When Can I Plant Begonias Outside for Best Blooms?

Table of Contents

1. Introduction
2. Understanding Begonia Temperature Needs
3. The Best Time to Start Begonia Tubers
4. How to Tell if Your Garden is Ready
5. Moving Begonias Outside: The Hardening Off Process
6. Choosing the Right Spot for Your Begonias
7. Identifying Your Begonia Type
8. Step-by-Step Guide to Planting Outside
9. Summer Care for Maximum Color
10. Dealing with Garden Visitors
11. Planning for the End of the Season
12. Enjoying the Reward
13. FAQ

Introduction

Few sights in the garden are as rewarding as a porch lined with cascading begonias or a shaded border glowing with their vivid colors. These plants are the heavy lifters of the shade garden, offering lush foliage and constant flowers from midsummer right through the first frost. At Longfield Gardens, we love how begonia bulbs can turn a dim corner of the yard into a vibrant focal point with very little effort.

This guide is designed for home gardeners who want to know exactly when and how to move these tropical beauties outdoors. Whether you are starting with dormant tubers or young plants from a nursery, timing is the most important factor for success. For a broader overview of begonia types and care, see our All About Begonias guide. We will cover temperature requirements, how to prepare your plants for the transition, and the simple steps to keep them blooming all season long.

By understanding a few basic rules about weather and soil, you can ensure your begonias thrive from the moment they hit the garden soil. The key to success is patience, as waiting for the right outdoor conditions leads to much faster growth and more spectacular flowers.

Understanding Begonia Temperature Needs

Begonias are tropical plants by nature. They originally come from warm, humid climates in South and Central America, Africa, and Asia. Because of this heritage, they have no natural defense against cold weather. They do not just dislike frost; they also struggle when the air or soil is even slightly chilly.

The most important rule for planting begonias outside is to wait until the danger of frost has completely passed. Even a light frost can turn the juicy stems and leaves of a begonia to mush overnight. However, "frost-free" is only the first part of the equation. If you want a deeper walkthrough on timing, our Can I Plant My Begonia Outside? guide is a helpful companion.

For the best results, wait until nighttime temperatures stay consistently above 50°F. If the nights are still dipping into the 40s, your begonias will likely sit still and refuse to grow. In some cases, cold soil can even cause the tubers to rot before they have a chance to establish. If you want your plants to take off quickly, waiting until the nights are warm is the smartest move you can make.

Key Takeaway: Begonias are tropical plants that need warm air and warm soil. Do not rush them outside until the threat of frost is gone and nights are reliably 50°F or warmer.

The Best Time to Start Begonia Tubers

While begonias cannot go outside until the weather is warm, you do not have to wait until then to start the growing process. In fact, starting tuberous begonias indoors is one of the best ways to get a head start on the season. For more detail on that process, see our Tips for Growing Tuberous Begonias guide. Because begonias grow somewhat slowly at first, starting them early ensures you have large, blooming plants by the time summer arrives.

Most gardeners should start their begonia tubers indoors about 8 to 12 weeks before the average last frost date in their area. For much of the United States, this means tucking your tubers into pots in late February or March. This gives the tubers plenty of time to wake up, develop a strong root system, and push out several inches of leafy growth.

If you live in a warm climate (Zones 9-11), you may be able to plant your tubers directly into the garden once the soil has warmed. However, for everyone else, the indoor head start is the secret to a long blooming season. A begonia started indoors in March will often begin blooming in June, whereas a tuber planted outdoors in May might not show flowers until August.

Simple Steps for an Early Start

• Check your local "last frost date" using a hardiness zone map.
• Count back 10 weeks from that date to find your ideal indoor planting window.
• Gather your pots and high-quality potting mix so you are ready when the time comes.
• Place your started tubers in a warm spot with bright, indirect light.

How to Tell if Your Garden is Ready

Calendar dates are a helpful starting point, but the plants themselves care more about the actual conditions in your yard. Every year is different, and a warm April can easily be followed by a record-breaking cold May. This is why it is helpful to observe the environment rather than just following a date on a page.

