Fill a nursery flat with seed starting mix. These mixtures contain several types of materials that help prevent damping off, a fungal disease of seeds and seedlings. Moisten the mix until water runs out of the bottom. Allow the mix to drain until it is moist, not saturated.
Scatter the seeds on the surface of the mix and cover with a 1/4-inch layer of sand or vermiculite. Slip the flat into a plastic bag and seal it.
Place a heat mat in an area where the seeds will get lots of light, such as near a south-facing window. Set the thermostat to 68 to 70 degrees Fahrenheit and place the bagged flat on top. Germination times vary, according to species -- generally 12 to 60 days. If you are growing Tanacetum coccineum, parthenium, balsamita, cineariifolium, coccineum, demetrii, niveum, huronense or vulgaris, lower the heat mat's temperature to 24 to 39 degrees Fahrenheit for two to four weeks if the seeds do not germinate within four weeks.