Lithotoma spp.

rock isotome

Attracts Pollinators Attracts Butterflies Deer Resistant Container Friendly

SunFull Sun – Part Shade

Overview

Lithotoma spp. is a small genus of herbs in the bellflower family, Campanulaceae (subfamily Lobelioideae), native to Australia, and closely related to and sometimes merged with Isotoma spp.. Plants are low, tufted to erect annuals or short-lived perennials 4-16 inches (10-40 cm) tall, with narrow, toothed or lobed leaves and milky sap. From spring into summer, slender stalks carry star-shaped flowers with five narrow, pointed lobes, in white, pale blue, or violet, each up to about 1 inch (2.5 cm) across. The genus grows in seasonally moist, open sites such as rock crevices, granite outcrops, streamsides, and disturbed ground, in full sun to light shade. The milky sap contains irritant alkaloids that can inflame skin and eyes on contact. Plants are adapted to a wet growing season followed by a dry rest, and many behave as annuals, completing their cycle from seed in a single season. Free-draining soil and seasonal moisture suit them, while heavy, wet, or shaded conditions reduce flowering.

Native Range

Lithotoma spp. species are native to Australia, where they grow in seasonally moist habitats including granite outcrops, rock crevices, creek margins, and open disturbed ground across southern and eastern regions.

Suggested Uses

Grown in rock gardens, gravel gardens, seasonal container displays, and as warm-season annuals in beds and pots. Native-plant gardens in Australia use the species in outcrop and dry-streambed plantings where seasonal moisture collects.

How to Identify

Identify Lithotoma spp. by low tufts or erect stems with narrow, toothed leaves and milky sap, carrying star-shaped flowers with five narrow, pointed lobes in white to blue or violet. The flowers sit singly on slender stalks. The irritant milky latex and rock-outcrop habitat help separate it from similar small herbs.

Appearance

Size & Dimensions

Height4" - 1'4"

Width/Spread4" - 1'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Spring Summer

Flowering occurs mainly from spring into summer, generally September to January in the native Southern Hemisphere range, following seasonal rains. Star-shaped flowers open on slender stalks over several weeks. Small capsules follow and release the tiny seed as they dry.

Detailed Descriptions

Flower Description

White, blue, or violet

Foliage Description

Green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-10 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 Range5.5 - 7.0(Neutral)

357912

Soil Types

sand rocky loam

Drainagewell drained

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

Lithotoma spp. grows in full sun to light shade in free-draining, sandy or gravelly soil with moisture through the growing season. Plants follow a pattern of active wet-season growth and a drier rest, and many are grown as annuals from seed. Even moisture during growth and flowering supports the display, while heavy, waterlogged, or deeply shaded soil reduces it. The milky sap is a skin and eye irritant. Most species suit mild-temperate to warm climates and are frost-sensitive, grown as warm-season annuals where winters are cold.

Pruning

Spent flower stalks are trimmed to prolong flowering and limit excess self-seeding. Annual plants are cleared once they finish and set seed. Cutting back is done after flowering to tidy perennial species, and the cut stems release irritant sap.