Rex begonia, also commonly known as painted-leaf begonia or fancy-leaf begonia, is a semi-tropical perennial plant known for its large variegated leaves that are brightly colored in shades of green, red, silver, and even purple. Rex begonia is typically grown as an outdoor container plant or houseplant. It can be challenging to find just the right conditions for Rex begonia to display its best leaf color. Light is not usually the issue but temperature is key. Ideal daytime temperatures for this plant to thrive hover around 70 degrees Fahrenheit, nighttime temperatures around 60 degrees, and indoors, a constant humidity level around 50 percent would suffice. Note that rex begonia is toxic to animals.