Perennial flax

Sun

Full sun; flowering and stem strength decline in shade.

Water

Water regularly during establishment, then mainly during prolonged dry spells. Established plants tolerate drought but dislike persistently wet roots.

Soil

Well-drained sandy, gravelly or loamy soil, preferably of low to moderate fertility. Tolerates chalk and alkaline soil; avoid wet, heavy clay.

Height

1-2 ft (0.3-0.6 m)

Spread

1-1.5 ft (0.3-0.45 m)

Flowers

Late spring to midsummer; sky-blue, five-petalled flowers, usually opening in the morning and dropping their petals later that day.

Foliage

Narrow, blue-green leaves on slender, branching stems; usually deciduous, though some foliage may persist through mild winters.

Growth

Moderate; often flowers in its first year from an early sowing.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   1.1 ft (0.35 m)

3. After 2 years

   1.3 ft (0.4 m)

4. After 3 years

   1.5 ft (0.45 m)

   full size

About 3 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Native to

Canada

Growth rate

Moderate

• Water newly planted flax when the root zone begins to dry; avoid keeping it constantly damp.
• Do not routinely feed; rich soil and excess nitrogen encourage floppy growth.
• Use a thin gravel mulch rather than piling compost or bark against the crown.
• Grow in an open, sunny position so stems remain upright without staking.
• Allow a few seedheads to ripen if you want replacement plants; remove unwanted seedlings while small.

Pruning. After the main flowering flush, shorten flowering stems by about half to tidy the plant and encourage a possible lighter repeat bloom. Cut remaining dead stems back to the basal growth in late winter or early spring.

Late winter

Remove dead stems and check that the crown is not sitting in wet soil or buried under mulch.

Spring

Sow seed where plants are to grow, or plant young specimens without disturbing their roots.

Late spring

Water young plants during dry weather and remove weeds around their bases.

Summer

Trim after the main flowering flush, leaving some seedheads if you want self-sown replacements.

Autumn

Collect ripe brown seed capsules before they open, or thin self-sown seedlings.

Winter

Keep drainage outlets clear and avoid watering dormant plants unless conditions are unusually dry.

• Plant in loose groups near the front of a sunny border, where the fine stems soften heavier-looking perennials.
• Combine with catmint, yarrow and low ornamental grasses for a drought-tolerant planting with contrasting textures.
• Scatter through gravel gardens, allowing occasional seedlings to fill open spaces.
• Use in sunny cottage gardens with white daisies and pink flowers for a soft, informal colour scheme.

Garden styles it suits: Cottage garden, Dry gravel garden, Wildflower, Pollinator garden, Blues and silvers and Low-maintenance.

Plant it with: Catmint, Yarrow, Lavender, Salvia, Shasta daisy and Blue fescue.

Wildlife: Flowers provide pollen and nectar for bees and other visiting insects. It is native to parts of Europe and Asia, not a substitute for locally native flax species in North American or Australian habitat plantings.

• Root and crown rot in wet soil: improve drainage or move plants to a raised, gravelly bed; discard badly rotted plants.
• Floppy stems and poor flowering: provide full sun, stop feeding and avoid overly rich soil.
• Aphids on tender shoots: wash them off with water and encourage ladybirds and other predators.
• Rust, seen as orange pustules on leaves or stems: remove affected material, improve airflow and avoid wetting foliage when watering.

Not an edible flax. Flax plants can contain cyanogenic compounds, particularly in seeds and young growth, which can cause serious poisoning if enough is eaten. Species-specific evidence for Linum perenne in cats and dogs is limited; keep seeds and plants away from pets, horses and children, and seek veterinary or medical advice after substantial ingestion.

• Lewis flax (Linum lewisii)

  This western North American species is extremely similar and is sometimes sold under the same common names. Flower colour and height are not reliable distinctions;

• Common flax (Linum usitatissimum)

  The crop grown for linen and linseed is an annual, usually taller and more upright, with generally broader leaves. Perennial flax forms a lasting crown and returns in following seasons.

Linum is the Latin name for flax, and perenne means perennial, referring to the plant's ability to live for more than two years.

Propagation. Sow seed directly outdoors in spring, or in autumn where winters and drainage allow. It self-seeds in open soil but is usually easy to thin. Seed is generally more successful than division because established plants dislike root disturbance.

Accepted botanical name

Linum perenne

In the US and Canada

Native in Alaska and Canada. Introduced in the lower 48 states.

Native range

Altay, Austria, Belarus, Buryatiya, Central European Rus, China North-Central, China South-Central, Czechoslovakia, East European Russia, Germany, Hungary and Inner Mongolia.

Measured

Average height 45 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.