Soil temperature is often a better indicator than air temperature. You can check this easily with a simple soil thermometer. Begonias prefer soil that is at least 60°F, and a quick look at the hardiness zone map can help you confirm how warm your season typically runs. If the soil is cold and clammy, the roots will not want to grow. Warm soil encourages the plant to reach out and establish itself quickly.

Another good rule of thumb is to look at other plants in your neighborhood. If you see people planting tomatoes or peppers, it is usually safe to plant begonias. These vegetable crops have very similar temperature requirements. If it is too cold for a tomato plant, it is definitely too cold for a begonia.

Moving Begonias Outside: The Hardening Off Process

Moving a begonia directly from a cozy, still indoor environment to the great outdoors can be a shock to the plant. Even if the temperatures are perfect, the outdoor world has wind, intense sunlight, and fluctuating humidity. To keep your plants healthy, you must put them through a process called "hardening off."

Hardening off is simply a gradual introduction to the outdoors. It allows the plant to toughen its cell walls and adjust to the brighter light. If you skip this step, the leaves may scorch, turn white, or drop off entirely. For a full planting walkthrough, see How Do You Plant Tuberous Begonias?. While the plant might eventually recover, it will set your blooming schedule back by several weeks.

A Typical 7-Day Hardening Off Schedule

1. Day 1-2: Place the plants in a fully shaded, sheltered spot for just 2 or 3 hours in the afternoon, then bring them back inside.
2. Day 3-4: Increase the outdoor time to 5 or 6 hours. Ensure they are still protected from strong winds and direct midday sun.
3. Day 5-6: Leave the plants out all day. If the nighttime temperatures are safely above 50°F, you can leave them out overnight in a protected spot.
4. Day 7: Your begonias are now ready to be planted in their permanent outdoor home.

Key Takeaway: Gradual exposure is the key to a smooth transition. Taking one week to transition your plants prevents leaf burn and ensures they keep growing without interruption.

Choosing the Right Spot for Your Begonias

Once the weather is right and your plants are hardened off, it is time to choose their final home. The "right plant, right place" rule is essential here. While we often think of all begonias as shade plants, their light needs can actually vary depending on the variety and your local climate.

At Longfield Gardens, we find that most tuberous begonias perform best in "dappled shade" or "filtered light." A good companion guide for that kind of planting is Summer Bulbs for Shady Gardens. This means a spot under a leafy tree or on a porch that gets morning sun but is protected from the harsh afternoon rays. If a begonia gets too much hot sun, the leaves may curl and the edges may turn brown. If it gets too much shade, it may produce plenty of leaves but very few flowers.

Soil and Drainage

Begonias have very succulent stems and roots, which means they hold a lot of water. Because of this, they are prone to rotting if they sit in soggy soil. Whether you are planting in the ground or in a container, drainage is non-negotiable.

• In Containers: Always use a pot with drainage holes. A high-quality, peat-based potting mix is usually best because it holds moisture without becoming "mucky."
• In the Ground: If your garden soil is heavy clay and stays wet after a rain, you should amend it. Mixing in some compost or finely ground bark will help create the loose, airy structure begonias love.
• Alternative: If your ground soil is very poor, consider planting begonias in raised beds or decorative urns where you can control the soil quality.

Identifying Your Begonia Type

Knowing which type of begonia you have will help you decide exactly where to plant it and what kind of care it needs. While there are thousands of varieties, most home gardeners grow one of these four common types.

Tuberous Begonias

These are the showstoppers of the family. They grow from a thick, potato-like tuber and produce massive, rose-like flowers. Tuberous begonias can be "upright," which are great for garden beds, or trailing, which are perfect for hanging baskets like Begonia Hanging Golden Balcony. They love cool, shaded spots and consistent moisture.

Wax Begonias

Wax begonias are often sold in flats as bedding plants. They have glossy, succulent leaves that are either green or bronze. These are much tougher than tuberous begonias and can often handle more sun, especially the bronze-leafed varieties. They are excellent for mass plantings or edging a walkway.

Rex Begonias

Rex begonias are grown primarily for their incredible foliage. Their leaves can feature swirls of silver, purple, pink, and deep green. While they do bloom, the flowers are small. These are very sensitive to direct sun and prefer deep shade and high humidity. Many gardeners grow them in pots so they can be moved indoors as houseplants in the winter.

