Table of Contents
- Introduction
- When to Plant Begonia Tubers
- Right Plant, Right Place: Choosing a Location
- How to Plant Begonia Tubers Step-by-Step
- Starting Indoors: The Sprouting Phase
- Moving Begonias Outdoors (Hardening Off)
- Caring for Your Begonias All Summer
- Different Types of Begonias to Try
- Realistic Expectations for Your Garden
- Overwintering: Saving Your Tubers
- FAQ
- Conclusion
Introduction
Tuberous begonias are the secret to a spectacular shade garden. While many flowering plants require full sun to produce a showy display, begonias thrive in those quiet, cool corners of the yard. They offer lush foliage and massive, rose-like blooms that continue from midsummer all the way until the first frost. Whether you want to brighten up a covered porch with hanging baskets or add a splash of color to a woodland border, these plants are a perfect choice.
At Longfield Gardens, we want to help you feel confident in your garden. Tuberous begonias are rewarding because they are easy to handle and offer a long season of beauty. They come in an incredible array of colors, from soft pastels to bold, fiery oranges and reds. Because they grow from tubers, they have a built-in energy reserve that helps them get off to a strong start once the weather warms up.
This guide will walk you through everything you need to know about starting your begonias. We will cover the best timing for your climate, how to tell which side of the tuber is up, and simple tips for ongoing care. By following a few basic steps, you can enjoy a professional-looking floral display with very little stress.
When to Plant Begonia Tubers
Timing is everything when it comes to begonias. These are tropical plants that love warmth and humidity. They are very sensitive to cold temperatures and frost. To get the most out of your growing season, you have two main options: starting them indoors or planting them directly outside.
Starting Begonia Tubers Indoors
Most gardeners in the United States prefer to start their begonia tubers indoors. This gives the plants a "head start" while the weather is still chilly outside. Because begonias can take several weeks to sprout and even longer to reach blooming size, starting early ensures you get flowers by early summer.
The best time to start begonia tubers indoors is about 8 to 12 weeks before the average last frost date in your area. For many regions, this means planting in late February, March, or early April. Starting them at this time allows the tuber to wake up and develop a strong root system and a few leaves before it ever touches outdoor soil.
Planting Begonia Tubers Outdoors
If you prefer to wait and plant directly in the garden or in outdoor containers, patience is key. You must wait until all danger of frost has passed. More importantly, the soil needs to be warm. A good rule of thumb is to wait until nighttime temperatures stay consistently above 50°F to 60°F.
If you plant a begonia tuber in cold, wet soil too early, it will sit dormant and may struggle to grow. Waiting for the right temperature is a simple way to ensure success. In many northern states, this window usually opens in late May or early June.
Shipping and Hardiness Zones
We coordinate our shipping schedule at Longfield Gardens based on your USDA hardiness zone. This means your tubers will typically arrive about two weeks before the ideal planting time for your specific region. When your package arrives, it is a great signal that it is time to get your pots and soil ready.
What to do next:
- Check your local "last frost date" online or through a local extension office.
- Count back 8 weeks from that date to find your ideal indoor starting window.
- Gather your pots and potting mix so you are ready to go as soon as your tubers arrive.
Right Plant, Right Place: Choosing a Location
Before you dig your first hole, it is important to find the right home for your begonias. Matching the plant’s needs to your garden’s conditions is the easiest way to ensure a healthy, blooming plant.
Light Requirements
Tuberous begonias are famous for their love of shade gardens, but they do need some light to produce those big, beautiful flowers. The best spot is one with "filtered" or "dappled" sunlight. This is the kind of light you find under a high-canopy tree or on a porch that gets soft morning sun.
Try to avoid spots that receive harsh, direct afternoon sun. The intense heat of the mid-afternoon can scorch the leaves and cause the flowers to wilt. If you live in a very hot climate, your begonias will appreciate even more shade. If you live in a cooler, northern climate, they can often handle a bit more morning sun.
Soil and Drainage
"Drainage" is a word gardeners use to describe how quickly water moves through the soil. Begonias love moisture, but they hate sitting in "wet feet" (soggy soil). If the soil stays too wet for too long, the tuber can rot.
If you are planting in begonias in a pot, always use a high-quality potting mix and make sure the pot has drainage holes at the bottom.
Protection from Wind
Begonias have thick, succulent stems that can be somewhat brittle. If you place them in a very windy spot, a strong gust could snap a stem or knock over a tall plant. Choose a location that is somewhat sheltered, such as near a fence, under a porch roof, or tucked among other sturdy plants.
How to Plant Begonia Tubers Step-by-Step
Once you have your tubers and your location picked out, it is time to plant. Begonia tubers look like small, brown, fuzzy discs or bowls. They might look a little strange at first, but they are full of potential.
Step 1: Identify the "Up" Side
This is the most common question gardeners ask about which side is up. Begonia tubers have a distinct shape. One side is usually rounded, and the other side has a hollow or indented "bowl" shape.
The hollow, indented side should face up. This is where the stems and leaves will emerge. The rounded side should face down into the soil. If you look closely at the hollow side, you might see small, pinkish buds or "eyes." These are the beginnings of your new stems.
