Isotoma axillaris
Common Name: laurentia 
Type: Herbaceous perennial
Family: Campanulaceae
Native Range: Australia
Zone: 10 to 11
Height: 0.50 to 1.00 feet
Spread: 0.75 to 1.00 feet
Bloom Time: June to frost
Bloom Description: Light blue to purple blue
Sun: Full sun
Water: Medium
Maintenance: Medium
Suggested Use: Annual
Flower: Showy


Winter hardy to USDA Zone 10. In St. Louis, plants are grown as annuals. Start plant seed indoors about 10-12 weeks before last spring frost date. Plant outdoors after last frost date. Grow in average, medium moisture, well-drained soils in full sun. Cuttings for special plants may be taken indoors in late summer for overwintering. Containers may also be overwintered by bringing them indoors before first fall frost and placing same in a cool but sunny spot with reduced watering.

Noteworthy Characteristics

Isotoma axillaris, commonly called blue stars, star flowers, rock isotomes or laurentias, ia native to frost-free areas of Australia. This is a woody-based perennial that grows as an upright mound of branched stems to 6-12” tall. It may be grown outdoors year-round only in frost free areas. In St. Louis, they are typically grown as annuals. Features light blue to purple blue, star-shaped flowers (to 1.5” diameter). Flowers bloom from summer to fall. Long, deeply-dissected leaves (to 5” long). Synonymous with and sometimes marketed as either Solenopsis axillaris or Laurentia axillaris.

Genus name comes from the Greek words isos meaning equal and toma meaning a section. The segments of the corolla are equal.

Specific epithet means borne in the axil.


No serious insect or disease problems. Watch for aphids. Sap from plant stems may cause skin and/or eye irritation in some individuals.


Beds or containers.