How Well Does a Snapdragon Grow Indoors & Outdoors?

Basic Growing Conditions

• Snapdragon seeds germinate best in cool soil that is 60 to 65 degrees Fahrenheit. Once seedlings appear, they excel in very bright light or direct sunlight to develop lots of leaves in a balanced, rounded plant. Plant growth, flower production and duration of flower spikes last longest when daytime temperatures are between 60 and 75 F and nighttime lows are from 40 to 55 F. Snapdragons tolerate light frosts without harm.

Indoor Growing

• Only grow snapdragons indoors if you own a solarium or greenhouse that provides abundant sunlight or very bright diffused light levels. Growing snapdragons in containers next to a window doesn't provide enough light to produce lots of flowers and the plants will become leggy and severely lean toward the light. Aphids occur when plants don't receive enough sunlight. Nurseries grow snapdragons in winter and spring to raise to a large, flowering size for customers to purchase and transplant outdoors. These production facilities are cool in temperature but supply lots of even, widespread light.

Outdoor Growth

• Snapdragons do not grow well outdoors when temperatures get warmer than 85 F, such as in summer in most of the Southern United States. Hot summers cause plants to wilt, become scrawny, stop flowering and more quickly succumb to drought or fungal diseases. Conversely, snapdragons also do not grow well when temperatures are always below freezing or winters are very wet. Nighttime lows below 20 F can kill plants if daytime temperatures don't warm above 40 F. In the Northern U.S., Pacific Coast and at high elevation, snapdragons grow and bloom well from spring to fall since summers aren't hot.

Recommendations

• Because of snapdragon's need for lots of sunlight and relatively cool, springlike temperatures, plan on growing the best plants with lots of flowers outdoors. Start seeds eight to 10 weeks prior to the last spring frost in seed trays indoors. Transplant seedlings outdoors after threat of frost to grow to their fullest potential. Only in mild winter regions should snapdragons be planted in late fall or winter. Plants may also be sown in outdoor cold frames to overwinter and then be planted in the garden in early spring.