How to Grow Begonias From Seed

Table of Contents

1. Introduction
2. The Benefits of Growing Begonias From Seed
3. Understanding Begonia Seeds
4. When to Start Your Begonia Seeds
5. Essential Supplies for Success
6. Preparing the Growing Medium
7. How to Sow Begonia Seeds Step-by-Step
8. Providing the Right Environment for Germination
9. Caring for Begonia Seedlings
10. Transplanting Into Larger Pots
11. Pinching and Shaping Your Plants
12. Hardening Off and Moving Outdoors
13. Choosing the Best Spot in Your Garden
14. Caring for Your Mature Begonias
15. Storing and Saving Your Own Seeds
16. Conclusion
17. FAQ

Introduction

Growing begonias from seed is one of the most rewarding projects a gardener can take on during the quiet winter months. There is something truly magical about watching a speck of seed—no larger than a grain of dust—transform into a lush, flowering plant that will brighten your garden all summer. While many people choose to start with tubers or nursery-grown starts, starting from seed opens up a world of unique varieties and colors that you won't find anywhere else.

At Longfield Gardens, we love helping gardeners discover the joy of growing beautiful flowers from the ground up. This guide is designed for anyone who wants to try their hand at raising these stunning plants indoors before the spring arrives. We will cover everything from the supplies you need to the exact steps for sowing, transplanting, and eventually moving your healthy begonias out into the sunshine.

Whether you are a seasoned gardener or a beginner looking for a fun indoor project, you will find that a little patience goes a long way with begonias. By following a few simple steps, you can fill your patio containers, hanging baskets, and garden beds with vibrant blooms. Success with begonia seeds is all about timing, light, and consistent care.

The Benefits of Growing Begonias From Seed

One of the best reasons to grow begonias from seed is the sheer variety available. Most garden centers carry only the most popular wax or tuberous types, but the world of begonia seeds is much broader. You can find unique leaf patterns, rare flower colors, and different growth habits that make your garden stand out. If you have a specific color theme in mind for your summer containers, growing from seed is often the most reliable way to get exactly what you want.

Cost is another significant advantage. A single packet of seeds often contains dozens, if not hundreds, of potential plants for a fraction of the cost of buying individual starts. This is especially helpful if you have a large landscape to fill or if you enjoy creating several hanging baskets to line a porch. Starting your own plants allows you to grow in bulk without stretching your gardening budget. If you want more ready-to-plant options, see our Begonia Non Stop Mix for another easy way to fill shady spaces with color.

Finally, there is a deep sense of satisfaction in the process. Starting seeds in January or February gives you a reason to get your hands in the soil while the ground outside is still frozen. Watching those tiny green sprouts emerge is a great way to beat the winter blues and get a head start on the growing season.

Understanding Begonia Seeds

Begonia seeds are remarkably small. In fact, they are among the smallest seeds in the plant world, often compared to fine dust or ground pepper. Because they are so tiny, handling them requires a gentle touch and a bit of strategy. If you open a seed packet in a breezy room, the seeds could easily blow away before you even get them to the soil.

To make things easier, many seed companies offer "pelleted" seeds. These are regular begonia seeds coated in a thin layer of dissolvable clay or starch. This coating makes the seeds large enough to see and handle with your fingers or a pair of tweezers. Pelleted seeds are much easier to space out evenly in your planting trays, which saves you work later when it is time to thin or transplant the seedlings.

If you are using raw, non-pelleted seeds, you might find it helpful to mix them with a small amount of very fine, dry sand. This helps "bulk up" the seeds so you can sprinkle them more evenly across the surface of your soil. Regardless of which type you choose, remember that these tiny seeds have very little stored energy, so they need perfect conditions to get a strong start.

When to Start Your Begonia Seeds

Timing is one of the most important factors when learning how to grow begonias from seed. Unlike marigolds or zinnias, which grow very quickly, begonias are slow starters. They take their time to develop a strong root system and their first few sets of leaves. For most parts of the United States, the best time to sow begonia seeds is between mid-January and early March.

Starting this early ensures that your plants are large enough to begin blooming by the time the weather warms up in late May or June. If you wait until April to sow your seeds, you may not see flowers until very late in the summer. Begonias generally need about 12 to 16 weeks of indoor growth before they are ready to be moved into the garden.

