11 Common Problems With Flowering Begonia Plants
If your begonias are struggling this season, you've come to the right place! Begonias can have many common issues during their lifespan, so it's important to identify common problems early and remedy them as fast as possible. In this article, certified master gardener Laura Elsner looks at the most common issues that plague begonias, and how to fix them.
Begonias are no longer just the flower’s in your granny’s garden. There are so many types and varieties of begonias that it is no wonder they’ve been making a resurgence in both indoor and outdoor gardens. Of course, like with all plants, things can go awry.
Begonias are well known for being low-maintenance flowers. It’s one of the reasons they are so appealing, no matter how your begonias are grown. Unfortunately, many gardeners mistake low-maintenance with “no maintenance” and that’s where problems start.
If your begonia has started to struggle, or you’ve run into some issues with your plant and aren’t sure what to do, you’ve come to the right place. Follow along as we dig into the most common problems with begonias, and how to fix them!
This is a big one. When your begonias aren’t blooming, this usually signals that there’s something wrong with the plant. There could be a variety of different issues that cause a lack of blooms. Let’s look at the most common three, which include type of plant, lack of sun, or overwatering your plant.
I am going to get a more obvious reason out of the way first. Some varieties of begonias are known for their blooms, while others are prized for their foliage. Wax and tuberous varieties are the begonias we typically prize for their blossoms.
Rhizomatous varieties are more prized for their foliage. Rhizomatous begonias include rex begonias, which have gorgeous foliage, and smaller, less showy, blossoms for the most part. So if blossoms are what you are after, choose a wax, tuberous, or a combination of the two, known as a rieger begonia.
A good guide to follow is to purchase flowering begonias in the bedding out plants section of a garden center. Look for foliage focused begonias in the houseplant or tropical section of the garden center.
Not Enough Sunlight
While begonias are shade plants, too much shade will cause them to stop blooming. You want at least 4-6 hours of sun on them.
Any less and they will cease to bloom, or have far fewer flowers then they would in more sun. If you do have a very shady area, opt for a rex variety that will provide bright cor through foliage rather than blooms.
Begonias do not tolerate being in wet soil. They will simply rot. This will also cause them to lose their flowers. Test your soil by sticking your finger into it. It should feel moist but not soggy.
Brown, Crispy Leaves
Crispy brown leaves is another common problem you’ll likely encounter. It can be caused by a few different things. Once you identify the cause, it can be remedied. Let’s look at the most common reasons this happens.
Too Much Sun
While I just went over what happens when begonias don’t get enough sun (they don’t bloom), too much sun can be equally detrimental. If your plants are looking crispy or have crispy edges, look at how much sun they are getting. Full sun conditions, 6+ hours, is usually too harsh.
There are a few exceptions, there is a series called Solenia, which can handle full sun. Or wax varieties especially those with bronze cor leaves like that of the Olympia series that will grow happily in full sun conditions.
For indoor begonias, place in a spot with bright indirect sun. Placing them in a window that receives too much direct sun can cause the leaves to get crispy. If this happens try moving your plant back from the window.
I actually find begonias to be quite forgiving when it comes to under watering them. However, if you neglect them for too long the leaves will get crispy.
Keep the soil evenly moist, not soggy. Use a light fluffy soil so they can absorb and drain water freely. Avoid allowing your begonia to dry out completely, this will cause them to start getting crispy, as mentioned earlier.
This one is especially true for begonias grown as houseplants. The dry air in our homes can make their leaves brown and crispy. First, make sure you do not have your plant placed near an air vent. Dry air constantly blowing on your begonia will turn it crispy.
Next, try adding humidity near your plants. A tray with pebbles filled with water placed underneath your begonia will provide a bit of extra humidity. Alternatively, you can purchase a humidifier. Place it near your plants. It will boost humidity and keep your houseplants happy.
If you find your begonia stems are rotting it is likely a watering and drainage issue. The stems are mushy and the whole plant will break off at the stem.
Stem and root rot is caused by a bacteria that thrives in damp conditions. Once your plant has stem rot, there is not much that can be done. Throw away the soil and disinfect any tools you were using on the plant.
To avoid rotting stem, make sure you are not over watering and that the container you have your begonia in has adequate drainage holes. Soil should feel moist, but not wet.
For begonias planted directly in the garden, make sure you have a bit of space between each plant for airflow. Amend the soil so it is light and fluffy. You may need to add peat moss or coconut coir before planting. Do not plant them in a low lying boggy area.
Also, when planting them in a container, plant the crown level with the rim of the pot. Don’t plant the crown below the rim of the pot, this creates a damp environment around the stem of your begonia and invites root rot bacteria.
Yellow leaves is a classic sign of overwatering. If the leaves near the base are fading to yellow and falling off check the amount of water. The soil should feel moist but not wet or soggy.
Make sure you are using a nice light fluffy potting mix for potted begonias. Also, make sure your container has adequate drainage holes. Placing pebbles in the bottom is not enough.
For garden begonias, it is harder to control water because of the rain. Amending soil with peat or coconut coir will help with the absorption of excess water so the soil and plant don’t get waterlogged. Also, don’t plant them in the naturally boggy areas of your garden.
