Is the Lobelia Plant an Annual or a Perennial?

Lobelia is a perennial plant that is often considered an annual because growing conditions must be perfect for it to survive to rebloom another year. More than 360 species of lobelia are grown as annuals, perennials or shrubs.

...
Trailing lobelia is used as an edging plant in many gardens

Lobelia Erinus

The trailing lobelia (Lobelia erinus) is the plant most commonly found growing along the edge of the flower bed. It may be treated as a perennial or an annual plant, depending on the climate of the location in which it is grown. With perfect growing conditions, it will grow year after year. In harsh climates it will die after flowering and setting seeds.

Lobelia Siphilitica

The great blue lobelia (Lobelia siphilitica) is considered a perennial herb. It has erect stems, ranges from 2 to 3 feet in height, and blooms in late summer.

Lobelia Inflata

Often called Indian tobacco, Lobelia inflata is considered a poisonous annual plant. It is said that Native Americans chewed and smoked the leaves of the Lobelia inflata. Hence, the nickname. This type of lobelia can survive in poor soil.