Why Are My Begonia Leaves Turning Brown? (Solved!)


Begonias are renowned for their dramatic, colorful foliage. Your indoor begonia sports leaves that are spotted, speckled, green, white, or even purple – but brown is not what you want at all.

Begonias come in a variety of colors and textures depending on the variety, and all of them can go brown if they aren’t cared for with diligence.

Brown leaves are often a sign of a thirsty plant or one that has become sunburned. Low humidity, poor nutrition, and fungal diseases are also likely to be the culprits. Begonia needs to be kept well-watered and away from direct sun to prevent its leaves from browning.

What Portions of Begonia Are Infected?

Before we can get to work fixing your begonia, we need to work out what’s going on.

Take a good look at your browning leaf. Is the browning at the edges or tips of the leaf? Perhaps your brown leaves are patchier, with areas of browning scattered over the leaf.

Are the brown patches soft, or are they crunchy and dry? Are there other parts of the plant that have unusual growths, textures, or smells?

Each type of browning has its own clues as to its cause. Let’s see what’s causing your begonia to go brown.

Causes Of Brown Leaves in Begonias

 Begonia Leaves Turning Brown
Begonia Leaves Turning Brown

Under-watered Begonia

Probably the most common cause of browning in any indoor plant is a lack of water. If your begonia’s leaves are brown mostly at the tips and edges, with a distinct crunchiness, it’s likely you need to water it more often.

Begonias prefer gentle, consistent moisture. They don’t like to dry out entirely. Check your soil. If your pot feels light, the soil is dry and loose, and your poor begonia is wilting as well as browning then it’s time for a drink.

Solution

Thankfully under-watering is the easiest of all plant problems to fix. You simply give your begonia a thorough soaking!

To really give your darling a good drink, water from below. This will get moisture directly into the roots themselves without leaving the topsoil soggy and makes sure that the soil is holding the water well.

It’s important to avoid wetting their leaves directly, as begonias are vulnerable to fungal infections – more on that set of problems later.

To water from below:

  1. Place your begonia’s pot in a tray or basin at least half the height of the pot.
  2. Fill your tray with distilled, filtered, or rainwater to half the height of the pot.
  3. Allow the water to absorb into the soil through the drainage holes. Top up the water as the water level falls.
  4. Once the water level becomes stable, allow your plant to soak for a half-hour.
  5. Remove your pot from the tray. Allow the pot to drain for a further ten to fifteen minutes.
  6. Return your pot to its place. Check the drip tray or saucer periodically – if any more water flows through, discard.

To prevent under-watering, consider using a reminder set in your phone’s calendar. In the warmer parts of the year, your begonia will only need to be watered perhaps once a week at most.

During the autumn and winter, your begonia will enter a period of dormancy, and it may only need watering once a month!

Regardless of the season, the top inch of the medium in your begonia’s pot should be allowed to dry between watering.

I personally take an hour or so once a week to check in on my plants, inspecting the medium and roots and assessing if they require a drink.

Regardless of the season, the top inch of the medium in your begonia’s pot should be allowed to dry between watering. I check by poking my finger into the soil, but a moisture meter is a useful tool for those who like a bit more precision.

I personally take an hour or so once a week to check in on my plants, inspecting the medium and roots and assessing if they require a drink.

An alarm encouraging you to take time to enjoy your plants will benefit you too, even if you do not wind up needing to water.

Over-Watering and Root Rot

Overwatered Begonia

Very often an over-watered begonia will show the same signs of distress as an under-watered one. While this seems counter-intuitive, it comes down to how over-watering stresses and ultimately damages root systems.

Plants need aerated soil. Without a bit of oxygen in the soil, the roots drown. As they die off, the plant can no longer draw water from the soil.

The leaves begin to dry out, and your plant dies of thirst while swimming in moisture. In the very worst cases, your plant will rot from the roots up, an ignoble end to such a regal plant.

Over-watered leaves will brown in much the same way as under-watered ones, from the tip and edges inwards. Key differences are to be found in the pot.

If your soil is damp or wet, your pot is heavy, and liquid seeps from the drainage holes when you lift it, you’ve been too generous with the water and your plant is drowning.

Control and Management

First, you need to assess how bad the issue is. If caught early, you can allow your begonia to dry out before you water again.

But if your begonia has developed root rot, you will need to re-pot. Once the roots start to rot, the soil becomes a haven for pathogens that can put an end to your poor plant.

Signs to watch for are browning or blackened stems that are soft to the touch, foul-smelling potting medium, or soggy blotches on the leaves as they brown. You may well be in need of re-potting.

To re-pot your begonia;

  • Always use pots with plenty of drainage holes. Three is my preferred number, evenly distributed. If you plan to re-use your pot, clean it thoroughly in hot water and kitchen-grade disinfectant to kill any pathogens.
  • Use a free-draining potting medium. For begonias, a soil-free mix of equal parts perlite, vermiculite, and peat moss is ideal. If you do opt for a mix with soil in it, ensure there is plenty of organic material added for adequate aeration.
  • Remove your sick begonia from its pot, and carefully remove the sodden medium from around the root mass.
  • Inspect your roots. Any blackened, soft, or slimy roots need to be carefully cut away with clean scissors or shears. Some folks suggest rinsing roots with a weak solution of hydrogen peroxide, though I personally feel these risks further damage to the already stressed root system.
  • Once trimmed, your begonia can be put in its new, clean pot. Give it a good drink, and put it back in its spot.

