Lobelia plants are available in several varieties that range from annual to perennial plants. The lobelia plant is commonly found as a low-growing annual used as an edging plant, in rock gardens or in containers. The plant can be propagated through the collection of seeds which can be sown indoors eight to 10 weeks prior to the desired outdoor planting dating date. Plant the lobelia seedlings in a soil that is nutrient rich and in partial shade light conditions. Lobelia will bloom during the summer and fall months.
Purchase seeds or collect lobelia seeds after the flower blossoms turn to seed pods. Dry collected seeds and store them in a paper envelope until seeding time.
Fill a seed starting tray with sterile seeding medium or create your own by mixing equal portions of peat moss and perlite. Lightly moisten the medium with water when filling the tray.
Sprinkle the seeds over the surface of the seed starting medium. Lightly press the seeds into the soil but do not cover them. Cover the tray with a clear plastic cover to increase the humidity and moisture level during germination. Germination will occur in approximately three weeks.
Place the tray in a warm environment with indirect sunlight. The seeds need light to germinate, so make sure some is available during the daylight hours of the day. Open the tray cover daily to circulate air in the planting environment. Mist the soil lightly to prevent it from drying out.
Uncover the seed starting tray once growth has occurred. Place the seed tray under grow lights set at 3 inches above the seedling growth. Raise the lights as the seedlings grow. Continue to mist the soil daily with water to prevent it from drying out.
Transplant small seedling clumps into 2-inch pots once they reach a height of 1 1/2 inches. Continue to mist the pots with water daily.
Harden the plants outdoors once they reach a height of 3 inches. Set the plants outdoors in a shaded location for several hours a day to start with. Begin to increase the time the plants are out daily over a two week period until the plants are outside 24 hours a day. Bring the plants indoors or to a protected location if evening temperatures drop below 50 degrees Fahrenheit.
Plant the lobelia plants in an outdoor flower garden once there is no longer a risk of frost. Place the plant clumps 10 inches apart in the ground. Apply mulch around the plants for moisture retention. Water the plants regularly when there is less than 1 inch of rainfall per week.