To grow snapdragons, plant the seeds in containers of vermiculite six to eight weeks before the last expected frost of the season. After planting the seeds, set the containers in a sunny location, and maintain temperatures of 60 to 70 degrees Fahrenheit. Allow the seedlings to reach 3 to 4 inches in height. Then, pinch the tips back to grow compact, bushy snapdragons. Move the snapdragons to the garden after the last expected frost of the season.
Allow the seeds to germinate for 10 to 20 days before moving the seedlings outdoors. To encourage successful germination, place a heated seed mat under containers of newly planted seeds. After the first blooms appear, cut the plant back by one-third to increase flower production.
Continue deadheading flowers over the course of the growing season. Apply general-purpose fertilizer to the plants every four to six weeks, or work slow-release fertilizer into the soil before planting snapdragons.
Provide snapdragons with 1 inch of water per week, or water the plants with a soaker hose when the top 2 to 3 inches of soil feels dry. Avoid overhead watering techniques. Prune the plants in midsummer to maintain bushy, compact growth. At the end of the growing season, cut the stalks off at ground level.