How to Grow Basil Indoors in High Altitudes

Fill the flat with seed-starter mix. Irrigate the soil.

Broadcast the small basil seeds on the surface ½ inch apart. Cover the seeds with ¼-inch-thick layer of seed-starter mix.

Mist the top layer of soil with water to moisten the basil seeds. Continue to keep them hydrated until germination.

Place the flat on an electric seed-propagation mat with the thermostat set to 70 degrees Fahrenheit. Basil seeds germinate within one week. Keep the newly sprouted seedlings on the propagation mat at 70 degrees until transplantation to individual pots.

Move the tender young seedlings to indirect sunlight. Maintain the soil consistently moist. At high altitudes, the air tends to be very dry. Monitor the soil's moisture closely and prevent it from drying out.

Transplant seedlings with two sets of leaves to individual 2-inch pots filled with well-aerated potting mix. A blend that contains sphagnum peat moss, for example, is an ideal option. Water the plants until excess flows out of the drainage holes. Keep the soil consistently moist.

Introduce basil plants to full sun gradually. Place a grow lamp 6 to 12 inches above the basil plants for 10 to 12 hours daily if you cannot provide the herb at least six hours of sun at home.

Harvest leaves and sprigs after the plant grows 6 inches tall. Pluck individual leaves or cut a stem ¼ inch above a set of leaves. The plant will regrow, but as an annual herb, basil dies at the end of the season even if you grow it indoors. Sow next year's seeds in spring.