Plant care guide
Begonia Leaves Curling? Check Water, Humidity, and Roots
Updated · First published
Why are my Begonia leaves curling?
Curling begonia leaves usually point to water stress. That can mean a pot that has dried out, or roots damaged by wet mix that can no longer supply the leaves. Cold, salts, pests and powdery mildew are the other things to rule out.
What to do first
Feel the mix before you do anything. Water a dry, light pot from below. If the mix is wet, stop watering and check the roots. Then look under the leaves for pests or white powder, and move the plant away from cold windows and heat vents.
Curled begonia leaves are a sign the plant is under stress, but curling alone does not name the cause. Two opposite problems look alike: too little water and too much. Feel the mix before you water, because the wrong fix makes things worse.
Virginia Cooperative Extension’s watering guide lists leaves curling upward or downward as a symptom of underwatering. Iowa State University Extension’s guide to environmental problems explains why wet mix can look similar. Roots in mix that stays wet rot and die, and with fewer roots the plant cannot take up enough water.
Match the curl to the clues
| What goes with the curl | Check first |
|---|---|
| Dry, light pot; mix shrunk from the edge; brittle or brown edges | Underwatering |
| Wet, heavy mix; yellowing; soft stems; sour smell | Overwatering, root rot |
| Curling or damage after a cold night by a window or a draught | Cold |
| White crust on the mix or rim, recent feeding | Fertilizer salts |
| Insects, webbing or sticky residue under the leaves | Pests |
| White powdery spots on the leaves | Powdery mildew |
Before you worry, check the leaf shape. NC State Extension’s begonia profile notes that begonia leaves are usually asymmetrical, at least at the base. Uneven, lopsided leaves are normal.
If the pot is dry
- Water until the whole root ball is wet. Virginia Cooperative Extension recommends bottom watering for begonias, because they do not tolerate wet foliage.
- If the mix has shrunk from the pot, rewet it slowly. The same guide says bottom watering is also the best way to rehydrate dry mix. The saucer may need refilling several times.
- Do not leave the pot standing in water for more than 60 minutes.
- Check the mix more often from now on. UConn’s Rex begonia factsheet suggests watering when the top 2.5 cm (1 in) feels dry. It adds that slight underwatering is better than overwatering.
Virginia Cooperative Extension notes that a wilted plant that perks up after watering has enough water in the root zone. Crisp tissue will not recover.
If the mix is wet
- Stop watering and empty any saucer or outer pot.
- Slide the plant out and look at the roots. University of Maryland Extension’s root rot page describes rotted roots as brown to black and soft or mushy. Plants with root rot can wilt even when the mix is moist.
- If the roots are rotting, follow our begonia root rot guide.
NC State warns that begonias are highly susceptible to root rot. UC IPM’s begonia disease table notes that Pythium root rot is favoured by excess water.
If the mix is fine
Cold. NC State says begonias do not tolerate temperatures below 13 °C (55 °F). Move the plant away from cold glass and outside doors. Iowa State also warns against heat vents and against trapping plants between a window and a curtain.
Dry air. Iowa State calls low humidity the most common cause of brown leaf tips. Its humidity FAQ suggests a humidifier, grouping plants or a pebble tray. It notes that misting does not work well.
Salts. Iowa State says excess fertilizer salts can brown leaf edges. Flush the pot with plain water, let it drain, and feed less. UConn suggests quarter-strength fertilizer every 2–3 weeks in the growing season, with none from October until spring.
Pests. NC State lists mealybugs, whiteflies, thrips, scales and spider mites on begonias. Check leaf undersides and the growing tip with a hand lens. Identify what you find before you buy a treatment.
Powdery mildew. UC IPM describes white, powdery spots on both leaf surfaces and recommends more air movement. NC State advises watering at the base and keeping water off the leaves. Our powdery mildew guide covers treatment.
Watch the new growth
Once you have fixed the cause, keep conditions steady. Changing several things at once makes it hard to see what helped. New leaves that open flat show the plant has recovered.
If edges are turning brown as well as curling, see our crispy begonia leaves guide. The begonia types guide explains how care differs between groups.
References
- Virginia Cooperative Extension: Properly Watering Container Houseplants (SPES-804)
- Iowa State University Extension: Diagnosing Houseplant Problems from Improper Environmental Conditions
- NC State Extension Gardener Plant Toolbox: Begonia
- UC IPM: Begonia diseases (Floriculture and Ornamental Nurseries)
- University of Maryland Extension: Root Rots of Indoor Plants
- UConn Home & Garden Education Center: Rex Begonia
- Iowa State University Extension: How can I raise the relative humidity indoors for my houseplants?
How this guide was put together: Virginia Cooperative Extension, Iowa State University Extension, NC State Extension, UC IPM, University of Maryland Extension and UConn Home & Garden Education Center guidance.