What Are the Water Requirements for Petunias?

Seedlings

• Petunia seedlings require evenly moist soil. While the mature plants provide some drought tolerance, seedlings should not be allowed to dry out. Avoid wetting the foliage, as moist leaves are more prone to damping off and other fungal diseases. Water at the base of the plants, just enough to moisten the soil. Alternately, set the seedling pots in a tray of water and allow the soil to soak up moisture from below. Empty the water tray once the soil surface is moist in the pots. Seedlings require watering when the soil surface just begins to feel dry.

Bedding Plants

• Petunias are mildly drought-tolerant, but regular watering helps keep the flowers in constant bloom. Water the beds when the top 6 inches of soil begins to dry. Most bedding plants require once-a-week watering, but in sandy soils more frequent irrigation may be needed. Water at the base of the plants until the top 6 inches of soil is evenly moist but not soggy. Petunias need approximately 1 inch of water a week, from either rainfall or irrigation. Spreading varieties of petunias may require more frequent watering. Mulching over the bed helps retain soil moisture so frequent watering isn't necessary.

Container Plants

• Containers dry out more quickly than garden beds, which petunias tolerate fairly well. Check the moisture in the containers daily and water when the top 2 inches of soil is beginning to feel dry. Water at the base of the plants until the excess drains from the bottom of the pot. Allowing the water to drain ensures moisture gets down into the root zone of the petunias where they need it most. Containers usually need watering every one to two days. Since petunias prefer full sunlight, the containers may dry out more quickly during hot, dry weather and require two daily waterings during these periods.