Do not expect your begonia to immediately perk back up. Your plant will take some time to bounce back, so allow it time to recover from the shock of re-potting.

Begonias do not require a lot of water. While it may seem like neglect, only water when the top inch of the growing medium has dried completely.

As mentioned above, in the warm parts of the year this may be once a week or so, and during the winter you may go a month or more between rounds with the watering can.

For the over-watering gardener, an electric moisture meter can provide reassurance that your plant does indeed have enough water to survive.

Too Much Sun

Your begonia is a shade-loving plant. They do very poorly indeed in bright light, and direct sunlight can burn them to a crisp!

Unlike issues with water, begonia leaves burned from sun exposure are mottled and blotchy.

The browning develops suddenly on leaves directly exposed, first as a soft almost parboiled brown before becoming dry and brittle.

Control and Management

Step one is to simply relocate your plant to a shadier spot. Avoid southern-facing windows and those without any coverings or curtains.

It’s worth being mindful too those light levels change as the season pass, so a gentle indirect light in the winter may be a burning blaze come summer.

Be sure to keep an eye on those sunbeams crossing your rooms as the season changes.

As for the leaves, just like you or I the sunburn is largely cosmetic. If the leaf is not badly afflicted, it will still photosynthesize and provide your plant with food. But if it is browner than green it’s best to trim and move on.

Nutrient Deficiency

Your indoor begonia needs to be regularly fertilized through the growing season. Without a regular supply of nutrients, your plant is unable to build the strong, gorgeous leaves that begonias are known for.

Brown leaves that are fragile, on stems prone to snapping, maybe a sign you need to feed your begonia.

Control and Management

Start by fertilizing your begonia. A standard liquid fertilizer with a 3-1-2 ratio of nitrogen, phosphorus, and potassium is ideal for most varieties. During the spring and summer, you can add this sort of booster to your watering regime.

It may also be prudent to make sure your potting medium has enough organic matter distributed evenly throughout.

Peat moss and coir decay gradually, releasing a perfect measure of nutrition as your plant grows.

A mix with too much plain soil or inorganic additives such as vermiculite or perlite will not provide that slow, reliable support.

Fertilizer Burn

On the other hand, too much fertilizer brings its own problems. Nitrogen is potent and can scald the delicate roots of your begonia.

If your browning beauty has salts developing on the surface of its growing medium it’s likely there is damage below the surface, too.

Strongly colored runoff after watering that smells of your preferred fertilizer is another sign there’s too much left in the medium between treatments.

Control and Management

To correct this issue, you will need to clear the pot of excess fertilizer.

  1. Remove any visible crystals from the surface of your growing medium.
  2. Place your pot in a shower or sink.
  3. Fill your pot with running water, allowing it to flow through the medium and out your drainage holes. This dissolved the remaining fertilizer and washes it away.
  4. Flush your pot for at least five minutes.
  5. Allow your pot to drain for at least half an hour before returning it to its tray or saucer.

Refrain from fertilizing your begonia until the leaf browning clears.

Insect Infestation

I personally find that nothing is more annoying than an infestation of pests. Mealybugs, spider mites, thrips, and scales all love to have a good nibble at your poor begonias.

If your browning is irregular and spotty and extends to stems and new growth, it’s likely that pests are harrying your poor darling.

Have a look at the crevasses around the base of leaves and stems. Pay attention to any little nook and crannies that a pest could occupy.

Thrips and mealybugs can be very hard to spot, and present as little flecks of dark color or fluff. Spider mites are no larger than a pinhead, but leave webbing on your plant.

Keep an eye out for ants, too. While ants will not attack your begonia, mealybugs and scale bugs secrete a sweet liquid called “honeydew” that ants love. I’ve often spotted the ants before the pests.

Control and Management

For small infestations, remove the pests munching your begonias by hand. Wipe the little criminals from the leaves with a dab of rubbing alcohol on a cotton tip.

I like to rinse them off with a gentle spray under a shower head or garden hose, though it’s best to reserve this for warm weather when the leaves can dry thoroughly before returning your plant to its spot.

For more severe infestations, it’s best to break out the insecticides. Neem oil is a reliable option and a firm favorite, but any insecticidal soap should do the trick. Be sure to apply every 5-8 days, as eggs can hatch and catch you unawares.

It’s also important to quarantine the infested plants during this process, to prevent the little criminals from jumping ship and getting stuck into the rest of your plants.

Disease

Begonias are more prone to disease than other indoor plants, especially fungal infections. Below are the selection most likely to attack your begonia.

Bacterial leaf spot

Caused by the Xanthomonas campestris pv. Begoniae bacteria, this browning appears in patches that are waterlogged and ringed in yellow. The leaves will individually drop off as the disease progresses.

