Blue lyme grass

Sun

Full sun gives the strongest blue colour; tolerates light shade.

Water

Water regularly during establishment, then only during prolonged dry spells. Containers need more frequent watering.

Soil

Well-drained soil, especially sand or gravel; tolerates poor, salty and alkaline soils. Avoid persistently waterlogged ground.

Height

Leaves 2-3 ft (0.6-0.9 m); flower stems 3-4 ft (0.9-1.2 m)

Spread

3-6 ft (0.9-1.8 m) initially; spreads indefinitely by underground runners if uncontained

Flowers

Early to midsummer; dense, upright greenish flower spikes turn straw-coloured as they mature.

Foliage

Broad, stiff, pointed blue-grey leaves, often arching at the tips; usually die back in cold winters and may persist in mild climates.

Growth

Fast, with vigorous sideways spread once established

Care needed

High

• Deer resistant
• Drought tolerant
• Cold hardy
• Heat tolerant
• Wildlife

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

Difficulty

Hard

Toughness

Very tough

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

1. Planting day

   1.1 ft (0.35 m)

2. After 1 year

   2 ft (0.6 m)

3. After 2 years

   2.5 ft (0.75 m)

   full size

About 2 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

Safe

Native to

the UK

Invasive in

the US and Canada

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Grow in a large, sturdy container on paving where escaping roots can be spotted; do not rely on a bottomless pot for containment.
• Water through the first growing season, allowing the surface soil to dry between waterings.
• Avoid routine feeding in the ground; rich soil encourages more vigorous growth.
• Inspect nearby soil and drainage holes regularly, and remove escaping runners with their attached roots.
• Divide congested container plants in spring and refresh the potting mix.

Pruning. Cut old foliage and stems to 4-6 in (10-15 cm) above ground in late winter or early spring, before fresh growth develops. Remove unwanted flower spikes before seed matures, although underground runners are the main means of spread.

Late winter

Cut back weathered leaves and old flower stems before new shoots appear.

Spring

Plant or divide into secure containers; inspect existing plants for escaping runners.

Late spring

Water new plants during dry weather and remove shoots appearing outside their allotted space.

Summer

Check container moisture regularly and remove flower spikes before seed ripens if spread is a concern.

Autumn

Inspect drainage holes and surrounding ground for escaped roots; dispose of runners without dumping them in natural areas.

• Use in large containers beside paving, where the blue foliage contrasts with dark walls or stone.
• Combine contained plants with sea holly and thrift for a coastal planting.
• Use as a bold foliage accent beside fine-textured grasses or low stonecrops, keeping its roots separate.
• Repeat matching containers along a sunny terrace for a strong architectural rhythm.

Garden styles it suits: Coastal, Architectural minimal, Contemporary minimal, Dry gravel garden, Scandinavian and Blues and silvers.

Plant it with: Sea holly, Thrift, Lavender, Yarrow, Stonecrop and Russian sage.

Wildlife: Dense foliage can shelter small invertebrates. Flowers are wind-pollinated and provide little value to nectar-seeking insects; do not use it as a substitute for locally native dune vegetation.

• Aggressive runners invade nearby planting: lift escaped growth and remove the full length of each rhizome; move the parent plant into secure containment.
• Root or crown rot in wet soil: improve drainage or replant in a free-draining container, discarding rotten sections.
• Rust can produce orange-brown pustules on leaves: remove badly affected foliage, improve airflow and avoid wetting the leaves when watering.
• Brown leaf tips in containers often indicate drying out or congested roots: water thoroughly and divide or repot in spring.

Not known to be toxic to cats, dogs, horses or people. Stiff leaf edges and dry seed heads may cause mechanical irritation if chewed or handled.

Where it spreads. Spreads aggressively by rhizomes in gardens in the United States, Canada, the United Kingdom and Australia. It is introduced and considered invasive in parts of the North American Great Lakes region, including Michigan, Wisconsin and Ontario, where it can spread into sandy shore habitats. It is native to coastal parts of northern Europe, including Britain.

• Blue fescue (Festuca glauca)

  Forms small, compact tufts of very narrow, needle-like leaves rather than tall stands of broad leaves spreading by runners.

• Magellan's blue grass (Elymus magellanicus)

  Also has broad blue leaves, but forms a distinct tuft rather than sending out the long, vigorous rhizomes typical of blue lyme grass.

• Marram grass (Ammophila arenaria)

  Has narrower, tightly rolled, usually green to grey-green leaves rather than broad, relatively flat steel-blue blades.

The species name arenarius means 'of sandy places' in Latin, referring to its coastal sand habitat.

Propagation. Divide in spring, keeping rooted sections with healthy shoots. Seed can also be sown in spring, but seedlings may vary in leaf colour; never discard divisions or root-bearing soil in natural areas.

Accepted botanical name

Leymus arenarius

In the US and Canada

Introduced in Canada, Greenland and the lower 48 states.

Native range

Belarus, Belgium, Central European Rus, Denmark, Finland, France, Føroyar, Germany, Great Britain, Greece, Iceland and Ireland.

Measured

Soil pH 5.7 to 6.5. Average height 74 cm.

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