The Torenia fournieri, also known as the wishbone flower is an annual bloomer which flowers in summer and fall. It originally grew in Southeast Asia--specifically the Vietnam area. Flowers range in color, depending on the variety of Torenia you plant. They are white, blue, purple, yellow and violet. As long as the plant has partial shade and the appropriate amount of water, it will grow up to 12 inches tall. The flower tends to have weak stems, so pruning torenia will help keep it strong and healthy.
Remove spent blooms as soon as they die off. Use gloved fingers to pinch off the petals. This will free up nutrients to go to other parts of the Torenia, as well as improve the annual's appearance.
Cut off the top 3 inches of Torenia's branches after flowering is complete. This will keep the plant from dropping seeds and causing additional plants to grow.
Thin out the branches to increase air and sunlight circulation. Both lessen the likelihood of disease and insect infestation. Cut off branches that are non-productive and stringy in appearance.
Prune diseased and dead branches twice per year. Wait until after they flower, then cut them off with shears where they meet healthy branches.
Look for powdery mildew on the Torenia's leaves. It's characterized by white or gray splotches on the top of leaves and causes them to shrivel up and die. Remove the affected leaves in the fall and destroy them to avoid spreading the mildew.