How to Care For Rex Begonias

rex begonia care

Rex Begonias can be fussier with watering and humidity levels compared to what would be considered beginner houseplants. Once you have your watering routine down and know your plant lives in a humid enough room, they are easy to care for and add the color to your home you want.


Common NameRex Begonia, Begonia Rex, King Begonia, Painted-leaf Begonia.
Scientific NameBegonia rex 
OriginThe wild species is native to rocky forests in Vietnam, Myanmar, and the eastern Himalayas. It was named the plant after Michel Begon, a fellow botanist.
GrowthBegonia rex grows as a short perennial shrub. They reach up to 12–18 in. tall and wide.
Ease of CareThey are suitable for plant owners with some experience because begonias can be sensitive to overwatering.
SoilThey need well-draining soil with additions like sand, peat, and bark. A slightly acidic pH balance between 5.7–6.2 is best.
Light RequirementsInside: They grow best with moderate to bright, indirect light. Outside: Keep them in 4–6 hours of partial sun and sheltered from the wind.
Watering NeedsWater them thoroughly until draining, then wait until the first 2 in (5 cm) become dry.
TemperatureThey prefer 60–75 °F (16–24 °C)
HumidityThey survive in 50%+ humidity, which is typical household humidity.
USDA HardinessOutside, they will grow in zone 10–12.
PottingRepot in the spring whenever roots push out the drainage holes or above the soil. Use a pot size that’s another 1–2 in (2.5–5 cm) wider in diameter than the previous pot.
FertilizerYou fertilize begonias while watering with a balanced formula diluted to ½ once a month, or ¼ once every two weeks in the spring and summer.
PropagatingYou propagate Rex Begonias by stem cuttings, leaf cuttings, and division.
Care ProblemsAvoid overwatering. The signs include wilting leaves, yellowing leaves, and dark and mushy stems. Also, avoid low humidity, which leads to infestations.
PestsCommon pests include scales, mealybugs, and thrips. Wipe them off with diluted soap or neem oil.
ToxicityBegonia Rex rhizomes and oils can be toxic to humans and animals, irritating the skin and causing problems for the stomach and kidneys.


Rex Begonias love peat-based soil mixes because of the higher acid concentration. The ideal pH falls into the 5.7–6.2 range. Bark components also help with raising the acid levels. Their sensitivity to overwatering also makes better drainage a good idea. Drainage components include perlite or vermiculite mixed in or small pebbles at the bottom.


The Begonia Rex prefers 4–6 hours of bright indirect light. Depending on the variety, it may need less light based on how much deep green it has. Darker green plants generally tolerate less sun because they have extra chlorophyll to compensate. Whereas pale and colorful varieties need more help with their photosynthesis.


Rex Begonias can be prone to root rot when they’re overwatered regularly. One common rule for watering is to wait for the first several inches of the soil to dry out before watering again. This rule is essential for begonias.


The Begonia Rex thrives in temperatures between 65–75° F (18–24° C). Below 60° F (16° C), they get stressed and lose leaves. Even indoors, begonias need to be kept away from cold windows and drafts, including heaters and AC vents.

They also grow in USDA Hardiness Zones 10–12 if you want to keep your plant outside during parts of the year.


Rex Begonias need humidity above 50%. Most households have this moisture, but if you live somewhere drier, you can keep the plant in a bathroom or near the sink in the kitchen. You can also create humidity by misting, using a humidifier, or adding a pebble tray.


Rex Begonias take around 1–2 years of growth before needing to be repotted. What’s important is that you look for the cues like roots trying to escape through the pot’s drainage holes or reaching above the soil. Otherwise, they enjoy a snug fit.


During the spring and summer, Rex Begonias benefit from fertilizer diluted to ½ every month or ¼ every two weeks. Adding fertilizer during the main growing seasons helps the plant to absorb it properly and not have the chemicals sit on the roots and burn them.


The easiest propagation method for Rex Begonias is rhizome division. As long as a divided section has a few leaves attached to it, you can pot that section and start a new individual. Stem cuttings take more time and effort, but they will grow fresh roots if they have enough time in a jar at a sunny window.


Like many houseplants, the Begonia Rex can get any of the common sapsuckers: 

  • Scales
  • Mealybugs
  • Thrips

If you see any insects on your plant, particularly under leaves, wipe some neem oil or diluted dish soap on them.


If you have an unbalanced watering routine or humidity levels, your plants may suffer from the following:

  • Root rot: It looks black and mushy on the lower stem and comes from frequent overwatering. 
  • Powdery mildew: It causes white mold to grow on the undersides of stems and leaves. 
  • Gray mold: comes from low humidity and creates dark patches on the leaves.


Rex Begonias are also toxic to humans and household pets. It causes gastrointestinal and kidney problems when eaten, especially if the portion is the rhizome. Also, the sap can cause skin irritation if you don’t wear gloves.

Other Care Points

Rex Begonias don’t need much extra care. Beyond getting their watering right, they are easy to please. Sometimes you may want to prune leggy stems with sterilized scissors so your plant can have a bushier appearance or dead leaves. 

Pruning is most beneficial in the fall as the plant adjusts to lower light levels and does better with less body to maintain. This approach improves the plant’s growth next spring.


The greatest challenge to Rex Begonia is picking which ones to get. Considering that most of them share similar colors, they all find unique ways to express their colors. Even varying how much light you allow your plant can change the colors, so you can experiment with how strong or subtle you want the colors.

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