The sick Calathea can react with brown spots on the tip, on the edges or in the middle of the leaves, and ultimately, the plant dries in entire leaves with a brown shade.
Poor health with a brown spot in Calathea is a tell-tell sign that you have messed up with its care requirements.
There’s nothing to be panicked about as it is fixable, but you definitely need to be alarmed.
Table of Contents Show
How to Treat Calathea Brown Spots? (Causes & Solutions)
Calathea plants boast striking patterned green leaves with silver brushmarks on the top and a burgundy-purple underside.
However, if they experience poor care, you can not stop them from turning you with rusted or brown spots on the leaves.
Let us explore more about this issue and find ways to treat them.
1. Use of Harsh Water
Using improper water, especially those higher in salts, chlorine, and fluorine can poison your Calathea.
These minerals hinder the nutrition absorption rate, which directly hampers the photosynthesis process causing wilting, drooping, and browning of leaves.
- Immediately replace the harsh water with either distilled, rainwater or soft water.
- Plunge the pot in tepid water to flush off accumulated salts and other minerals.
- Take a mineral test of water and install a filtration system.
2. Drought Condition
In the natural habitat, Calathea grows under the canopy, where the soil remains consistently moist.
So, missing to water Calathea for more than two sessions causes moisture stress, which causes brown and dry leaves.
Depriving the soil of moisture disrupts the whole photosynthesis and other physiological functioning, causing dry, dull, and brown spots.
So, if you spot Clathea brown leaves along with dry, cracked, and lighter soil base, water it as soon as you notice it, as it desperately needs water.
- Prune off excessively browned leaves to prevent energy loss through them and channel energy towards healthier growth.
- Submerge your Calathea pot under a pool of tepid water until the topsoil is completely saturated with water. Follow the bottom watering process until the plant rejuvenates.
- Alternatively, follow a watering schedule with a preferable schedule of watering it once or twice a week in summer and twice or thrice a month during winter.
- Immediately water the plant if the top 25% of the soil is dry.
- If the soil is extremely dry and pulled away from the pot, push it towards the pot’s surface while watering to prevent water seepage from the corner.
3. Excess Watering
Unlike underwatering, overwatering can be detrimental to your Calathea.
If the leaves of your Calathea appear tender and water soaked with brown spots, it is drenched in water.
- Get rid off the leaves that are excessively spotted.
- Avoid watering the plant for a couple of days until the soil dries completely.
- If the plant is severely affected, take it off the pot and check its roots.
- Immediately discard such roots, then apply fungicides before repotting them on dry soil if you find dark brown and tender roots with a rotting smell.
- To prevent overwatering, water the plant only after the top soil is dry and drip off excess water.
4. Scorching Sunlight
Do you think your Calathea likes to sunbathe like humans all day long? Absolutely no.
In their native environment, they grow under the shade of tall trees. If not, scorching sunlight causes excessive water loss from plants’ leaves, which turn dry with brown leaf tips.
As the upper leaves’ shade protects lower leaves from direct sun, the lower leaves are generally unaffected.
- Cover your plant with a light curtain or drape if it experiences direct sunlight from the window.
- Place your Calathea within 1-3 feet from the eastern-facing window, where it receives 6-8 hours of indirect light with 1-2 hours of a morning sunbeam.
- While placing it at the south-facing window, keep it at least 3 feet away.
- Clip off excessively brown leaves to save the plant’s energy.
Unlike summer, it is better to provide it with 2-3 hours of mild winter sunlight. So, move it to a warmer location where it can receive warmer light and thrive well during its dormancy.
5. Temperature Stress
The ideal temperature range for Calathea is anything that hovers between 65-80°F.
Similarly, cold stress caused by a temperature drop to 55°F or low results in water freezing in the cell. This severe condition causes cell bursts disrupting overall physiological activities, whose sign is brown spots in leaves.
- House your outdoors Calathea indoors as the night temperature starts dropping below 65°F.
- Place the plant on a heating pad or insulate it with a frost blanket.
- Increase humidity around the plant as moisture helps to compensate for water loss caused by excessively high temperatures.
- As a preventive measure, you can place mulch such as straw or dried grass on top of the soil to prevent temperature loss from the soil.
- If your Calathea is near a heating or cooling vent, immediately move it at some distance off to prevent extreme temperatures.
- Never leave your Calathea near a window on a frosty night, as the temperature fluctuation between night and day is high there.
6. Low Humidity
Calathea enjoys higher humidity that ranges between 60-80% as it is a tropical plant. Keeping it at low humidity causes its leaves water to evaporate rapidly, which damages the cell membrane causing dark brown spots.
Although some Calathea can thrive within 50% of the humidity, Calathea Orbifolia strictly needs humidity higher than 60%.
- The most effective way to solve the low humidity problem in Calathea is installing a plant humidifier.
- Next, you can mist your Calathea in the morning to keep its leaves moist.
- Grouping your houseplants together is also an effective method. However, the technique might be dreadful if any one of your plants is disease and pest infested.
- Placing your Calathea in a well-ventilated kitchen or bathroom also boots humidity.
- You can place a wet pebble tray under your Calathea plant as the evaporate after the tray helps to lock moisture in the air.
7. Use of Wrong Potting Mixture
If the soil does not hold water, it causes draught causing dry brown leaves.
Similarly, it burns Calathes’s roots and leaves if the soil is highly alkaline.
- Replace your potting mix with a potting mix that is lighter, porous, humus, slightly acidic soil that holds optimum water while dripping off the excess water.
- Avoid using cacti and succulent mix and pure garden soil.
8. Fertilizer Burn
Do you feed your Calathea even during winter or provide them with highly concentrated fertilizers? If so, why would your Calathea not have brown spots?
Calathea needs a consistent supply of diluted nutrition once every month, excluding falls. Overfertilizing Calathea leads to excessive salt in the soil, which burns tender roots and leaves.
Besides, the accumulation of salts makes the soil alkaline, which is unfit for the healthy growth of your Calathea.
- Wash off excess fertilizer and accumulated salts by submerging the pot in a shallow container with tepid water for 15-20 minutes.
- Always dilute the fertilizer to 1/4th of its strength or as level instructed in the pack before applying.
- Let your Calathea rest during winter by avoiding fertilization.
Though Calathea is non-toxic to cat, keep your pet away while fertilizing the plant.
9. Pests and Diseases
Pests, including mealy bugs, spider mites, and aphids, are responsible for Calathea brown spots.
Similarly, plant diseases such as Alternaria leaf spot, Helminthosporium leaf spot, grey mold, and fusarium root rot cause different kinds of brown spots in Calathea leaves.
- To avoid further spread and redirect the plant’s energy on growth and developing immunity, chop off all the infected parts.
- Immediately isolate your plant from other healthy plants.
- Spray Neem oil or commercial horticultural oil over the plant to effectively treat them.
- Dip a cotton ball on 75% diluted isopropyl alcohol and dab it along the pest-infected parts.
- To treat disease-causing leaf spots, immediately spray fungicides on the affected parts.
- To get rid of grey mold, apply a fungicide containing chlorothalonil.
If you wish to decorate your home with Calatheas, choose one of Calathea varieties.
Calathea leaves can have brown spots if their older leaves are in the process of degeneration. Any other cause for brown spots on Calathea needs immediate attention as it symbolizes certain care deficiencies.
Sometimes Calathea leaves might turn brown even with the best care. In that condition, let the plant rest, and it shall take care of itself.