Wave petunias are big, bright, sprawling petunias that will light up the flower bed all summer with little care. Wave petunias are relatively new in the gardening world, valued for their ability to spread out rapidly and bounce back quickly from hot or cold weather or hard rains. Versatile plants, Wave petunias as ground covers, in hanging baskets or sharing a large patio container with other brightly colored annuals. Plant Wave petunia seeds indoors 10 to 12 weeks before the last frost in your area.
Fill a planting tray with commercial potting soil that you have dampened ahead of time. Sprinkle a few Wave petunia seeds on top of the soil and spray the top of the soil with a fine mist. Don't place any soil on top of the seeds.
Cover the tray with a sheet of clear plastic wrap. Place the tray in a warm room where the temperatures will be maintained between 70 and 85 degrees F. The seeds should be exposed to bright, but indirect sunlight.
Remove the plastic from the tray when the seeds sprout, which should take seven to 10 days. Move the tray to a cooler room with daytime temperatures of about 60 degrees F. and nighttime temperatures about 5 degrees F cooler.
Place the seedlings in bright sunlight. The seedlings will benefit from being placed under a grow light or a florescent light fixture for 16 to 18 hours per day. Allow 4 to 6 inches between the plants and the light.
Transplant the seedlings into peat pots or celled containers when the seedlings have three true leaves. True leaves are the leaves that emerge after the tiny, initial seedling leaves.
Fertilize the Wave petunia seedlings every week, using a liquid plant fertilizer diluted to half strength.
Harden off the Wave petunia seedlings in preparation for planting outdoors. Place the seedlings outdoors in a warm, protected spot during the day for about a week. Bring the seedlings indoors at night.
Plant the Wave petunias outdoors when all danger of frost has passed. Prepare a spot sunny spot in well-drained soil by spading the soil to a depth of 8 to 10 inches. Work in 2 to 4 inches of manure or compost.
Use a trowel to dig a hole for each Wave petunia. The hole should be just large enough to accommodate the seedling's root ball. Place the seedling in the hole and tamp soil lightly around the roots. Allow at least 24 inches between each plant, as Wave petunias will sprawl.
Water the seedlings immediately. Keep the soil moist at all times, as Wave petunias require more water than standard petunias. Don't allow the soil to become drenched, as soggy soil can cause the plants to rot.