Cane Begonias (Angel Wing)

These begonias grow tall, woody stems that look a bit like bamboo. The leaves are often shaped like wings and feature silver spots. Cane begonias are quite vigorous and make excellent "thriller" plants in large patio containers. They appreciate bright, indirect light and can grow several feet tall in a single season.

Step-by-Step Guide to Planting Outside

When the time is finally right to put your plants in the ground or their final pots, following a few simple steps will help them settle in quickly. Begonias are delicate, so a gentle touch goes a long way.

For Tuberous Begonias (from tubers)

If you are planting dormant tubers directly outside in a warm climate, remember that orientation matters. One side of the tuber is slightly indented or "hollow." This hollow side should always face up. For a classic upright look, Begonia Upright Double Roseform Pink is a beautiful example.

1. Dig a shallow hole: You only need to plant the tuber about 1/2 inch to 1 inch deep.
2. Place the tuber: Set it in the hole with the indented side up.
3. Cover lightly: Use loose soil to cover the tuber. Do not pack it down too hard, as the emerging sprouts are brittle.
4. Space them out: Keep tubers about 8 to 12 inches apart to allow for airflow and growth.

For Nursery Starts or Indoor-Grown Plants

1. Prepare the hole: Dig a hole that is the same depth as the current pot and twice as wide.
2. Loosen the roots: If the plant is "root-bound" (roots circling the pot), gently tease them outward with your fingers.
3. Set the depth: Ensure the top of the root ball is level with the surrounding soil. A compact, container-friendly choice like Begonia Upright Double Picotee White settles in especially well.
4. Water in: Give the plant a gentle drink of water immediately after planting. This helps settle the soil around the roots and removes air pockets.

Summer Care for Maximum Color

Once your begonias are settled in their outdoor home, a little bit of routine care will keep them looking like a professional display. Because begonias are such heavy bloomers, they appreciate consistent attention to water and food.

Watering Rules

Begonias prefer to stay "evenly moist." This means the soil should feel like a wrung-out sponge—not soaking wet, but not bone dry.

• Check the soil daily, especially for plants in hanging baskets or small pots.
• Stick your finger an inch into the soil. If it feels dry, it is time to water.
• Always water the soil, not the leaves. Getting the foliage wet can encourage mildew or fungal issues.
• Early morning is the best time to water so any accidental splashes can dry in the sun.

Feeding Your Plants

Because begonias bloom continuously from July until the first frost, they use up a lot of energy. Regular fertilizing is the best way to keep the flower production high.

• Use a balanced, water-soluble fertilizer every two to three weeks.
• Alternatively, you can mix a slow-release granular fertilizer into the soil at planting time.
• Look for a fertilizer with a slightly higher "middle number" (phosphorus) to encourage more blooms.

Deadheading and Grooming

Many modern begonias, like the Surefire or Double Delight series, are "self-cleaning." If you prefer a big, easy-care planting, Non Stop Begonias are another dependable choice. This means the old flowers fall off on their own, so you do not have to spend hours "deadheading" or pinching off dead blooms. However, it is still a good idea to pick up those fallen petals if they land on the leaves, as they can sometimes cause spots in humid weather.

If your plants start to look "leggy" or stretched out in mid-August, don't be afraid to pinch back the tips of the stems. This encourages the plant to branch out and become bushier, leading to even more flowers in the fall.

Dealing with Garden Visitors

Gardening is a shared experience with nature, and occasionally, local wildlife or insects might take an interest in your begonias. The good news is that begonias are generally not the first choice for many common pests.

Wildlife

Deer and rabbits usually find begonias less tasty than hostas or lilies. However, if they are hungry enough, they may take a nibble. If you have high wildlife pressure, planting begonias in elevated containers or on a porch is usually enough to keep them safe.

Insects and Issues

The most common issue with begonias is not bugs, but fungus. Powdery mildew can appear as a white, flour-like dusting on the leaves if the air is stagnant and the leaves stay wet.