Step 2: Prepare Your Growing Medium
If you are starting indoors, use a shallow tray or small individual pots. Fill them with a lightweight potting mix or a blend of peat moss and perlite. Moisten the mix slightly before you plant. It should feel like a wrung-out sponge—damp but not dripping wet.
Step 3: Planting Depth
Begonias do not like to be buried deep. In fact, they prefer to be just barely covered. Place the tuber in the soil with the hollow side up. Press it down gently so it is nestled into the mix.
You only need about 1/2 inch to 1 inch of soil over the top of the tuber. If you are starting them in trays indoors, some gardeners even leave the very top of the tuber exposed until they see sprouts. For outdoor planting, a light covering of soil helps protect the tuber from drying out.
Step 4: Spacing
Give your begonias room to breathe. Proper spacing ensures good air circulation, which helps prevent leaf issues later in the summer.
- In Garden Beds: Space tubers 8 to 12 inches apart.
- In Containers: You can plant them a bit closer for a full look. A single tuber fits well in a 6-inch pot. A 12-inch container can usually hold three tubers.
Step 5: Initial Watering
After planting, give the soil a light watering to help it settle around the tuber. Be careful not to pour water directly into the "hollow" of the tuber, as standing water there can lead to rot before the plant even starts growing. Instead, water the soil around the edges.
Key Takeaway: Plant your begonia tubers with the hollow side facing up and cover them with only about half an inch of soil. This shallow planting allows the stems to emerge easily and prevents the tuber from staying too wet.
Starting Indoors: The Sprouting Phase
If you choose to start your begonias inside, you will get to watch the exciting "waking up" process. This stage requires a little bit of patience, but it is very simple.
Light and Temperature
Place your pots or trays in a warm spot with indirect light. A temperature of about 70°F is ideal for encouraging sprouts. You do not need bright grow lights at this stage. A warm room with a window is usually enough to get them moving.
Moisture Control
During the first few weeks, the tubers are very sensitive. The most important rule is: do not overwater. Because there are no leaves yet, the plant isn't "drinking" much water. The soil only needs to stay slightly damp. Check the soil with your finger. If it feels moist, leave it alone. If the top inch feels dry, add a small amount of water.
What to Expect
It can take 2 to 4 weeks for the first sprouts to appear. Sometimes it takes even longer if the room is cool. Don't worry if they seem slow at first. Once the first pink buds turn into green leaves, the growth will speed up significantly.
Once the stems are about an inch tall, you can move the plants to a brighter spot. This helps the stems stay short and sturdy rather than becoming tall and "leggy."
Moving Begonias Outdoors (Hardening Off)
If you started your begonias indoors, you cannot move them directly into the garden the moment it gets warm. They need a transition period called hardening off. This allows the tender leaves to get used to the wind, varying temperatures, and brighter light of the outdoors.
The Two-Week Process
About two weeks before you plan to plant them permanently outside, start taking them out for "field trips."
- Days 1-3: Place the pots in a fully shaded, protected spot outside for 2 to 3 hours during the warmest part of the day. Bring them back inside at night.
- Days 4-7: Increase the time outside by an hour or two each day. Allow them to experience a little bit of dappled light.
- Days 8-14: Gradually move them to their final location. If the nighttime temperatures are safely above 60°F, you can start leaving them out overnight.
By the end of two weeks, your begonias will be tough enough to handle the outdoor environment and will continue growing without a hitch.
Caring for Your Begonias All Summer
Once your begonias are settled in their permanent homes, they are relatively low-maintenance. Getting the basics right—water and food—will result in a lush, flower-filled season.
Watering Correctly
The best way to water begonias is "deeply and then dry." This means you should water until it runs out of the bottom of the pot (or soaks deep into the garden bed), and then wait for the top inch of soil to feel dry before watering again.
Avoid watering the leaves and flowers if possible. Watering at the base of the plant keeps the foliage dry, which helps prevent mildew. During the hottest parts of the summer, check your containers daily. Hanging baskets, in particular, dry out much faster than garden beds.
Feeding for Better Blooms
Begonias are "heavy feeders." This means they use a lot of energy to produce those massive flowers and need extra nutrients.
Start fertilizing once the plant has several sets of leaves. A balanced, water-soluble fertilizer works best. You can use it at half-strength every two weeks, or follow the instructions on the product label. Consistent feeding ensures the plant has the fuel it needs to keep blooming until autumn.
Deadheading and Grooming
"Deadheading" is the practice of removing faded or spent flowers. For begonias, this isn't always strictly necessary for the plant to keep blooming, but it keeps the display looking tidy.
If you see a flower that is turning brown or wilting, simply pinch it off at the stem. You should also remove any yellowing or damaged leaves. This simple grooming helps with air circulation and keeps the plant focused on new growth.
Staking Tall Varieties
Some upright begonias produce flowers so large and heavy that the stems might lean or sag. If you notice your plant looks a bit top-heavy, you can use a small bamboo stake and some soft garden twine to give it support. Be gentle when tying the stems, as they are succulent and can be bruised easily.
