Lobelias grow in clumps of flowery spikes, attracting hummingbirds, butterflies and birds with bright-red blossoms. Lobelia's upright stalks grow 1 to 6 feet tall and are in bloom May through October. Despite being a short-lived plant, this herbaceous perennial self-seeds, becoming a constant presence in the garden. Lobelias grow both in moist ground along bodies of water and in pots placed inside ponds. Plan ahead to help the plant survive the winter.
Build a 2- to 3-inch mulch ring around the base of lobelias growing in the ground in northern climates. Use wood chips, dead leaves or straw to insulate the plants' roots. Leave 1 to 2 inches of space between the inner circumference of the mulch pile and the plant's stalk. Leafy stems develop at the base of lobelias, requiring exposure to sun and air.
Prune the dead foliage off lobelias growing inside a pond. Trim the plant back to 2 to 3 inches above the root crown. Push the planter to the bottom of the pond to prevent the crown from freezing. Weigh the pot down with rocks.
Remove the pot of pond-grown lobelias from the water as an alternative to Step 2. Trim the dead foliage and the plants' stems as described. Place the lobelias in a dark, unheated room at 4.44 degrees Celsius through the winter.