• The fix: Ensure your plants have good airflow and always water at the base of the plant.
• Small Pests: Occasionally, you might see aphids or mealybugs. These can usually be handled with a gentle spray of insecticidal soap or simply by wiping them off with a damp cloth.

Key Takeaway: Prevention is the best medicine. Providing the right amount of light, good drainage, and airflow will prevent almost all common begonia problems before they start.

Planning for the End of the Season

As summer winds down and the first hints of autumn arrive, you have a choice to make. Most begonias are treated as annuals in the United States, meaning they are enjoyed for one season and then replaced. However, because they grow from tubers or can live as houseplants, you can actually save them for next year.

Saving Tuberous Begonias

When the leaves start to turn yellow in the fall, or after the first very light frost blacks the foliage, it is time to dig them up.

1. Lift the tubers: Carefully dig up the tubers and cut off the stems, leaving about an inch of stalk.
2. Dry them out: Let the tubers sit in a cool, dry place for a few days until the remaining stem dries up and falls off naturally.
3. Store for winter: Place the clean tubers in a box of peat moss or sawdust. Keep them in a cool (around 50°F), dark place like a basement or crawlspace.
4. Wait for spring: Check them occasionally to make sure they aren't shriveling or rotting. In March, you can bring them back into the light and start the cycle all over again!

Saving Rex or Wax Begonias

These varieties do not have tubers to store, but they make excellent indoor plants. Before the temperatures drop below 50°F, pot them up and bring them inside. Place them in a bright window and reduce your watering. They may drop a few leaves as they adjust to the lower humidity of your home, but they will often bounce back and provide beautiful foliage all winter.

Enjoying the Reward

The beauty of begonias is that they offer a massive reward for a relatively small amount of work. Once you get the timing of the outdoor transition right, the rest of the season is largely about enjoying the show. Whether you use them to brighten a dark porch or to add texture to a shaded garden bed, begonias provide a level of color that few other shade-loving plants can match.

At Longfield Gardens, we believe that gardening should be a source of joy, not stress. By waiting for those warm nights and giving your plants a week to get used to the outdoors, you are setting yourself up for a summer filled with stunning blooms.

• Wait for 50°F nights before planting outside.
• Start tubers indoors 10 weeks early for a head start.
• Harden off plants for one week to avoid leaf scorch.
• Prioritize well-drained soil and dappled shade.

"The secret to a spectacular begonia display isn't a green thumb—it's a patient heart. Wait for the warmth, and the plants will do the rest."

We invite you to explore the many colors and forms of begonias available. With a little bit of planning, your garden can become a shaded paradise that blooms from the heat of July through the crisp days of October.

FAQ

What happens if I plant my begonias outside too early?

If you plant begonias before the soil and air have warmed up, the plants will likely stop growing. In the worst-case scenario, a late spring frost will kill the foliage and stems instantly. Even if it doesn't freeze, cold and wet soil can cause the tuber or roots to rot, leading to the loss of the plant. It is always better to wait an extra week for warm weather than to rush and risk the health of your flowers.

Do I need to dig up my begonias every year?

In USDA hardiness zones 9 through 11, begonias can often stay in the ground year-round. However, for most of the United States (zones 3 through 8), begonias will not survive the winter outside. You can either treat them as annuals and buy new ones each spring, or you can dig up the tubers in the fall and store them in a cool, dry place to replant the following year.

Can begonias grow in full sun?

Most begonias prefer partial shade or filtered light, but some varieties are more sun-tolerant than others. Wax begonias with bronze-colored leaves are known for their ability to handle more direct sunlight. However, in very hot climates, even sun-tolerant begonias usually appreciate some protection from the intense afternoon sun to prevent their leaves from scorching or wilting.

Why are the leaves on my begonia turning yellow and falling off?

Yellowing leaves are usually a sign of one of two things: overwatering or a lack of nutrients. First, check the soil moisture; if it feels soggy or smells sour, the plant may be getting too much water. Ensure your pot or garden bed has excellent drainage. If the drainage is good, your plant might just be hungry. Try applying a balanced, water-soluble fertilizer to give it the energy it needs to produce new, green growth.