Gloxinias are lovely houseplants with large leaves and colorful flowers. They're generally started from tubers-the short, thickened portion of an underground stem that measures one-and-a-half inches in diameter. Plant the tubers in five-inch or larger pots as needed.
Gloxinias grow best in a soil mixture of 50-percent organic matter, such as peat moss, which is available at most garden centers and nurseries. Most commercial potting soils are satisfactory, but if you prefer, you can blend your own using one part peat moss, one part compost, and one part perlite or vermiculite.
To plant the tuber, place the rounded bottom on the potting soil, and add enough soil mix to barely cover it. Water the tubers until the soil is saturated. For faster growth, place the potted tuber over a warm room heater or in another warm location where temperatures are 65 to 70 degrees Fahrenheit. Newly potted plants may require water every three to four days. Mature plants may require more frequent watering. Never allow gloxinias to become completely dry.
Once leaves emerge, fertilize your gloxinia with a liquid fertilizer, and be sure to follow the manufacturer's recommendations. Fertilize older plants every three to four weeks during the active growth period.
Gloxinias grow best near a south or west window during the winter. Insufficient light causes the stems to become long and spindly. Don't allow leaves to touch the glass, because it may result in freeze damage. Protect plants from direct sunlight after May 1.
Gloxinia plants require a short rest in the fall. As soon as the leaves begin to die, gradually withhold water. The resting tubers can be kept in a dark place until new growth appears in several weeks. Then bring your gloxinia back into a sunny part of the house to begin a new growth cycle.
For "Commonly used plant terms" refer to message number 2008.
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Updated Friday, April 19, 2013