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When to plant begonias depends on your climate, your growing zone, and whether you’re starting with tubers, bulbs, or young plants.
The simple answer is that you should plant begonias outdoors only after all danger of frost has passed, because these beauties simply can’t handle cold temperatures.
For most gardeners, that means waiting until late spring, usually two to three weeks after the last expected frost date in your area.
But there’s more to getting the timing right, because you also need to consider starting begonias indoors if you want earlier blooms.
In this post, we’ll break down exactly how and when to plant begonias, whether you’re growing tuberous, wax, or rex begonias, and what conditions they need to thrive.
Let’s dig into the details so you can enjoy a vibrant, flourishing begonia display all season long.
When To Plant Begonias: The Essential Timing Guide
When to plant begonias really comes down to two separate moments: the indoor start date and the outdoor transplant date.
If you’ve ever wondered when to plant begonias for the best results, the answer involves working backward from your local frost calendar.
Here’s how to get the timing just right for both methods.
1. Start Begonia Tubers Indoors 8 to 12 Weeks Before the Last Frost
Tuberous begonias are the showstoppers with big, rose-like flowers, and they need a head start indoors to bloom in summer.
You should plant begonia tubers indoors about 8 to 12 weeks before your last expected spring frost date.
For example, if your last frost is around May 15, you’d start your tubers in late February or early March.
To start them, place the tubers with the hollow side facing up in a shallow tray filled with moist potting mix.
Keep the tray in a warm spot around 70°F, and lightly mist the soil to keep it slightly damp but never soggy.
Once you see sprouts emerging, which usually takes two to four weeks, move the tray to a bright windowsill or under grow lights.
This indoor start gives your begonias a massive head start, and they’ll be ready to explode with color once they hit the garden.
2. Plant Begonias Outdoors After the Last Frost Has Passed
When to plant begonias outside is non-negotiable: wait until nighttime temperatures stay consistently above 50°F.
Even a light frost can kill begonia foliage and tubers instantly, so don’t rush it.
Check your local frost dates and add an extra week of buffer just to be safe, because cold soil can also stunt their growth.
For most zones, this outdoor planting window falls between mid-May and early June.
If you’re planting container-grown begonias from a nursery, you can plant them out at the same time as tubers, as long as the soil has warmed up.
The key is to harden off your indoor-grown begonias first, which means gradually exposing them to outdoor conditions over 7 to 10 days.
Start with a few hours of morning shade, then slowly increase their time outside and their exposure to direct sun.
This prevents transplant shock and keeps your begonias from dropping leaves when they move to the garden.
3. Consider Your Growing Zone for Exact Planting Months
Knowing when to plant begonias also depends heavily on where you live.
In USDA zones 9 to 11, where winters are mild, you can often plant begonia tubers directly in the ground in early spring, around March or April.
In zones 7 and 8, you’ll typically start tubers indoors in March and plant begonias outside in May.
In colder zones 3 to 6, you’ll need to start your tubers even earlier, around February, and transplant them out in late May or early June.
If you’re growing begonias as annuals in northern climates, you can simply buy started plants and set them out once the frost danger is fully gone.
How To Plant Begonias: Step-by-Step for Success
Now that you know when to plant begonias, let’s talk about the actual planting process.
Whether you’re planting tubers, transplants, or bedding begonias, the following steps will help you get them off to a great start.
1. Choose the Right Location for Your Begonias
Begonias aren’t too fussy, but they do have strong preferences when it comes to light.
Most begonias, especially tuberous types, prefer partial shade with dappled morning sun and afternoon shade.
Wax begonias can handle more sun, but they still appreciate some protection from harsh afternoon rays.
The soil should be well-draining, rich in organic matter, and slightly acidic with a pH around 5.5 to 6.5.
If your soil is heavy clay, mix in some compost or peat moss to improve drainage before planting.
2. Plant Tubers at the Correct Depth and Spacing
When you’re planting begonia tubers directly outdoors, dig a hole about 1 to 2 inches deep.
Place the tuber with the concave, hollow side facing upward, because that’s where the stems will sprout from.
Cover lightly with soil and water gently to settle the tuber into place.
Space tubers about 12 inches apart for most types, but larger tuberous begonias may need up to 18 inches.
For container planting, choose a pot with drainage holes and use a high-quality potting mix.
Plant one tuber per 6-inch pot, or space multiple tubers 6 inches apart in a larger container.
3. Water and Mulch Properly
Begonias like consistent moisture but absolutely hate sitting in waterlogged soil.
Water deeply after planting, then keep the soil evenly moist, allowing the top inch to dry out between waterings.
Applying a 2-inch layer of organic mulch around your begonias helps retain soil moisture and keeps the roots cool.
Avoid mulching directly over the crown of the plant, since that can lead to stem rot.
During hot summer weeks, check your begonias daily, because containers dry out faster than garden beds.
Tips For Planting Begonias In Containers
Many gardeners prefer to plant begonias in pots, and honestly, they thrive in containers.
When you plant begonias in containers, you get more control over the soil, moisture, and light conditions.
Here are a couple of container-specific tips to keep in mind.
1. Use a Loose, Well-Aerated Potting Mix
Begonias need good airflow around their roots, so avoid heavy garden soil in pots.
Instead, use a light potting mix that contains perlite or coarse sand to ensure excellent drainage.
You can also mix in a bit of compost for slow-release nutrients.
Make sure your container has at least one drainage hole, because even one night of soggy roots can kill a begonia.
2. Fertilize Begonias Every Few Weeks
Begonias are moderate feeders, especially when grown in containers where nutrients wash out quickly.
Start fertilizing about two weeks after planting with a balanced, water-soluble fertilizer like a 10-10-10 mix.
Dilute it to half strength and apply every two to four weeks during the growing season.
Reduce feeding in late summer as growth slows, and stop fertilizing entirely once the foliage starts to die back.
So, When To Plant Begonias For The Best Blooms?
When to plant begonias is all about timing, patience, and understanding your local climate.
You should plant begonias outdoors only after the last frost, and start tubers indoors 8 to 12 weeks before that date.
The ideal moment is when nighttime temperatures stay above 50°F and the soil has had a chance to warm up.
Whether you’re planting begonias in garden beds, hanging baskets, or patio containers, the same rules apply.
Give them the right start, consistent moisture, and a spot with their preferred light, and they’ll reward you with months of gorgeous color.
By following this guide on when to plant begonias, you’ll avoid the heartbreak of frost damage and enjoy a thriving, vibrant display from early summer all the way into fall.
So mark your calendar, prepare your tubers in advance, and get ready to watch your begonias flourish.