Introduction

Lobelias are small plants, 3 to 10 inches tall, that are covered with the most vivid blue flowers imaginable from early summer until frost (Figure 1). Lobelias have either very compact growth quite suitable to edgings or mass plantings, or long trailing stems, which will gently tumble over the edges of a container or raised bed, providing a bold splash of color wherever used. Cultivars are available with flowers of blue, violet, pink, white, or purple, often with a contrasting white or yellow eye.

General Information

Scientific name: Lobelia erinus

Pronunciation: loe-BEEL-lee-uh air-RYE-nuss

Common name(s): lobelia

Family: Labeliaceae

Plant type: annual

USDA hardiness zones: all zones (Figure 2)

Planting month for zone 7: May

Planting month for zone 8: Apr

Planting month for zone 9: Mar; Sep; Oct

Planting month for zone 10 and 11: Feb; Oct; Nov; Dec

Origin: not native to North America

Uses: container or above-ground planter; mass planting; border; attracts butterflies; cascading down a wall

Availability: grown in small quantities by a small number of nurseries

Description

Height: 0 to 1 feet

Spread: 1 to 2 feet

Plant habit: spreading

Plant density: dense

Growth rate: fast

Texture: medium

Foliage

Leaf arrangement: alternate

Leaf type: simple

Leaf margin: crenate

Leaf shape: linear; obovate

Leaf venation: not applicable

Leaf type and persistence: not applicable

Leaf blade length: less than 2 inches

Leaf color: green

Fall color: not applicable

Fall characteristic: not applicable

Flower

Flower color: white; blue; pink; purple, violet

Flower characteristic: showy

Fruit

Fruit shape: no fruit

Fruit length: no fruit

Fruit cover: no fruit

Fruit color: not applicable

Fruit characteristic: inconspicuous and not showy

Trunk and Branches

Trunk/bark/branches: not applicable

Current year stem/twig color: green

Current year stem/twig thickness: medium

Culture

Light requirement: plant grows in full sun

Soil tolerances: occasionally wet; clay; sand; acidic; loam

Drought tolerance: unknown

Soil salt tolerances: unknown

Plant spacing: 6 to 12 inches

Others

Roots: not applicable

Winter interest: not applicable

Outstanding plant: not particularly outstanding

Invasive potential: not known to be invasive

Pest resistance: long-term health usually not affected by pests

Use and Management

Lobelia performs best in cool weather but is sensitive to frost. In warmer regions, lobelia should be planted in partial shade but can grow in full sun where summers are cool or hazy. Although lobelia will cease flowering when temperatures are too warm, they will quickly recover when temperatures drop in early fall. Provided with rich, fertile, well-drained soil and abundant moisture, lobelia is very easy to grow and quite a spectacular little plant.

Many cultivars are available: 'Blue Moon' has dark blue flowers; 'Cambridge Blue' has clear, soft blue flowers on compact, upright 4- to 6-inch plants; 'Crystal Palace', bronze-green leaves, dark blue flowers on compact plants; 'Paper Moon' has white flowers; 'Rosamunde', carmine red flowers with a white eye; 'White Lady'and 'Snowball', pure white flowers; 'Blue Cascade', 'Fountain' series, 'Hamburgia', and 'Sapphire' have trailing forms, suitable for hanging baskets or raised planters. 'Sapphire' has purple flowers with a white eye and is one of the best trailing lobelias.

Plants should be cut back after each flush of flowering to encourage new blossoms.

Propagation is by seed which germinates readily, with blooms appearing in four months.

Pests and Diseases

No pests are of major concern.

Damping-off, stem rot, root rot, if conditions are too damp.