Germinating Rosemary in Flats

Soaking and Sowing

• Rosemary seeds have a low germination rate of about 30 to 50 percent. To optimize germination, soften the seed coat by soaking the seeds for four to six hours in a bowl of water. Then fill a seed-starting flat with moist, sterile, seed-starting mix up to a 1/2 inch from the top. Sprinkle the seeds on the surface and lightly tap them into the soil with your finger. Avoid covering them, because they need light exposure to germinate.

Temperature and Light

• After sowing the seeds, cover the flat with a plastic bag or a piece of plastic wrap to promote soil-moisture retention. A temperature range of 65 to 70 degrees is required for germination. To provide the seeds with light, hang two, 40-watt, cool-white fluorescent lamps about 6 inches above the seed-starting flat. Keep the lamps on for 16 hours a day. Check the soil daily, and if needed, spray water to keep it moist -- not wet.

After Germination

• Germination will set in after 15 to 25 days. The moment the sprouts emerge, remove the plastic from the flat. Continue the light exposure and move the lamps up as the seedlings grow so they're always 6 inches above the plants. Alternatively, move the flat into a sunny, south-facing window and rotate it periodically so the young plants grow upright and don't have to reach for the light. When the seedlings are about 10 weeks old and large enough to handle, transplant them to individual pots.

Transplanting

• After all frost danger has passed and the night temperature is consistently above 55 degrees, transplant the seedlings in a sunny area of the garden with well-drained soil that has a pH range between 6.0 and 7.0. Space the plants at least 12 inches apart. Rosemary doesn't tolerate temperatures below 17 degrees. If you live in a cool area, consider growing the seedlings in containers so you can move them indoors during the winter or when there's a threat of cold weather.