The designation "safe" assumes that you're not making snapdragon tea or using any part of the plants as an herbal medicine. Individuals may have an allergic reaction to handling some plants that contain no known toxins.
Snapdragons are short-lived perennials typically grown as annuals in U.S. Department of Agriculture plant hardiness zones 4 through 11. In USDA zones 9 through 11, they can be planted in autumn for winter color. They like cool weather but don't do well in summer heat of these warm zones.
Cultivars of the 40 species of snapdragons are grouped as tall, from 2 to 3 feet tall; intermediate, 1 to 2 feet tall; short, 9 to 12 inches tall; dwarf, 4 to 9 inches tall; and trailing varieties. They're best planted from 10 to 14 inches apart in full sun, but they can tolerate some shade.
Basics of Care
Work 1 pound of slow-release 12-6-6 fertilizer into the top 6 inches of 50 square feet of space before you plant snapdragons. Apply 1 1/2 to 2 1/2 pounds of 10-10-10 water soluble fertilizer over the same area every three to four weeks as a side dressing.
Snapdragons like moist soil. Water them when the top 1 inch of soil is dry to the touch.
Pinch the tips of 2-to-4-inch-tall snapdragons to grow more flowers. If you remove flowers as they mature, the plants will grow more flowers later in the season.
Insects and Diseases
Pesticides are seldom effective in treating the aphids that sometimes afflict snapdragons, causing their foliage to turn brown in hot weather. Fungal plant rust may cause yellowed leaves, small flowers and early death. Spacing plants properly to let air circulate helps avoid rust, and resistant varieties are available. Proper spacing also helps avoid the fungal disease anthracnose that discolors leaves and causes sunken spots on the stems. Destroy plants infected with anthracnose.