Keep in mind that your local climate and your "last frost date" will dictate your exact schedule. You want your seedlings to be robust and well-established by the time the danger of frost has passed. Because we ship our tubers from our facility in Lakewood, New Jersey, based on hardiness zones, we always recommend checking your local frost dates to ensure your timing is just right for your specific area.

Essential Supplies for Success

Before you begin, gather all your supplies so the process goes smoothly. Having everything ready to go will help you maintain the sterile environment these delicate seeds require.

• Fresh, sterile seed-starting mix: Do not use garden soil or old potting mix. Begonia seedlings are susceptible to "damping off," which is a common soil fungus that can cause young stems to rot at the soil line. A fresh, soil-less mix is light and free of pathogens.
• Shallow planting trays or containers: You can use specialized seed flats or even clean, recycled plastic containers with drainage holes poked in the bottom. Drainage simply means how fast water leaves the soil; good drainage is essential to prevent rot.
• A clear plastic dome or plastic wrap: This helps hold in humidity, creating a mini-greenhouse effect that keeps the seeds from drying out.
• Grow lights: Begonia seeds need a lot of light to germinate and grow. A sunny windowsill is rarely enough during the short days of winter. Shop lights or dedicated grow lights are much more reliable.
• A heat mat: Begonias love warmth. A waterproof seedling heat mat placed under your trays will keep the soil at a consistent temperature, which speeds up germination.
• A fine-mist spray bottle: Since the seeds are so small, a regular watering can will wash them away. A mister allows you to keep the soil moist without disturbing the seeds.

Key Takeaway: Using sterile mix and providing consistent heat and light are the three most important steps for successfully starting begonia seeds.

Preparing the Growing Medium

Start by placing your seed-starting mix in a clean bucket and adding warm water. Stir it until the mix is evenly moist but not soaking wet. A good rule of thumb is that the mix should feel like a wrung-out sponge. If you squeeze a handful, only a few drops of water should come out.

Fill your trays or containers with the moistened mix, leaving about half an inch of space at the top. Gently press the soil down to create a flat, even surface. Avoid packing it too tightly; you want the tiny roots to be able to penetrate the soil easily as they grow.

If you are worried about cleanliness, some gardeners choose to sterilize their mix even further by pouring boiling water over it and letting it cool completely before planting. While not always necessary with a fresh bag of high-quality mix, it can provide an extra layer of protection for these sensitive plants.

How to Sow Begonia Seeds Step-by-Step

Once your trays are prepared, it is time to sow the seeds. This part of the process requires focus and a steady hand.

1. Distribute the seeds: If you have pelleted seeds, place them on the surface of the soil about one inch apart. If you have raw seeds, sprinkle them as evenly as possible across the surface.
2. Do NOT cover the seeds: This is the most common mistake gardeners make. Begonia seeds need light to germinate. If you cover them with soil, even a thin layer, they will likely fail to sprout.
3. Press them in: Use your fingertip or a flat piece of cardboard to very gently press the seeds into the surface of the moistened soil. You aren't burying them; you are just making sure the seed has good contact with the soil.
4. Mist the surface: Use your spray bottle to give the surface a light misting. This helps "settle" the seeds and, if you are using pelleted seeds, it begins to dissolve the coating so the seed can access moisture.
5. Cover the tray: Place your clear plastic dome or a sheet of plastic wrap over the tray. This locks in the moisture so you don't have to water again until after the seeds sprout.

Providing the Right Environment for Germination

Now that your seeds are sown, they need the right "weather" to wake up. Begonias are tropical plants by nature, so they thrive in warm, humid conditions.

Place your trays on a heat mat set to approximately 70°F to 75°F. If the room is particularly cold, you might need to set the mat slightly higher. Consistent soil temperature is much more important than the air temperature in the room.

Position your grow lights about 2 to 3 inches above the top of the humidity dome. Leave the lights on for 14 to 16 hours a day. You can use a simple plug-in timer to automate this. If the lights are too far away, the seedlings will become "leggy," meaning they grow tall and weak as they stretch toward the light.

Germination can take anywhere from 10 days to 3 weeks, depending on the variety and the conditions. Don't be discouraged if you don't see anything right away. Check the trays daily to ensure the soil surface hasn't dried out. If it looks dry, give it another light misting.

Caring for Begonia Seedlings

Once you see tiny green specks appearing on the soil surface, the seeds have germinated! This is an exciting moment, but your work isn't done yet. As soon as most of the seeds have sprouted, you should remove the plastic dome or wrap. This allows for better air circulation and prevents mold or rot from developing.

