Rhodochiton is also known as purple bell vine. Rhodochitons are perennial vines which are typically grown as annuals since they are killed by frost. They grow to reach approximately 10 to 20 feet in height. Rhodochiton is indigenous to Mexico and is hardy in USDA zones 9 through 10. The 2- to 2 1/2-inch long, tubular shaped flowers of rhodochitons are such a dark purple they are often mistaken for being black.
Fill a seed-starting tray or planting cells with sterilized seed-starting mix 6 to 8 weeks prior to the last spring frost. Compact the soil in each planting receptacle until you're sure it's well firmed down.
Plant three to four rhodochiton seeds into each cell and cover with approximately 1/16 of an inch of soil. If planting in a seed starting tray, randomly sprinkle seeds over the soil. Press the seeds firmly into the surface and scatter 1/16 of an inch of soil over the seeds. Spritz the surface of the soil with warm water until it's well dampened.
Place the tray or cells into a clear plastic bag or cover tightly with a layer of plastic wrap. Put the covered tray or cells in a warm, light-filled area. The ideal temperature range for germination is between 60 and 70 F. Provide at least 8 to 10 hours of light a day, but keep the seeds out of direct sunshine.
Germination can be sporadic, taking from two weeks to 30 days. Once seedlings appear, remove the plastic bag or plastic wrap.
Put the pots into an irrigation tray. Keep the seedlings moist, but not drenched with water. Fill the tray with 1 inch of water every 3 to 4 days, or before the soil starts to dry out. Once seedlings reach about 2 to 3 inches in height, transplant them into larger growing receptacles, such as 4-inch pots.
Use potting mix to fill up 4-inch pots half full. Push up from the bottom of a cell to remove a rhodochiton seedling. If growing from a seed starting tray, remove rhodochiton seedlings by digging out each seedling carefully using a spoon.
Place a rhodochiton seedling into a pot. Ensure the roots are sitting firmly upon the soil. Hold the seedling level while you fill up the pot with soil. Pack down the soil in the pot. Water until the soil is well dampened.
Put the transplants into a cooler area, approximately 60 to 65 F. Provide at least 10 to 12 hours of light a day. Once seedlings are 4 to 5 inches tall, transplant them outside, or into larger growing containers.