Plant care guide
Rex Begonia Crispy Leaves: Diagnose and Stop the Damage
Updated · First published
Why are my Begonia rex leaves crispy?
Crispy edges on a Rex begonia most often mean dry air, a pot left too dry, or direct sun. Fertilizer salts and root rot can produce similar damage, and powdery mildew or leaf spot can look like it at first glance.
What to do first
Check the top 2.5 cm (1 in) of mix, the window the plant faces, and the leaf surfaces. Water a dry pot from below, move the plant out of direct sun, and raise the humidity around it without wetting the leaves.
Crispy, papery edges on a Rex begonia are upsetting, because the leaves are the reason you grow it. The brown tissue will not turn green again. What you can do is find the cause and protect the next leaves. A few checks narrow it down.
Rex begonias are fussier than most houseplants. The UConn Home & Garden Education Center’s Rex begonia factsheet calls them “a bit demanding to grow”. It says brown leaf tips are typically a sign of low humidity. NC State Extension’s begonia profile goes further: Rex begonias need humidity above 75% and decline if it is too low.
Match the damage to the cause
| What you see | Check first |
|---|---|
| Brown, crisp edges on many leaves, winter heating on | Dry air |
| Crisp, curled leaves, light pot, mix pulled from the pot edge | Pot dried out |
| Bleached or brown patches on the side facing a window | Direct sun |
| Brown edges plus white crust on the mix or pot rim | Fertilizer salts |
| Wilting or yellowing in wet mix, soft stems | Root rot |
| White powdery spots, or small water-soaked spots that turn brown | Leaf disease |
Dry air. Iowa State University Extension’s guide to environmental problems names low humidity as the most common reason for brown leaf tips. Homes are often driest in winter.
Dry pot. Iowa State also lists inconsistent watering, especially letting plants dry out too long. Virginia Cooperative Extension’s watering guide adds dry or brittle leaves, curling, mix shrinking from the pot, and a very light pot.
Direct sun. UConn advises bright but indirect light. In a south or west window, set the plant a few feet back so the leaves are out of direct sun. Iowa State notes that scorch often follows a sudden move into brighter light.
Salts. Iowa State links excess fertilizer salts to brown leaf edges.
Root rot. UConn warns that too much water invites root rot. UC IPM’s begonia disease table describes Pythium root and stem rot: small, discoloured roots and water-soaked stems that collapse.
Leaf disease. UC IPM describes powdery mildew as white, powdery spots on both leaf surfaces. Bacterial leaf spot starts as small, water-soaked, blister-like spots that turn brown.
What to do
If the air is dry:
- Put a hygrometer near the plant. UNH Extension’s humidity guide recommends pairing one with a humidifier.
- Run a humidifier close to the plant. UNH says this gives the most consistent control.
- Move the pot away from heat vents, radiators and outside doors.
- Group plants or use a pebble tray, with the pot above the water line, as UConn suggests. A terrarium also works for small plants. UNH advises lifting the lid now and then.
Skip misting. Iowa State’s humidity FAQ says it is not effective. UConn warns that wet leaves make Rex begonias more prone to powdery mildew.
If the pot is dry:
- Water thoroughly. Virginia Cooperative Extension recommends bottom watering for begonias, because they do not tolerate wet foliage.
- Do not leave the pot standing in water for more than 60 minutes.
- From then on, water when the top 2.5 cm (1 in) of mix feels dry, as UConn advises.
If the mix is wet or the stems are soft:
- Stop watering and check the roots. See our begonia root rot guide.
- Repot into a shallow, wide pot with light, well-draining mix. UConn suggests a soilless mix like those made for African violets.
If you see salt crust:
Flush the pot with plain water and let it drain. UConn recommends quarter-strength fertilizer every 2–3 weeks in the growing season, and none from October until spring growth starts.
If you see powder or spreading spots:
Keep the leaves dry, space plants out and remove badly affected leaves. Our begonia powdery mildew guide covers treatment.
Judge the fix by new leaves
Trim fully dead leaves at the stem. Iowa State notes that trimming brown edges only helps temporarily if the cause remains.
In winter, slow growth is normal. UConn notes that Rex begonias may go dormant in low light and drop leaves. Growth slows below 16 °C (60 °F). Water less until new growth appears in spring.
See the Begonia types guide for how Rex care differs. Once the plant is stable, you can propagate it from leaf cuttings.
References
- UConn Home & Garden Education Center: Rex Begonia
- NC State Extension Gardener Plant Toolbox: Begonia
- UNH Extension: How can I increase the humidity indoors for my houseplants?
- Iowa State University Extension: Diagnosing Houseplant Problems from Improper Environmental Conditions
- Iowa State University Extension: How can I raise the relative humidity indoors for my houseplants?
- Virginia Cooperative Extension: Properly Watering Container Houseplants (SPES-804)
- UC IPM: Begonia diseases (Floriculture and Ornamental Nurseries)
How this guide was put together: UConn Home & Garden Education Center, NC State Extension, UNH Extension, Iowa State University Extension, Virginia Cooperative Extension and UC IPM guidance.