Botrytis Blight

If your leaves turn a tannish brown, and the crown of your begonia rots away, you may have a case of Botrytis cinerea or Botrytis Blight.

Pythium Stem Rot

Brown leaves preceded by rotting stems and petioles are possible signs of a Pythium infection. This malignant fungus attacks the whole plant, root to tip.

Control and Management

Septoria Leaf spot

If your browning began as speckled leaves that pale and crisp, you may be suffering an infection of Septoria lycopersici. This fungus loves damp, cool conditions, and will tear through your collection if left untreated.

Rhizoctonia Crown Rot

This killer takes your begonia out from the top down, attacking the crown first. Stems are also afflicted, causing leaves to brown before killing your poor plant entirely.

Powdery Mildew

Leaves that first turn a silvery or powdery white before browning are likely to be suffering from a powdery mildew infection caused by the Oidium mold. It thrives in damp, poorly ventilated conditions.

Control and Management

The first step for any diseased plant is quarantine. Get your infected begonia safely away from any other indoor plants to prevent your infection from spreading.

For mild infections, it’s often enough to trim away diseased leaves and dispose of them in household garbage. Always sterilize your scissors or shears afterward to prevent cross-contamination.

But if your infection is well established, it may be an idea to apply an all-purpose plant disease treatment.

As many symptoms of begonia diseases overlap, it’s a good idea to use something that is both antibacterial and fungicidal to ensure you are truly treating your plant’s affliction. It will also prevent your begonia from succumbing to any secondary infections.

If you see no response to treatment after two weeks, sadly it may be time to say goodbye. Some plant diseases, especially Pythium, are resistant to treatment, and disposing of your plant is the only way to prevent it from spreading.

Just toss the lot, pot, and all. Infected soil and pots should not be re-used. I always believe that prevention is better than cure. Begonias are especially vulnerable to fungal diseases.

They love damp, stagnant air, so always keep your begonias well ventilated. Never wet your begonia’s leaves when watering and avoid misting the leaves. Always make sure the leaves are dry after cleaning or removing pests.

Edema

Keep an eye out for welts, blisters, or galls on the leaves and stems of your begonia. This is edema.

Your plant is drawing too much moisture from the soil, causing it to build up in the tissue of the plant.

If untreated, it can lead to browning of the leaves. While its primary cause is too much water, too much fertilizer and too much humidity contribute.

Control and Management

Make sure your begonia is fertilized and watered less frequently and appropriately for the season and it should clear.

It may also be worth ensuring your potting medium is well-draining, to prevent too much moisture from becoming available to your plant as well.

Frost Damage

Your begonia is a tropical plant. They cannot abide by the cold and are not frost tolerant. If your brown leaves have developed after a cold spell, especially in plants close to windows or in drafty areas, frost may be your culprit.

Look for browning that quickly becomes soggy. This is evidencing your leaf has frozen and thawed, killing the cells altogether.

Control and Management

Always keep your begonia away from windows during the winter months. While it may be tempting to place them in a brightly lit window to warm them up, you will in the end do more harm than good.

Also, be wary of drafts. Find a consistently warm part of your home for your darling to overwinter.

Low humidity

Begonias thrive in a humid environment, preferring humidity of around 40% and above. Without a bit of moisture in the air, your begonia will dry out and become crisp. Eventually, your leaves will begin to brown.

It can be tricky to manage humidity for houseplants. Climate control, aggressive air conditioning, draws moisture from the air, and will dry your begonia out. Then it’s quite difficult to hit that 40%!

Low humidity is often the culprit for browning leaves in otherwise healthy, well-tended plants. If you’ve tried everything above and still have brown leaves, this is probably your issue.

Control and Management

Increasing local humidity is often your best bet when your indoor plants are suffering. It’s much easier to raise the humidity in one area of your growing environment than it is to turn an entire home or office into a humid tropical garden.

To increase local humidity:

  • Use a pebble tray. Place a layer of flat stones or pebbles in a shallow tray. Fill it to halfway up the height of the stones with clean water, then rest your pot on top. This allows the water to evaporate gradually, providing an area of local humidity.
  • Cluster humidity-loving plants together. As plants grow, they release moisture via transpiration. When clustered together, your plants will create a micro-climate ideal for maintaining atmospheric moisture.
  • Consider using a small, electric humidifier. They are often quite affordable to purchase and run and will provide reliable, consistent humidity.

How to Prevent Brown Leaves on Begonia

The dramatic, captivating leaves of your indoor begonia will provide a real pop of flair to your collection. Keep those leaves in good condition by doing the following:

  • Water only when the top inch of medium is dry.
  • Water to the base of the plant, away from leaves.
  • Ensure your begonia is in a well-draining, soil-free medium.
  • Give your begonia medium to low indirect sunlight.
  • Place your begonia away from direct sun and cold windows.
  • Fertilize only once a month during the spring and the summer months.

Follow these tips and your indoor begonia will provide you with plenty of flashy, charming foliage to enjoy.

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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