Continue to keep the soil moist, but be careful not to overwater. At this stage, it is often better to water from the bottom. Place your seedling tray into a larger tray with an inch of water and let it soak up moisture through the drainage holes for about 10–15 minutes. This keeps the delicate stems and leaves dry while ensuring the roots get what they need.

As the seedlings grow, you will need to raise your grow lights to keep them about 3 to 4 inches above the tops of the plants. If the leaves start to look a bit pale, you can begin using a very weak, water-soluble fertilizer. Use it at about one-quarter of the strength recommended on the label once every two weeks.

Transplanting Into Larger Pots

When your begonia seedlings have at least two sets of "true leaves" (the leaves that grow after the initial seed leaves), they are ready for more space. This usually happens when the plants are about an inch tall.

1. Prepare new containers: Fill small 3-inch pots or "four-pack" nursery cells with fresh potting soil. Moisten the soil before you start.
2. Lift carefully: Use a small spoon or a popsicle stick to gently lift the seedling out of the starting tray. Avoid pulling on the stem, as it is very easy to bruise. Instead, lift from underneath the roots.
3. Replant: Make a small hole in the new pot, tuck the roots in, and gently firm the soil around the base. The plant should be at the same depth it was in the starting tray.
4. Water in: Give them a light watering to help settle the roots in their new home.

After transplanting, your begonias will likely go through a "growth spurt" now that they have more room for their roots to expand. Keep them under the grow lights and continue your light fertilization routine. For more detailed advice on moving plants at the right time, see Can Potted Begonias Be Planted Outside?.

Pinching and Shaping Your Plants

If you want your begonias to be full and bushy rather than tall and thin, you can "pinch" them. This is a simple technique where you remove the very top tip of the main stem once the plant has about 6 to 8 leaves.

By removing the tip, you signal the plant to put its energy into growing side branches. This results in a much more attractive, mounded shape that will produce more flowers throughout the season. This is especially helpful for wax begonias and trailing varieties used in hanging baskets.

Pinching might feel like you are setting the plant back, but it is a "short-term wait for a long-term gain." Within a week or two, you will see new growth emerging from the leaf joints below where you pinched, leading to a much sturdier plant.

Hardening Off and Moving Outdoors

You cannot move begonias directly from the warm, protected environment of your home to the garden without a transition period. This process is called "hardening off." It allows the plants to gradually get used to the wind, direct sun, and temperature changes found outdoors.

Wait until all danger of frost has passed and the nighttime temperatures are consistently above 50°F.

• Day 1-2: Place your pots in a fully shaded, sheltered spot outside for 1 to 2 hours, then bring them back inside.
• Day 3-4: Increase the time to 3 or 4 hours, and allow them to get a tiny bit of dappled morning sunlight.
• Day 5-7: Increase the outdoor time by a couple of hours each day, gradually moving them into more light (if the variety prefers sun).
• Day 8-10: If the weather is mild, you can leave them out all day and even overnight.

Keep a close eye on the soil during this time. Small pots dry out much faster outdoors in the breeze than they do inside. If a cold snap is predicted, bring them back indoors immediately. For more on this transition, see our begonia moving tips.

Choosing the Best Spot in Your Garden

Begonias are versatile, but matching the right plant to the right place is the key to a beautiful display. Our team at Longfield Gardens evaluates many different types in our trial gardens to see how they perform in various conditions.

• Wax Begonias: These are the most common bedding begonias. They have fleshy, shiny leaves and can handle a fair amount of sun, though they appreciate some afternoon shade in very hot climates. They are excellent for mass plantings or borders.
• Tuberous Begonias: Known for their massive, rose-like blooms, these prefer partial to full shade. They are prone to stem breakage in high winds, so pick a sheltered spot like a covered porch or a protected corner of the garden. If you want to shop this type, the Upright Double Begonias collection is a good place to start.
• Rex and Foliage Begonias: These are often grown for their incredible leaves rather than their flowers. They do best in full shade and make stunning accents in container gardens.

Regardless of the variety, all begonias need well-draining soil. If your garden soil is heavy clay, consider growing them in raised beds or containers where you can control the soil quality more easily. For a deeper overview of begonia care and placement, see All About Begonias.

Caring for Your Mature Begonias

Once your begonias are settled in the garden, they are relatively low-maintenance. However, a little consistent care will keep them blooming until the first frost of autumn.

