Begonia Growing Guide
Begonia spp.
The right care for a begonia depends heavily on which type you have — wax, tuberous, or rex — and mixing up their needs is the most common way to lose one.
Light
Bright, indirect light; shade to part sun outdoors
Soil
Rich, well-drained, slightly acidic potting mix
Water
Let the top inch dry between waterings; avoid wetting leaves
Hardiness
Grown as annual/houseplant in most of Canada
Mature size
6 in–2 ft depending on type
Bloom time
Summer through fall (flowering types)
Begonias cover a huge range of plants — the compact wax begonias sold as shade-bed annuals, the showy tuberous begonias grown for their large blooms, and rex begonias grown mainly for dramatic foliage. All three want similar general conditions (bright indirect light, well-drained soil, water at the base), but their bloom habits and winter care differ.
Planting
- Plant wax begonias outdoors after frost risk has passed, in part shade to full shade
- Start tuberous begonias indoors 8–10 weeks before last frost, tubers hollow-side up, barely covered
- Use a rich, well-drained potting mix — begonias dislike heavy, waterlogged soil
- Space plants 8–12 inches apart for airflow, which reduces the fungal issues begonias are prone to
Watering & humidity
- Let the top inch of soil dry before watering again — begonias are more often killed by overwatering than drought
- Water at the base or use bottom-watering for potted plants; wet foliage invites powdery mildew and botrytis
- Indoor begonias appreciate higher humidity, but avoid misting leaves directly — use a pebble tray instead
- Reduce watering in cooler months when growth naturally slows
Feeding
- Feed flowering types every 2–4 weeks with a balanced fertilizer during active growth
- Use a fertilizer slightly higher in phosphorus to encourage blooms on tuberous types
- Rex begonias (grown for foliage, not flowers) need less frequent feeding — every 4–6 weeks is enough
- Stop feeding in fall as growth slows for winter
Overwintering tuberous begonias
- After the first light frost blackens the foliage, dig up tubers and let them air-dry for a few days
- Store tubers in dry peat moss or vermiculite in a cool (45–55°F), dark, frost-free location
- Check periodically through winter and discard any tubers showing rot
- Restart indoors 8–10 weeks before the next season's last frost
Common problems
- Powdery mildew (white powdery coating): improve air circulation, water at the base, avoid overcrowding
- Stem or root rot: almost always overwatering or poor drainage — let soil dry more between waterings
- Leggy, stretched growth: insufficient light — move to a brighter spot
- No blooms on tuberous types: often insufficient light or a fertilizer too high in nitrogen relative to phosphorus
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Frequently asked questions
Let the top inch of soil dry out between waterings. Begonias are far more commonly killed by overwatering and root rot than by underwatering.
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