Perennial Overview: Lobelia


Discover how to grow Lobelia with instructions on starting seed, transplanting, site selection, care and maintenance, water and fertilization requirements, and  pests and diseases.

Lobelia Stats at a Glance

Botanical Name: Lobelia erinus

Common Name(s): Dwarf annual lobelia, edging lobelia

Height: 4-10”

Soil Conditions:  Well-drained, fertile, loamy

Sun: Full sun/partial shade

Soil pH Conditions: 5.5-6.5

Planting Instructions

Can I Start Lobelia from Seed?

Lobelia can be propagated through seed and division.

Division. Lobelia will benefit from division every one to three years.  Divide in the spring or fall.  May develop a central woody clump that should be removed and discarded.

Seed. Because seeds germinate slowly, start indoors.


To start indoors, fill individual peat pots with a fertile commercial soil starter and moisten.  Sprinkle the seeds on the surface of the soil. Press them lightly into the soil to ensure contact with growing medium. Place in a room with a constant temperature of 70-75°F.  Cover with clear plastic wrap to maintain the soil moisture and temperature.  Keep the soil moist.  When seedlings appear, remove the plastic wrap and move to a sunny location.


When to Start Seeds: >10-12 weeks prior to planting
Time to Germination: 14-21 days
Light/Darkness Requirements: Light
Optimal Temp. for Germination: 70-75°F



When Do I Plant Lobelia?

Lobelia are cold sensitive and should not be planted until after the last frost and the soil has reached at least 70°F.  They will germinate much more quickly in warmer soil.  You can hasten the warming of the soil with black plastic mulch.

Soil Temperature: 70-75°F


Where Do I Plant Lobelia?

Lobelia plants perform best in loamy, slightly acidic, well-drained soil high in organic matter but will grow in nearly any good garden soil that receives full sun/partial shade and is well-drained. Incorporating several inches of organic matter into the soil when preparing the bed will improve growth and development. Plant in the shade in areas that are hot and humid.


Soil Type: Well-drained, fertile, loamy
Sun Exposure: Full sun/partial shade
Soil pH: 5.5-6.5


How Far Apart Do I Plant Lobelia?

Space plants 6” apart.

Lobelia Plant Care and Maintenance

Once established, most perennials require very little routine care and maintenance.

How Often Should I Water Lobelia?

For many perennials, average rainfall is sufficient to keep the plants healthy.  Supplementation may be necessary in droughty conditions.

The key to watering Lobelia is to maintain a consistent moisture level.  This is especially important during hot weather. The soil should be moist to a depth of 6”.  Allowing the soil to dry out between watering will result in a shallow root system.

Water the soil around the plant. Overhead watering will encourage disease.  Drip irrigation is best.

Mulch around the plant will help to lock in moisture.


Should I Fertilize Lobelia?

Most perennials do not require a specific fertilization regiment.  Fertilizing decisions should be based on a soil test.  If a soil test cannot be obtained and you feel that your perennial bed would benefit from fertilization, keep it light.  Work in a small amount of a low nitrogen fertilizer, such as 5-10-5 around the plants in the early spring and once or twice at six-week intervals.

Fertilize the soil around the plant at least 6” from the plant base. Irrigate into the soil.

Re-fertilize if you cut back the plant.


Additional Care Instructions

When the plant is young and developing, pinch the growing tip often to encourage a bush habit.

Following blooming, cut plant back to half its original size to encourage further blooming.

Lobelia Diseases

The most common diseases associated with this plant include leaf spots, rusts, and smuts.

Lobelia Pests

The most common pests associated with this plant include slugs and snails.



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