Germinating Impatiens Seeds in a Greenhouse

Fill plug flats, which are plastic flats with typically 36 or 72 individual cells, with a sterile seed-starting medium. Test the pH with a tester kit to see if it meets the impatiens needs of a pH between 5.5 and 6.0.

Empty the seeds in a shallow bowl. Moisten a toothpick and touch a single seed with its end. Place the seed onto the medium surface.

Sow seeds on the medium and lightly moisten the medium by watering it directly or misting. Cover the plugs with a thin layer of vermiculite, recommends J. Raymond Kessler Jr., a horticulture professor at Auburn University. Cover the flats with clear plastic to maintain the 100 percent humidity that impatiens prefer for germination.

Place the flats on a seed-heating mat out of direct sunlight, perhaps under a shelf in the greenhouse, to maintain a temperature at 72 to 75 degrees Fahrenheit until the shoots emerge.

Apply a calcium-based fertilizer two to three days after seeding.

Remove the plastic and the heating mat after the seedlings emerge. Maintain the greenhouse temperature at 68 to 72 at night and 70 to 75 during the day. Ventilate the greenhouse in the last week of plug production so that nighttime temperature lowers to 60 to 62 to harden off the seedlings.