How to Grow: Lobelia

Lobelia erinus

Other Name

Edging lobelia

Sun Requirements

Full sun, part sun

Bloom Period and Seasonal Color

Early summer until fall in blue, violet, pink, and red

Mature Height x Spread

4 to 6 inches x 4 to 12 inches

Added Benefits

Attracts beneficials

Lobelia is a widely popular, low growing, bushy or trailing annual flower. It is often matched with alyssum in containers and garden beds. It can just litter the ground or a container in color. The traditional variety has electric blue or violet colored flowers, but newer varieties stretch the color range to pink and red, too. The foliage and flowers are delicate, but lobelia flowers in abundance, blooming all summer right until frost. In spring and fall lobelias grow well in full sun. However, in summer the sun may be too strong for this plant and some shade will help keep it in bloom. Bushy plants grow well grouped in beds, while trailing varieties are perfect for container, window boxes, and hanging baskets.

Where, When and How to Plant

Lobelia seedlings take up to 10 weeks growing indoors when sown from seed. The seed can be difficult to germinate, and the plants are widely available. Many gardeners purchase seedlings from local garden centers in spring. Grow lobelia in full to part sun after all danger of frost has passed. Grow lobelia in well-drained, compost amended, soil or containers filled with potting soil. If the bed or container is in a warm area, grow in part sun since the midsummer heat can cause lobelia to stop flowering and dieback. Plant bushy varieties 6 inches apart and trailing varieties up to 12 inches apart.

Growing Tips

Keep plants well watered, especially during hot spells in mid summer. Cut back plants after the early summer blush of flowers to promote more branching and flowering later in summer and fall. Fertilize every 3 weeks with a complete organic plant food to keep plants blooming.

Regional Advice and Care

Lobelias are stunning plants that attract butterflies and beneficial insects. If the plant stops flowering or even dies back in mid summer, simply keep it well watered and fertilized. It will bounce back with the cooler weather of late summer. In Northern regions of New England, it often continues flowering non-stop, all summer long.

Companion Planting and Design

Bushy lobelia varieties look great in front of a flower border or mixed with other annuals in containers. Trailing types are perfect in containers to cascade over the edge. Grow lobelia paired with alyssum to give a blue and white combination of colors. Other trailing flowers that look good with lobelia include petunias, fuchsias, and love-in-a-mist. Grow lobelia as the “spiller” in containers paired with tall zinnias, salvia, and other annuals.

Try These

The ‘Cascade Series’ featured trailing lobelia varieties of various colors. ‘The Rainbow Series’ is a bush-type that is great planted in flower borders or edges. ‘Crystal Palace’ is a stunning, blue heirloom variety. ‘Bed O’ Roses’ features different shades of pink and rose colored selections.

Excerpted from my book, New England Getting Started Garden Guide.