Isotoma spp.

Laurentia

Attracts Pollinators Attracts Butterflies Container Friendly

SunFull Sun – Part Shade

HardinessZones 7–11

Overview

Isotoma is a genus of low-growing annuals and perennials in the bellflower family (Campanulaceae), native mainly to Australia with a few species elsewhere. Plants form mounds or creeping mats 3-18 inches (8-45 cm) tall, with finely divided or narrow leaves and slender stems that exude a milky, irritant sap when cut. The five-petalled, star-shaped flowers are most often blue to violet, sometimes white or pink, about 1-1.5 inches (2.5-4 cm) across in the mounding I. axillaris and smaller in the mat-forming I. fluviatilis. Flowering continues over a long season from late spring through autumn. In the wild the genus grows on rocky outcrops, along streambanks, and on seasonally moist ground. Mounding species are grown as warm-season container and bedding plants, while the creeping blue star creeper is used as a groundcover and lawn substitute in mild climates. Plants need full sun to part shade and moist, well-drained soil; the mounding kinds are frost-tender. The milky sap can irritate skin and eyes on contact.

Native Range

Isotoma spp. is native mainly to Australia, with a few species in other warm regions. Plants grow on rocky outcrops, along streams and seasonal watercourses, and in moist open ground.

Suggested Uses

Isotoma spp. mounding types are grown in containers, hanging baskets, and summer bedding, while the creeping species is planted as a groundcover, between stepping stones, and as a lawn alternative in mild regions. Both are used where long, continuous flowering is wanted.

How to Identify

Look for a low mound or creeping mat of slender stems with narrow or finely cut leaves, bleeding a milky sap when broken. The star-shaped, five-petalled flowers are usually blue to violet and held on thin stalks over a long season. The mat-forming I. fluviatilis hugs the ground, while I. axillaris makes a rounded cushion.

Appearance

Size & Dimensions

Height3" - 1'6"

Width/Spread8" - 2'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~16 weeks

Spring Summer Fall

Isotoma spp. flowers over a long season from late spring into autumn, peaking in summer. The blue, star-shaped flowers open continuously without deadheading, scattered across the foliage. In frost-free climates the creeping species can flower nearly year-round.

Detailed Descriptions

Flower Description

blue to violet, sometimes white or pink

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Soil Types

loam sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

tender

Time to Maturity

1 year

Care & Maintenance

Care Guide

Grow Isotoma spp. in full sun to part shade on moist, well-drained soil, keeping the root zone evenly damp through the growing season. The mounding species are grown as frost-tender annuals or container plants and bloom without deadheading. The creeping blue star creeper tolerates light foot traffic and is used between paving and as a lawn substitute in zones 7 and warmer. Trim mats after the main flush to keep them dense. Cut stems release a milky latex that can irritate skin and eyes.

Pruning

Isotoma spp. needs little pruning. Shear mounding plants lightly after the first heavy flush to encourage rebloom, and trim creeping mats to keep them flat and dense. Cut back frost-damaged growth in spring where plants are grown as tender perennials.

Container Growing

✓ Suitable for container growing

Minimum container size: 1 gallons

⚠️ Toxicity Warning

Toxic to pets and humans

Perennial