How to Plant Broadleaf Sage Seeds Indoors

Combine 3 parts potting soil, 1 part coarse sand and 1 part fine sand to create a growing mix suited to the needs of broadleaf sage.

Fill a 2-inch-deep seedling tray with the soil mixture to within 1/2 inch of the top. Even out the surface but do not firm the soil.

Sprinkle the broadleaf sage seeds onto the soil so that approximately three seeds fall per square-inch. Cover the seeds with a thin layer of fine sand to hold them in place while still allowing light to reach them.

Mist the soil until the top half-inch feels moderately moist but not soggy. Maintain moisture in the top half-inch of soil while the broadleaf sage seeds germinate, but allow the surface to dry out slightly between waterings to keep the soil from becoming waterlogged.

Set the seedling tray near a source of very bright light, either near a large window or under a fluorescent lamp. Choose a spot with direct light for six to eight hours each day.

Apply bottom heat to the broadleaf sage seeds using a propagation mat set to 78 degrees F. Lower the temperature to 60 degrees F at night to mimic the natural warming and cooling cycle found outdoors.

Watch for germination in two weeks. Thin the seedlings to one per square inch once they produce a pair of mature leaves, which are oblong, fleshy and slightly hairy.

Transplant the broadleaf sage seedlings into individual 3-inch starter pots two weeks after thinning them. Fill the starter pots with the soil mixture described in Step 1.

Keep the individually potted broadleaf sage plants in a warm, sunny spot until they put on significant growth. Plant them in a permanent pot or outdoors in a sunny, sandy bed once all danger of frost has passed.