11 Tips to Keep Your Begonias Blooming all Season Long

Begonias are one of my favorite flowers in the garden. I love them in the ground or growing in containers. The huge blossoms on tuberous begonias are hard to beat. The small but profuse blossoms on wax begonias are eye-catching as well. There are also hybrids of the two and delicate hanging varieties that add color and interest to the garden.

If you’ve come here looking to maximize the blooms of your garden grown begonias this season, you’ve landed in the right place. Begonias are hardy plants, but there’s a few tricks you can employ at your disposal in order to keep them blooming all season long.

Ready to learn a little more about extending the bloom times of your begonias? In this article, I’ll share my top tips for keeping your beautiful begonias blooming all summer. Let’s dig in!

Water, But Not Too Much

I am starting out this list with what I think is the most important factor for getting begonias to bloom.  Water. If someone were to ask me why their begonias aren’t blooming it would be the first thing I’d ask. Unlike most flowers which I would immediately say water more. Begonias don’t need, or like, a heavy hand at watering.

Begonias can actually handle light periods of drought. Their tuberous stems hold water. I wouldn’t go too long without giving them a drink. But over watering them is certain death to begonias and their blooms. It will lead to brown rotten blooms and rotting stems.

I will actually say under watering is far less detrimental than overwatering them. Under-watered begonias will actually bloom more than overwatered plants. But I recommend just keeping them evenly moist for the best long term outcome.

Give Them Adequate Sun

While begonias are most often thought of as shade flowers, they do require a bit of sun to get them blooming. I think around 4 hours of early morning sun is perfect. Too much and the flowers and leaves will fizzle.

But not enough and there will be little to no blooms and the plant will be reaching and appear leggy. Tuberous begonias are often touted for their ability to handle deep shade, but I find they don’t have as many spectacular blooms on them when they receive no direct sunlight.

If you do have a very shady area of your garden that receives no sun and still want to plant begonias, try planting rex begonias, or a variety that relies on its foliage to add interest as opposed to its blooms.

There are some varieties, such as the Solenia series that can actually take full sun conditions. These bloom spectacularly when all their requirements are met.

Use Light Soil

Heavy soil will cause begonias to rot and turn yellow. To determine how heavy your soil is I like to use this simple trick. Grab a handful of garden soil and squeeze it into a ball. If the ball stays intact when you release it, you have heavy clay soil. The soil should just crumble away back to shapeless soil.

Heavy clay soil will limit the amount of blossoms on your plant. It holds onto water and will cause yellowing leaves and rotting stems.  Amend garden soil with coconut coir or peat. If growing begonias in containers, use a nice light and fluffy potting mix.

Fertilize Them Regularly

Fertilizer is the special sauce for flowering annuals. I design, plant, and care for a lot of annuals every season. Anyone I plant for will often comment on how much more their plants bloom after I’m finished.

But I’ll tell you one of my secrets. I fertilize. A lot. I use an all purpose 20-20-20 powder dissolved in water once every 2 weeks.

This will make all of your flowering annuals bloom. Don’t believe me, do the experiment. Plant two identical pots and place them in the same sun conditions. Give one fertilizer and one nothing. You’ll notice the difference.

Make sure to never fertilize dry plants. Water them first and then apply fertilizer. Applying fertilizer to dry plants will burn them. I also don’t fertilize until 2 weeks after I first plant them. Let the roots settle and establish first.

If your begonias are stressed in any way (it’s too hot, too damp, mildew, pest etc) fertilizer is not a miracle fix. It works best on already healthy plants.

Use a High Quality Compost

If you are planting lots of garden beds full of begonias and you want to make them bloom, amend the beds with compost, manure, or worm castings before planting.

I usually just top dress the beds. Make sure the soil is light and fluffy and then add the compost. This is slow release and will help with blooms throughout the season.

Deadhead When Needed

This is another important one when it comes to begonias. Especially the tuberous or reiger varieties. These large flowers should be removed as soon as they start looking brown and shabby.

I snap (or snip) off the entire stem to the base of the plant to promote the growth of new blossoms. I remove any yellow or brown or poor looking leaves. This way the plant can put its energy into producing new, healthy growth.

I will also pinch back any leggy growth so the begonia will remain compact and bushy. Too much legginess in a plant is usually a sign it isn’t getting enough sun.

Choose The Right Varieties

This one may seem obvious to some people. But a newbie gardener may not know the differences in begonias. There are many, many varieties of begonias.

The rhizomatous varieties of begonias (which includes the very popular rex begonia varieties) are not known for their blossoms. They are known for their intricate foliage designs and colors. They bloom usually a small nondescript string of white. If it is blooms you are after, rhizomatous begonias are not the right variety for you.

Wax or fibrous begonias are small. These are the old fashioned flowers that give begonias that nostalgic feeling of grandma’s garden. They bloom profusely. The blooms are small and the plant is usually short. These should be planted in masses for more impact and more showy blossoms.

Tuberous begonias are my favorite. These are the big rose-like blooms that hang from chunky tuberous stems. They are the most spectacular blossoms and are what come to mind when I think of begonias. Plant these begonias if you want mega blooms.

Reiger begonias are the love child of wax and tuberous begonias. These are actually an amazing bloom. They sit upright in rosettes on top of the plant and have thick sturdy leaves. I love these because they seem to just remain in bloom all season and require little to no deadheading. They also seem to do better in deep shady areas for blossoms than tuberous ones (from my experience).

While this isn’t a scientific classification, I also like to mention hanging begonias. Most of these are tuberous varieties (some are wax). But these begonias are different because they dangle down. I find these varieties particularly showy and covered in blossoms all season long.

Pick a Proper Location

Begonias like a nice warm and sheltered location. If you are planting them in a wide open area, I recommend planting wax or rieger begonias. Their leaves and blossoms are a lot sturdier than tuberous begonias. Tuberous begonias will shred and wilt in exposed conditions.

I like planting in shelter areas, around decks and patios for instance. Or perhaps in containers or a sheltered garden bed full of hostas and ferns who also dislike winds and bad weather.

I also like planting them under overhangs or large trees. While it might mean I have to water more often, it also means I am in control of the water, and therefore won’t give them too much. It also means that the leaves and delicate flowers aren’t getting beaten down with a lot of heavy rain.

Watch Your Temperature

Begonias do not like temperatures below 50F (10C). They also do not like cold soil. Keep an eye especially on night temperatures and wait until they are consistently above 50F before planting them. Planting them sooner to get a jump on the season will only stunt them, if they survive at all.

Deal With Mildew Right Away

Powdery mildew seems to be attracted to begonias. The combination of damp shady areas and no wind make ideal conditions for the powdery mold to form. This powdery substance coats the leaves and stunts the flower production.

Powdery mildew is a white powdery film that forms on plants. It is a fine dust that can be wiped away. It stifles plants and will soon kill them if it is not treated.

This is a big reason to not overwater and to not keep them in deep shady conditions. Adequate airflow is also important, so consider the spacing of the begonias. I find they rot and melt away when they are stuffed in too close.

If you have powdery mildew go ahead and spray them with a copper fungicide. But next time you go to plant, try and amend the conditions so as to avoid the mildew in the first place.

Containers Are Your Friends

Containers are your friend when it comes to begonias. The soil is lighter (make sure to only use potting soil), and the conditions are easier to manage. I find my begonias, especially the spectacular tuberous varieties, bloom a lot more when they are in containers.

Make sure your containers have adequate drainage so that excess water does pool in them.