What hardiness zones is Glandora diffusa suitable for?

Glandora diffusa is suitable for USDA hardiness zones 6, 7, 8.

What are the sun requirements for Glandora diffusa?

Glandora diffusa requires Full Sun.

How much water does Glandora diffusa need?

Glandora diffusa has Low water needs.

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Broadleaf Evergreen Shrubs

Glandora diffusa

lithodora

Boraginaceae

Southwestern Europe (Spain, Portugal, SW France)

At a Glance

TypeSubshrub

HabitSpreading

FoliageEvergreen

Height6–12 inches (15–30 cm)

Width12–24 inches (30–60 cm)

Maturity3 years

Growing Zones

USDA Hardiness Zones

6 - 8

Zone 6

Zone 7

Zone 8

These zones indicate the coldest temperatures this plant can typically survive.

Frost Tolerancehardy

Key Features

Attracts Pollinators

Attracts Butterflies

Deer Resistant

Drought Tolerant

Container Friendly

Maintenancelow

Overview

Glandora diffusa is an evergreen subshrub reaching 6–12 inches (15–30 cm) tall with a spread of 12–24 inches (30–60 cm). Stems are prostrate to low-mounding and wiry, rooting at nodes where they contact soil. Leaves are narrow, lance-shaped, 1/2–1 inch (13–25 mm) long, dark green with a rough texture from stiff spreading hairs on both surfaces; arranged alternately. The plant forms a dense, spreading mat. From March through June (and sometimes beginning in February in mild years), 5-lobed tubular flowers approximately 1/2 inch (13 mm) across appear in dense terminal clusters; buds are pink, opening to an intensely saturated true blue — one of the most vivid blues available in garden plants. Individual flowers fade through purple-blue as they age, so a plant in peak bloom shows pink buds, open true-blue flowers, and aging purple-blue blossoms simultaneously. Growth rate is moderate; plants approach mature spread in 3–4 years. Requires excellent drainage and acid soil; declines rapidly in waterlogged or alkaline conditions. Drought tolerant once established. Formerly classified as Lithospermum diffusum.

Native Range

Native to southwestern Europe, including Spain, Portugal, and southwestern France, growing in heathlands, rocky hillsides, and open scrubland in well-drained, acidic soils at low to moderate elevations.

Suggested Uses

Planted in rock gardens, raised beds, dry-stone walls, or border edges where excellent drainage is assured. Used as a low groundcover on slopes where the trailing habit and drought tolerance provide weed suppression. The vivid blue spring color creates striking sweeps when planted in masses. Effective in containers where drainage can be controlled. Not suited to heavy clay soils, wet sites, or alkaline conditions.

How to Identify

Identified by the prostrate to low-mounding habit of wiry stems bearing narrow hairy lance-shaped leaves 1/2–1 inch (13–25 mm) long, combined with the intensely true-blue 5-lobed tubular flowers from late winter through spring. The vivid blue flower color — among the truest blue in cultivated plants — is the primary identification feature. Buds are pink, transitioning to blue on opening. Leaves are rough-hairy on both surfaces. Distinguished from other blue-flowered groundcovers by the narrow hairy leaves, the pink bud/true-blue flower/purple-aged flower color progression, and the requirement for acid, well-drained soil.

Appearance

Size & Dimensions

Height6" - 1'

Width/Spread1' - 2'

Reaches mature size in approximately 3 years

Colors

Flower Colors

blue

pink

purple

Foliage Colors

dark green

Bloom Information

Bloom Period

~12 weeks

Late-winterSpring

Flowers March through June in USDA zones 6–8, occasionally from late February in mild years. Terminal clusters of 5-lobed tubular flowers approximately 1/2 inch (13 mm) across. Buds pink; open flowers intensely true-blue; aging flowers purple-blue. The three color stages are visible simultaneously on a plant at peak bloom. Total bloom period 10–14 weeks.

Detailed Descriptions

Flower Description

Intensely true-blue (buds pink; aging flowers purple-blue)

Foliage Description

Dark green, rough-hairy both surfaces; narrow lance-shaped, alternate

Growing Conditions

Sun Requirements

Full Sun

Partial Shade

Requires 5-8 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 Range5.0 - 6.5(Acidic)

357912

Soil Types

sandloamrocky

Drainage

well drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

3–4 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Requires excellent drainage — the most critical cultural requirement. Plants in heavy clay or waterlogged soil decline within one season. Plant in sandy or gritty, well-drained, acid soil (pH 5.0–6.5); do not add lime. In the Pacific Northwest, raised beds or rock garden settings provide the drainage this plant needs. Full sun produces the most prolific bloom; partial shade is tolerated but reduces flowering significantly. Water weekly for the first growing season; established plants are drought tolerant and need irrigation only during extended summer dry periods (6+ weeks). Do not fertilize with high-phosphorus or alkaline fertilizers. Mulching with fine bark or gravel maintains soil moisture without compaction.

Pruning

Lightly shear or trim back by one-third after the main bloom flush (late June) to encourage compact growth and a secondary flush of flowers. Do not cut into old bare woody stems — the plant does not regenerate from bare wood. Annual light trimming after bloom maintains a tidy mat and prevents the center from becoming woody and open.

Pruning Schedule

summer

Maintenance Level

low

Container Growing

✓ Suitable for container growing

⚠️ Toxicity Warning

Non-toxic