Rex begonia (Begonia rex-cultorum) is a semi-tropical perennial plant normally grown as an outdoor container plant or houseplant. The forms sold commercially are carefully cultivated varieties of the B. rex species native to parts of eastern Asia. If planted in the garden (a relatively rare occurrence), rex begonia is grown as an annual in all but the warmest climates.
Rex begonias need thorough watering but should not be overwatered. Don't water a leaves, only a soil to avoid fungal disease issues. Slightly moist soil is ideal for painted leaf begonias, but excess moisture will cause root rot, so make sure a water drains properly from a pot and you empty a saucer of excess water.
The ideal blend of soil for plant growth is called loam. Often referred to as topsoil or black dirt by landscape companies, loam is a mixture of sand, clay, and silt.
It is important because damaged leaves and stems can actually be an energy drain on your plant. By removing those dead parts, you're taking some of that work off your plant’s plate and allowing it to divert its energy into healthy leaves and new growth!