How to Grow China Aster From Seeds

Fill peat or newspaper pots with a commercial seed starting mixture about six weeks before you intend to place your asters in the garden. Water the pots until the medium is moist but not wet, and do not allow the pots to stand in water. Using a seed germinating mat, warm the soil in the pots to 70 degrees Fahrenheit. Check the temperature using a temperature probe.

Plant two or three seeds per pot by dropping them on top of the warmed soil and just dusting with soil. Allow the seeds to have some exposure to sunlight to encourage germination. Mist the pots carefully using a hand-held sprayer until the top of the soil is moist.

Watch the seeds for signs of germination, and continue to mist them so they stay moist. Allow 10 to 14 days for seedlings to appear. Raise the humidity level by covering the pots with plastic or placing them in plastic bags if germination seems sluggish. Remove the plastic covers once germination occurs.

Thin the seedlings to one per pot once the first true leaves appear. Begin gradually exposing them to brighter sunlight as the seedlings develop. Continue to monitor the moisture level of the pots, and water when necessary; do not leave the pots in standing water.

Harden the seedlings off about a week before placing them outside full-time. Begin by placing them in a protected location for the warmest part of the day, and gradually move them to a spot near their permanent location. Increase the plants' exposure a little each day; too much sun too suddenly can cause sunburns or plant death.