Quick answer: Small, humidity-loving begonias like B. prismatocarpa, B. thelmae, B. foliosa, B. rajah and mini rex hybrids do well in closed terrariums and vivariums. Give them airy soil, 70–90% humidity, gentle airflow and medium-bright LED light. Keep the stems out of standing water. Rot and powdery mildew are the main threats.
Why begonias are worth the effort
There are more than 2,000 begonia species, and some of the most beautiful are tiny forest-floor plants from Southeast Asia and South America. They grow in permanently humid ravines and on mossy rocks. Many of them actually grow better in a terrarium than on a windowsill, because household air is too dry. For the plant-focused keeper they bring metallic sheens, spots, spirals and deep reds that few other terrarium plants can match.
Best begonias for terrariums and vivariums
| Species | Size | Look | Notes |
|---|---|---|---|
| Begonia prismatocarpa | 5–10 cm | Small green leaves, bright yellow flowers | Flowers almost constantly in humid terrariums. Very beginner-friendly |
| Begonia thelmae | Creeping | Tiny round leaves, sometimes spotted | Trails over moss and cork. Great ground cover |
| Begonia foliosa (fern-leaf begonia) | 15–30 cm | Tiny leaves on arching stems | Delicate, airy texture |
| Begonia rajah | 10–20 cm | Puckered bronze-red leaves | Needs consistently high humidity |
| Begonia amphioxus | 15–25 cm | Narrow leaves with red spots | Striking, but more demanding |
| Mini rex hybrids | 10–20 cm | Silver, pink, purple patterns | Easy to find in Canadian garden centres; choose small ones |
| Begonia 'Lithuania', 'Ninja', 'Spotted Cherry' | Varies | Varied hybrids | Hobby-grower varieties suited to terrariums |
Avoid large cane begonias, the "Angel Wing" types, and big rex plants. They outgrow most enclosures quickly.
Where to place begonias in your build
Most terrarium begonias are foreground and midground plants that like shelter. Tuck them:
- at the base of a cork round or under an overhanging cork flat;
- on mossy ledges of a cork background, in a pocket of soil and sphagnum;
- against stone, such as Seiryu stone or feather rock, where creepers like B. thelmae will spread across damp surfaces.
Soil and planting
Begonias have very fine roots and short, succulent stems that rot easily. Plant them in an open, airy substrate like Jurassic ABG Terrarium Mix, which Jurassic Reptile Products makes in Canada, over clay balls for drainage. A slight mound under each plant helps water move away from the stem. Don't bury the crown.
Many collectors grow small begonias directly on a bed of live moss or sphagnum laid over the soil. The moss keeps roots moist without waterlogging them.
Humidity and airflow
Begonias want high humidity, but stagnant air invites powdery mildew and botrytis (grey mould). The ideal is humid air that moves gently:
- Aim for 70–90% humidity.
- Use a top vent, a front vent, or a small USB fan on low to create slow circulation.
- Avoid leaving water droplets sitting on leaves overnight. Mist in the morning so leaves dry during the light period.
- In closed jars, open the lid briefly once a week if condensation never clears.
Light
Medium, indirect light is ideal. Under 6,500K LEDs, place begonias in the middle and lower parts of the enclosure. Too much light bleaches and crisps the leaves, and dark-leaved species lose their colour. Too little light makes them stretch. Rex hybrids in particular show their best colour under moderate, steady light rather than intense light.
Watering and feeding
Keep the soil lightly and evenly moist. In a bioactive system, nutrients from breaking-down leaf litter and waste usually feed begonias well. If an older, plant-only terrarium looks pale, a very diluted organic feed like ABG Pure Organics Natural Fertilizer can help. See our fertilising guide.
Propagation
Begonias propagate easily from stem cuttings, and many from single leaves. Lay a rex begonia leaf flat on moist sphagnum, nick the main veins with a clean blade and pin it down. New plantlets often emerge from the cuts within weeks in a humid container. Creeping species like B. thelmae root along their stems wherever they touch moss.
Problems and fixes
| Problem | Cause | Fix |
|---|---|---|
| White powder on leaves | Powdery mildew | Remove affected leaves, increase airflow, avoid misting at night |
| Grey fuzz, collapsing stems | Botrytis or rot | Cut out affected tissue; take cuttings; reduce soil moisture |
| Crispy leaf edges | Low humidity or too much light | Close vents partly; move the plant lower |
| Leggy, sparse growth | Low light | Increase light; pinch tips |
FAQ
Are begonias safe for dart frogs and geckos?
Begonias contain oxalates. They are used in many dart frog and small gecko vivariums without issue because those animals don't eat plants. Leave them out of builds with herbivorous or omnivorous reptiles.
Can I use a grocery store rex begonia in a terrarium?
Yes, if it's small, but expect it to grow. Rinse off the potting soil and check for pests first.
Why do my begonias melt in a closed jar?
Usually the soil is too wet and there's no air exchange. Use less water, add a drainage layer and vent occasionally.