If your shady spots are looking a little dull and uninspired, you may want to consider Torenia fourneiri, which blooms generously and brightly in shade.
Their trumpet-shaped blooms come in several color choices; the primary species coloring is a dark blue-purple and lavender with yellow markings. Within each flower, a pair of stamens (the slender stalks) unites in a shape that resembles a wishbone, hence the plant’s common name. Moreover, the plants are deer-resistant and attractive to hummingbirds.
Although most varieties are compact, growing only 3 to 5 inches (7.5-12.5 cm.) tall, others will grow up to 3 feet (1 m.). Colors are also variable, with white, pink, red and blue species available. However, violet-blue is probably one of the most commonly seen. These plants make great additions in borders, along creeks or ponds, as ground covers, or in containers—especially hanging baskets.
Aside from keeping your plants sufficiently watered and fed, there isn’t much maintenance necessary. Deadheading (removing spent blooms) isn’t essential, though it can help to encourage more growth and flowering. Furthermore, if a plant looks scraggly, you can trim it back to about half its height.
Light
The ideal location for wishbone flowers is where it receives early morning sun and afternoon shade. If you live in a climate that has hot summers, pick a fairly shady location for your plants. It will not thrive in full sun.
Soil
Wishbone flower prefers organically rich, loamy soil with a slightly acidic to neutral soil pH. Excellent soil drainage is essential to prevent root rot. To improve the soil quality, consider mixing in some compost at the time of planting.
Water
Wishbone flowers require moderate but consistent moisture. Keep the soil moist, but make sure the plants aren’t sitting in soggy soil.
Temperature and Humidity
Wishbone flowers grow best in temperatures of 70 to 75 degrees Fahrenheit during the day and 65 to 70 degrees Fahrenheit at night. They can tolerate cooler temperatures, though frost will kill the plants. They also don’t like excessive heat or humidity and can benefit from a layer of mulch in hot climates to keep their roots cool.
Fertilizer
To keep wishbone flowers healthy and blooming, provide a balanced, all-purpose fertilizer roughly every few weeks throughout the growing season (spring to fall). You can either use a liquid fertilizer or a slow-release granule fertilizer, following label instructions.
Source: The Spruce: https://www.thespruce.com/growing-wishbone-flower-torenia-1402918
To grow torenia in containers, use a rich, well draining soil. Water often enough to keep the soil moist. Torenia is beautiful all by itself in a container, or it can be paired with another shade tolerant plant such as perilla. The perilla provides a dramatic backdrop of deeply colored foliage for the bold green foliage and colorful flowers of the torenia.
If you really love torenia, and would rather not be without it at the end of the growing season, torenia can be grown as a houseplant. Treat your indoor torenia to the indirect but bright light of a north or east facing window. Keep your soil moist, just as you would for your outdoor torenia. Feed your indoor plant monthly with a fertilizer high in phosphorous. This will support your plant’s ability to bloom.