Watering: Begonias like consistent moisture but hate being soggy. Water when the top inch of soil feels dry to the touch. In the heat of summer, containers and hanging baskets may need water every day. Try to water at the base of the plant to keep the foliage dry, which helps prevent powdery mildew.

Feeding: Flowering takes a lot of energy. Use a balanced liquid fertilizer every two to three weeks to keep the blooms coming. If you are growing them in containers, the nutrients in the potting soil will wash out over time, so regular feeding is even more important.

Deadheading: This is the process of removing faded flowers. While many modern wax begonias are "self-cleaning" (meaning the old flowers fall off on their own), tuberous begonias benefit from manual deadheading. This keeps the plant looking tidy and encourages it to produce more buds rather than putting energy into seed production.

What to do next:

• Order your seeds early to ensure the best variety selection.
• Check your grow light bulbs to make sure they are bright and functional.
• Mark your calendar for late January to start your sowing project.

If you'd like to compare finished plants instead of starting from seed, browse the Begonia Hanging Pink Balcony tubers for a trailing look that works beautifully in pots and baskets.

Storing and Saving Your Own Seeds

If you fall in love with a particular non-hybrid variety you've grown, you can try saving your own seeds for next year. Wait until the seed pods on the plant are completely dry and brown. They will often start to split open on their own when they are ready.

Carefully snip the pods and hold them over a white piece of paper. Tap the pod, and the dust-like seeds will fall out. Because they are so small, you should store them in a small glassine envelope or a folded piece of parchment paper. Avoid plastic bags, as the seeds can get stuck in the corners or cling to the sides due to static electricity.

Label your seeds with the variety name and the date you collected them. Store them in a cool, dry, dark place. A lidded jar in the refrigerator is often the best spot to keep seeds viable for several years. Keep in mind that seeds saved from hybrid plants (often labeled as "F1" on the packet) will not grow "true to type," meaning the new plants might look different from the parent.

Conclusion

Growing begonias from seed is a patient but deeply rewarding journey. From that first tiny sprout in mid-winter to the final explosion of color in your summer garden, you will have the satisfaction of knowing you raised those plants yourself. By focusing on the basics—sterile soil, plenty of light, and a warm environment—you can achieve professional-looking results right in your own home.

At Longfield Gardens, we take pride in providing the quality plants and practical advice you need to create a beautiful landscape. Whether you are starting from seed or planting our premium tubers, we stand behind our products with a 100% quality guarantee. We want every gardener to feel confident and successful in their growing endeavors. If you want to review our policies before you shop, visit our shipping information page.

As you look forward to the coming season, remember that gardening is a journey of discovery. Every seed you plant is a new opportunity to learn and grow.

• Start your seeds in January or February for a full season of blooms.
• Never cover begonia seeds with soil; they need light to germinate.
• Use a heat mat to maintain a steady soil temperature of 75°F.
• Hardening off is essential for a smooth transition to the outdoors.

We encourage you to try at least one new begonia variety this year; the results are sure to bring a smile to your face and beauty to your home.

FAQ

How long does it take for begonia seeds to germinate?

Begonia seeds typically take between 10 and 21 days to germinate, though some varieties may take up to a month. Providing consistent bottom heat and high humidity will help speed up the process. If you don't see sprouts after three weeks, check your soil temperature and ensure the seeds are receiving enough light. If you want a broader reference for begonia types and timing, return to All About Begonias.

Do I need to cover begonia seeds with soil?

No, you should never cover begonia seeds with soil. They are "light-germinating," meaning they require exposure to light to trigger the growth process. Simply press them gently into the surface of the moistened seed-starting mix to ensure good contact, but leave them visible on the surface.

Why are my begonia seedlings growing so slowly?

Begonias are naturally slow growers in their early stages. They spend a lot of energy developing a healthy root system before they put on significant top growth. Ensure they are getting 14–16 hours of bright light and a weak fertilizer every two weeks to support their development as they grow. For help matching plants to the right exposure, see Where to Plant Begonias: Sun or Shade?.

Can I grow begonias from seed without grow lights?

While it is technically possible, it is very difficult to grow healthy begonias from seed using only natural window light. Because the seeds must be started in the middle of winter when days are short and the sun is low, seedlings often become weak and leggy. Using a simple shop light or grow light greatly increases your chances of success. For more on container care after transplanting, see Can Potted Begonias Be Planted Outside?.