Snapdragons can also be direct-sown in the garden a few weeks before the last expected frost. However, snapdragons are relatively slow-growing, so when grown from seeds they are often started indoors six to 12 weeks before the last expected frost. Keep seedling trays at about 12-14 C.
Use a general seed starting mix or ordinary potting soil, and simply press the seeds onto the surface of the soil. Position the tray under bright lights placed just a few inches above the tray—snapdragon seeds need light to germinate so do not cover with soil. Keep the light on for a full 16 hours per day, gradually moving it higher as the seedlings grow.
When seedlings have developed about six true leaves (about 3 to 4 inches tall), pinch off the top of the stem, which will encourage branching and bushiness. Transplant snapdragons outdoors a couple of weeks before your last frost date. Snapdragons can handle a light frost or two.
Do not let snapdragons sit in soggy soil. Cut plants down to the height of 20 cm after their first blooms have died to encourage additional blooming.
Snapdragons are fairly inexpensive to purchase as nursery seedlings and easy to grow from seeds, but if you wish you can also propagate them from stem cuttings.
Cut a 5 cm section of the stem just below a leaf node on a healthy parent plant. Remove the lower leaves and dip the bottom of the cutting in rooting hormone. Plant the cutting into seed starter mix or potting soil, covering the pot with a plastic bag or dome to keep the cutting humid. When a good root system develops, you can remove the cover and continue growing in a bright window or under artificial lighting. Transplant outside about the time of the last frost in your area.