Lobelia is a low-growing, flowering perennial prized for its richly colored blooms that range from white and soft pink to purple and deep cobalt blue. As a relatively low, mounding plant that reaches just a few feet in height at most, it is often used in front of beds and borders to soften the transition between surfaces or plantings such as lawn grass or walkways. While not an invasive, creeping plant lobelia can become leggy and lean down over the soil, cascading gently into adjacent planting areas. Careful pruning can control the spread and rejuvenate leggy growth to keep the edge plantings full and upright and within the confines of the planting bed.
Trim the lobelia branches extending beyond the edge of the planting bed with a pair on long-blade, scissor-type pruning shears.
Hold the shears roughly parallel with the edging line and trim off the stems that cross over the line.
Work from one end of the edged bed to the other or out from the middle toward each end. Be mindful to keep the cut line straight or parallel and equidistant from the edge of the curved bed for a professional result.