Is this plant invasive?

It can be quite aggressive in ideal conditions and may spread rapidly by self seeding.

Does it need full sun?

It prefers partial to full shade and will struggle in hot, direct sun.

Plant guide

Green alkanet.

Pentaglottis sempervirens

Pronounced pen-tah-GLOT-iss sem-per-VYE-renz

Also known as Alkanet, Evergreen bugloss, Green Alkanet, bird's-eye, blue alkanet, evergreen alkanet

Green alkanet is a hardy perennial that brings a splash of bright blue to shady corners. It spreads readily and stays green through most of the winter. You will love how it brightens up woodland areas in your garden.

At a glance

Care level: Easy
Plant type: Perennial
Light: Partial shade to full shade
Indoor light: Medium light
Water: Every 5 to 7 days
Mature size: 3 feet
Growth rate: Fast
Hardiness: USDA 6 to 9
Bloom time: Late spring to mid summer

Care

Keep the soil consistently moist but not waterlogged to support its vigorous growth. Watch for wilting during dry spells, as this plant prefers a steady supply of water. You can easily manage its spread by removing spent flower stalks before they go to seed.

Watering: Water regularly to keep the soil evenly moist throughout the growing season.
Feeding: Apply a balanced liquid fertilizer every two months during the spring and summer.
Pruning: Cut back flower stems after blooming to encourage a second flush and prevent unwanted self seeding.
Repotting: Divide large clumps every one to two years to maintain plant vigor.
Soil: Moist, fertile, well drained soil
Soil pH: Neutral to alkaline
Temperature: -15 to 30°C
Humidity: 40 to 70%

Safety

People: The plant contains pyrrolizidine alkaloids which can cause liver damage if ingested in large quantities.
Pets: This plant is generally considered non toxic to cats and dogs.
Children: The bristly hairs may cause skin irritation if handled by children, and the plant should not be ingested.
Contact allergens: The stiff, bristly hairs on the leaves and stems can cause mechanical skin irritation.
Airborne allergens: There is no significant evidence of respiratory allergies associated with this plant.
Edibility: This plant is not considered edible and should be avoided for consumption.

How to identify it

Bright blue star shaped flowers
Large ovate dark green leaves
Rough bristly hairs on foliage
Clump forming perennial habit

Height: 0.45 to 0.9m
Spread: 0.45 to 0.6m
Leaves: dark green, semi-evergreen
Flowers: bright blue, 1 to 1.5cm
Fruit: brown, late summer

Problems to watch for

Powdery MildewCommon
Slugs and SnailsCommon
AphidsUncommon
Leaf SpotUncommon

By symptom

Plant problems by symptom

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Growing it

Propagation: division, seed
When to plant: spring, autumn

Plant in areas where you can easily manage its spread, as it can become a nuisance in small beds.

Grows well with

Ferns · They share a love for moist, shaded soil conditions.
Hosta · The broad leaves of hostas contrast well with the bristly foliage of the alkanet.

Similar species

Borage · They share similar flower shapes and family characteristics.

Science

Family: Boraginaceae
Genus: Pentaglottis
Order: Boraginales
Class: Magnoliopsida
Native range: Southwestern Europe.
Conservation: This plant is common and not of conservation concern.

It grows in moist, shaded habitats where it outcompetes smaller plants for space.

Value to wildlife: nectar source
Pollinators: bees, butterflies
Uses: woodland gardens, shady borders, pollinator support

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 1/9
Soil reaction: 6/9
Light: 3/9
Temperature: 5/9
Moisture: 6/9
Nutrients: 6/9

Taxonomy resolved against GBIF.

Questions people ask

Is this plant invasive?: It can be quite aggressive in ideal conditions and may spread rapidly by self seeding.
Does it need full sun?: It prefers partial to full shade and will struggle in hot, direct sun.

Where the name comes from

The genus name Pentaglottis comes from Greek meaning five tongues, referring to the five scales in the flower throat, while sempervirens means always green.

Good to know

It is a member of the borage family.
The plant is often called green alkanet.
It thrives in the dappled light of woodland edges.

Also in

Plants for shade

Keep your green alkanet growing

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This guide was generated with AI on September 26, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.