Torenia (or Torenia Fournieri) is an annual that thrives in a warm climate with compost-enriched soil. The plant blooms in summer and fall, with flowers that are purple and medium blue. With an average height of 12 to 18 inches, the Torenia does well in borders. It is often started from seeds, but because the seeds are very small, start them as least 10 weeks before the last frost is expected.
Keep the plant in the full sun to semi-shade. If it's not doing well, it may not be receiving enough sun. Move it to a more suitable location.
Check the moisture of the soil often by touching it with your finger. Torenia needs moist, well-watered soil, especially when it's hot or windy. However, don't allow standing water, as this can cause root rot.
Apply water-soluble fertilizer every 2-3 weeks to keep the plant growing well. This is especially important during the blooming periods. Mix the fertilizer with water as per the manufacturer's instructions.
Check the soil with a pH test kit obtained from a nursery or hardware store. If it isn't acidic, falling between 5.6 and 7.5, make adjustments.
Increase the pH by 1.0 point to make the soil more alkaline. Add 4 oz. of hydrated lime per square yard for sandy soil and 8 oz. per square yard in loamy soil. Add 1.2 oz. of ground rock sulfur per square yard to reduce the soil pH by 1.0 point, to make it more acidic.
Deadhead the plant to keep it more attractive in appearance. Remove the dead blooms by hand.
Watch for small seedlings to appear in the spring. Torenia will sometimes drop its seeds, causing new plants to grow. If you don't want them, simply pull them out.