White Spots on Leaves
Usually, white spots on the leaves mean you are dealing with powdery mildew. Powdery mildew is a fungus. It is a powdery film that coats the leaves of plants. It will stunt the growth and can eventually kill your begonias if left untreated.
Over-watering can cause mildew. The overly wet conditions is a breeding ground for powdery mildew. Make sure the soil is evenly moist but not soggy and wet. When watering also try not to spray the foliage with water.
For container begonias, I recommend bottom watering. Leave the plant in a tray of water and let it suck the water up through the drainage holes. Discard the excess water. This will ensure even watering and lessen the chance of powdery mildew.
For garden begonias, I like snaking a drip hose through the garden and watering at soil level instead of overhead sprinklers. If you are overhead watering, try and do it in the early morning as opposed to evening.
That way the water on the leaves will quickly dry in the sun as opposed to having the foliage sit wet all night. Wet foliage is a breeding ground for powdery mildew.
Spacing of plants is also a consideration. Leave space between them to allow for airflow between the plants. If you have detected mildew, you can purchase a fungicide at the garden center. Spray as directed. Then work on prevention.
If the mildew is really bad, I sometimes toss the plant and start over. Replace the potting soil with fresh new soil so as to not reinfect the new plant.
Little White Bugs
If you notice mottled leaves and a silky webbing on your plants with little white bugs, take a closer look. Tiny spider-like insects, spider mites, might be infesting your plants. If this is a houseplant, move it away from your other plants.
They spread like wildfire. Start by wiping or washing the leaves and stems of the plant. For outdoor plants, try a blast of the hose. Be careful using insecticidal soap. Begonias are sensitive to it. Spot test a leaf and wait 24 hours to see if the leaf wilts from the insecticidal soap.
Sudden Plant Death
Begonias are not frost hardy. If your plants are beautiful one day and then laying limp on the ground the next, you may have had a frost in your area. Even low temperatures without frost will take its toll.
The leaves will be nipped and brown and they will slowly die. They need temperatures above 50F (10C) to thrive. Pay attention particularly to night temperatures. This is more important in the spring than fall. I find newly planted begonias are more susceptible than established ones. But once a frost hits they will die.
If you live in an area where you only encounter an occasional frost, cover your plants with a sheet or frost cloth. Don’t use tarps or plastic, they don’t protect from frost.
Stunted growth can be a sign that your begonia is not getting enough nutrients. They are heavy feeders, especially the ones with big beautiful flowers.
For begonias grown in the garden make sure you are amending your soil prior to planting. Top dress garden beds in the fall or spring. You can use compost, aged manure, worm castings, or sea soil. No need to dig it into the soil. The nutrients will seep down over time.
For container grown begonias I start with a nice light fluffy potting soil. Then I fertilize. Outdoor containers I fertilize every two weeks in the summer months. An all-purpose 20-20-20 works great. You can also top dress containers with some worm castings.
For indoor plants, again I start with light fluffy potting mix. Then I fertilize every two weeks during the active growing season. I don’t fertilize in winter when they are dormant. A 20-20-20 works great. I tend to use a liquid fertilizer for my indoor plants.
Irregular brown lesions on the leaves of your begonia is not a good sign. This could be caused by foliar nematodes. Unfortunately, there is no treatment for them. Dispose of the plant to limit spreading. Do not put it in your compost.
Make sure you rule out other possibilities before diagnosing with foliar nematodes. Read number two to rule out any other causes of crispy, brown leaves.
Leaves With Holes
Begonias love moist shady gardens, so do slugs and snails. If you notice holey leaves and trails of slime, look for slugs and snails. These slimeball pests love to feast on foliage.
There are some options to control slugs and snails. You can hand-pick them. This is best done in the early morning or the early evening. It’s time-consuming but oddly satisfying.
You can sprinkle crushed eggshells or diatomaceous earth (which can be purchased at garden centers) around your begonias. The sharp shards will cut up the slugs and snails. They won’t cross them to get to the plant. This will have to be reapplied after heavy rains or tilling the soil.
The beer method works for catching slugs and snails. Fill shallow trays with beer and leave them in the garden. Empty the trays every morning or evening and refill as needed.
Slug bait also works. It is toxic to dogs, so use with caution, but it works. Sprinkle it throughout your garden. The slugs will disappear.
Plants Look Like They Were Eaten
If the begonias in your garden just appear to be eaten. It’s probably deer. Deer love the blossoms of begonias and will eat their fleshy tubers happily. There are a few ways to deter deer.
The variety you’ve chosen will impact if deer will snack on them. Wax begonias with waxy or fuzzy leaves are generally avoided by deer (I say this, but a hungry deer will snack on almost anything).
Another great deterrent is simply keeping them out of reach. Hanging baskets of a hanging variety of begonia is a great way to enjoy those shady blooms without pesky deer.
Using sprays that will deter deer, or sprinkling blood meal around the garden will also deter them, keep in mind it will need reapplied after rain or sprinklers.
Begonias are loved by both gardeners and houseplant enthusiasts. It’s one of the few plants everyone can agree on. Keeping them healthy and happy is simple for the most part. If you run into troubles, hopefully, these 11 tips will get you back on track to growing healthy and beautiful begonias.