Petunias are tender perennials grown across much of the United States as summer annuals. These prolific bloomers create a nonstop show of color from spring until fall, but do require consistent care. These rapid growers, particularly the trailing and wave varieties, consume copious amounts of water. Those grown in the soil typically need deep watering once a week, but those planted in hanging baskets or containers may require daily watering. Without adequate water, petunias may cease blooming, or foliage may wilt and die, within a day or two during hot, dry weather. With quick intervention, petunias can often be revived.
Cut back foliage on overly dried petunias to within several inches of the soil level. If foliage remains green, the chances of success are good. If leaves have yellowed, become brittle or begun to turn brown, cutting the petunia back may revive it.
Submerge the plant pot into a bucket of room-temperature water. Bubbles will rise to the surface as water displaces the air in the soil and pot.
Allow the plant to soak until air bubbles cease. Remove from the bucket of water and allow excess water to drain from the pot.
Place the petunia plant in an area that receives partial shade. Areas that receive morning sun, but are sheltered from the hot afternoon sun, are ideal.
Check the soil daily and water when the soil feels dry to 1 inch below the surface of the soil. Water deeply until water runs free from the bottom of the pot. Establish a routine for watering to keep the soil moist.
Watch for signs of new growth. New leaves will form at the tips of cut stems within a week or two, if you caught the plant before the roots died. Growth typically flourishes, returning the petunia plant to health within a few weeks.
Apply water-soluble fertilizer when new growth appears. Follow the manufacturer's directions for mixing and applying the solution. Repeat in two to four weeks to promote healthy growth.