify a few things regarding begonia timing.

Myth: You should plant as soon as the local garden center has them in stock. Retailers often stock plants based on the calendar rather than the specific weather of the year. Just because begonias are for sale doesn't mean it's the right time to put them in the ground. Use your local weather forecast as your ultimate guide.

Myth: Planting them deeper protects them from a late frost. Planting tubers too deep won't protect them from freezing; it will only make it harder for the sprouts to emerge and increase the chance of the tuber rotting. Stick to the recommended depth of about one inch.

Myth: If I plant them in April, they will definitely bloom in May. Begonias have a set biological timeline. They need roughly three months to go from a dormant tuber to a flowering plant. You cannot rush this process with extra fertilizer or water. Starting early is the only way to get early blooms.

Planning for the End of the Season

While this guide focuses on the beginning of the season, the "when" of planting is bookended by the "when" of the first frost in autumn.

As the summer winds down and the first hints of autumn arrive, pay attention to the temperatures again. Begonias will continue to bloom right up until the first frost. Once the foliage has been touched by frost, it will turn black and limp. This is the signal that the growing season is over.

If you live in a cold zone and want to save your tubers for next year, you should dig them up shortly after that first light frost. If you wait too long and the ground freezes, the tubers will be destroyed. Timing the end of the season is just as important as timing the beginning if you want to enjoy your begonias year after year.

Summary of Success

Getting the timing right for your begonias is the most effective way to ensure a beautiful, stress-free garden. By respecting their tropical nature and waiting for the warmth they crave, you set the stage for a spectacular display.

Remember that while starting indoors requires a bit more effort, the reward is a significantly longer season of color. Whether you are a seasoned gardener or a beginner, the joy of watching those first sprouts emerge never fades.

At Longfield Gardens, our Begonia Non Stop Mix tubers are selected for their quality and size, giving you the best possible start. With a little bit of planning and the right weather, your garden will soon be the neighborhood's favorite shaded retreat.

Final Thought: Patience in the spring leads to brilliance in the summer. Wait for the warmth, and your begonias will reward you with nonstop color until the first frost of autumn.

• Start tubers indoors 8-12 weeks before your last frost for early blooms.
• Wait for nighttime temperatures to stay above 50°F before moving plants outside.
• Ensure the soil is at least 60°F for in-ground planting.
• Use the "hollow side up" rule when planting tubers.
• Acclimate your plants to the outdoors slowly through the hardening off process.

FAQ

Can I plant begonias in March?

In most parts of the United States, March is too early to plant begonias outdoors because of the risk of frost and cold soil. However, March is the perfect time to start begonia tubers indoors in pots. By starting them inside now, you give them a head start so they are ready to bloom as soon as the summer heat arrives. For more spring-planted timing advice, see our FAQs - Spring Planted Bulbs.

What happens if I plant my begonias too early?

If begonias are planted while the soil is still cold and damp, the tubers are highly likely to rot before they ever sprout. If the plants have already grown leaves and are hit by a late frost, the foliage will blacken and die. It is always better to wait an extra week for warm weather than to risk losing your plants to a spring cold snap.

Do begonias need a certain soil temperature?

Yes, begonias prefer soil temperatures to be at least 60°F. If the soil is colder than this, the plant's growth will remain stagnant, and the roots may struggle to establish. In northern climates, the soil usually reaches this temperature about two to three weeks after the last frost date.

How do I know when the last frost date is in my area?

The best way to find your last frost date is to check with a local university extension service or use an online frost date calculator by entering your zip code. Keep in mind that these dates are averages; it is always a good idea to watch your local seven-day forecast for any unexpected dips in temperature before planting.