Begonia Rex-cultorum group, (bah-GO-nyah)
Origin: The initial species, B. rex, originated in the forests of northern India. Today, there are countless cultivars derived from this species enjoyed around the world.
Conditions: Considered perennials in tropical and semitropical climates, Rex begonias are frost tender and typically grown as annuals or houseplants in North America. They thrive in organic, sharp-draining soil and in shade with lots of humidity.
Care: Watering “on demand” (or when the soil is dry to the touch) is a great way to keep Rex begonias happy. Avoid soggy conditions, but do not allow plants to wilt. Give Rex begonias a diluted dose of organic, soluble food every four to six weeks during the growing season. Begonias do not grow or use fertilizer efficiently below 18C.
Overwintering: Rex begonias make excellent houseplants and can easily be overwintered indoors. To supply plants with adequate humidity, place containers on a tray of gravel, where runoff water may collect, evaporate, and raise the air-moisture level. Avoid placing plants near drafts.
Propagation: Although it can take up to six months to produce a new plant, leaf cutting is the most common form of propagation because leaves are the most readily available part of the plant. Seed can take an equally long time and leads to plant variability. You can harvest stems for cuttings; they typically root in about 20 days in favorable conditions.