Summer Care Action List:
- Water the soil, not the leaves, when the top inch is dry.
- Apply a balanced liquid fertilizer every two weeks.
- Pinch off faded blooms to keep the plant looking fresh.
- Check hanging baskets daily during heatwaves.
Different Types of Begonias to Try
When you browse our selection at Longfield Gardens, you will notice that begonias come in several different styles. Choosing the right "habit" (the way the plant grows) will help you achieve your design goals.
Upright Begonias
These varieties grow vertically and are perfect for garden borders or large patio pots. Varieties like Roseform Pink produce huge, multi-petaled blooms that look exactly like roses. "Fimbriata" varieties have ruffled, fringed edges that add a unique texture to the garden. These are the showstoppers of the begonia world.
Trailing (Pendula) Begonias
If you have hanging baskets or window boxes, trailing begonias are a must. Instead of growing up, these varieties cascade over the sides of the container. They produce a high volume of slightly smaller flowers, creating a "waterfall" effect of color. They are perfect for eye-level displays where you can appreciate the hanging blooms.
Specialty Shapes
There are also "Bouton de Rose" types which have a distinct rosebud center, and bicolor varieties that feature petals with contrasting edges. Mixing and matching these different shapes and habits is a great way to add visual interest to a shady porch.
Realistic Expectations for Your Garden
Gardening is a partnership with nature, and results can vary based on your local conditions. It is helpful to keep a few things in mind:
- Growth Rate: Begonias can be slow to start. If your neighbor’s petunias are already blooming and your begonias are just starting to show leaves, don't worry! Begonias are "marathon runners," not sprinters. They take a while to get going, but they finish the season stronger than almost any other flower.
- Weather Impact: Extreme heat (above 90°F) can cause begonias to take a short "break" from blooming. They are conserving energy. Once the temperatures dip back into a comfortable range, they will resume their flower production.
- Bloom Size: The very first flowers of the season might be a bit smaller than the ones that appear in August. As the plant's root system grows larger, the flowers will become more impressive.
Overwintering: Saving Your Tubers
One of the best things about tuberous begonias is that you can overwinter your tubers from year to year. In most parts of the US, they are treated as annuals, but with a little effort, you can store the tubers and replant them next spring.
Preparing for Dormancy
In the fall, as the days get shorter and temperatures drop, your begonias will naturally start to slow down. The leaves may begin to turn yellow. This is a sign that the plant is moving its energy down into the tuber for winter storage.
After the first light frost kills the top of the foliage (or just before a hard freeze), it is time to dig them up.
- Lift the Tubers: Carefully dig up the tubers, being sure not to nick them with your shovel.
- Dry and Cure: Cut the stems back to about an inch long. Let the tubers sit in a dry, protected spot (like a garage or basement) for a few days until the remaining stem piece dries up and falls off naturally.
- Store: Place the clean, dry tubers in a box filled with peat moss, sawdust, or even just tucked into paper bags.
- The Ideal Environment: Keep them in a cool, dark, and dry place that stays around 40°F to 50°F. A basement or an unheated (but frost-free) closet is perfect.
Next spring, you can pull them out, check for any soft spots, and start the whole process over again!
FAQ
Which side of the begonia tuber should face up when planting?
The hollow or indented side of the tuber should always face up. This concave area is where the growing points (eyes) are located. The rounded, smoother side should face down into the soil to allow the roots to grow.
Do I need to soak begonia tubers before planting?
You do not need to soak them. While some gardeners find it helps "wake them up," begonias are prone to rot if they get too wet too fast. It is generally safer to plant them in slightly damp potting mix and let them absorb moisture naturally from the soil.
Why are my begonia tubers not sprouting?
The most common reasons are cold temperatures or overwatering. Begonias need warmth (around 70°F) to sprout. If your room is cool, they may stay dormant for several weeks. Ensure the soil is damp but never soggy, as too much water can cause the tuber to rot before it can grow.
Can begonias grow in full sun?
Tuberous begonias generally prefer partial shade to full shade. While they can handle some gentle morning sun, direct afternoon sun in most climates is too intense and will likely scorch the leaves and cause the flowers to drop prematurely.
Conclusion
Tuberous begonias are truly one of the most rewarding plants for any home gardener. By understanding the simple rules of when and how to plant them, you can transform a shady corner into a vibrant oasis. Remember to look for the hollow side of the tuber, keep the soil moist but not wet, and give them a little extra food during the summer months.
At Longfield Gardens, our 100% Quality Guarantee means we take pride in providing high-quality tubers that are true to variety and ready to perform in your yard. Whether you are a beginner or a seasoned pro, the joy of seeing those first rose-like blossoms emerge is a highlight of the gardening season.
Final Takeaway: For the best results, start your begonias indoors 8 weeks before the last frost. Place them in a warm spot, plant them shallowly with the hollow side up, and wait for the soil to warm before moving them outside.
If you are ready to add some color to your shade, visit us at Longfield Gardens to shop by color and start planning your most beautiful summer garden yet.