The Wave petunia is a hybrid petunia introduced in 1995 and designed to spread over the ground and have a longer and more prolific bloom period than the old garden varieties. The flowers are larger and the colors are more vibrant. They are used as bedding plants, but are also popular for use in hanging baskets, where they cascade as much as 3 feet over the sides of the container. Occasionally, Wave petunias begin to decline before they reach their full potential. They can be saved by identifying the problem and following a few steps.
Difficulty: Moderately Easy
Fertilize the Wave petunias every two weeks with a water-soluble plant fertilizer if they are only showing slow growth and sparse flower development. If the Wave petunias are planted in the ground, apply the fertilizer at the strength recommended on the fertilizer container label. If they are planted in hanging baskets, dilute the fertilizer to half-strength and add it to the plants once a week. This will keep them healthy, green and blooming throughout the growing season, and give them a good start.
Spray with a garden fungicide that is approved for flowering annuals, available at most garden centers, if fungal problems appear. Fungal problems often appear near the center of the plant as leaves turn black or begin to curl. They may also show up as white spots on the flowers. Soak the plant completely with a fungicide mixed to the correct proportions by following the instructions on the label. Overuse of fungicides will kill a Wave petunia.
Water the Wave petunia plant as often as needed to keep the soil moist, but not wet, during the growing season. Water the plants as close to the root system as possible and do not allow the foliage to get wet during the process to prevent fungal disease. This is especially true in hanging baskets, where the foliage of the center of the plant remains wet because of the need to water the roots every day in warm weather. Place the nozzle of the watering device in the foliage near the root system to avoid wetting the foliage.
Relocate hanging baskets that are showing wilting and stress from exposure to direct sun. In the southern half of the United States, petunias cannot tolerate the intense direct sun of July and August and will die if planted in full sun. High dappled shade, such as under a tall deciduous shade tree, or exposure to the first four hours of sun in the morning is best for growing petunias in hanging baskets in the southern states. Never allow Wave petunias to wilt from heat stress and lack of water; they may not recover.
Incorporate peat moss into the planting mix by adding it around the petunia plants if they are planted in the ground. The optimal planting mix for Wave petunias is 1/2 potting or garden soil and 1/2 peat moss. Do not use garden soil in a hanging basket.
Hanging baskets benefit from several handfuls of peat moss over the top of the soil, especially if the top layer of soil is washed away by frequent watering. Be sure the hanging basket where the Wave petunia is planted is well drained. Peat moss acidifies the soil pH and holds moisture. The acidity provided by the peat moss helps control fungal problems.