Blue rush 'Blue Arrows'

Sun

Full sun for the strongest blue colour and upright growth; tolerates light partial shade.

Water

Keep consistently moist to wet. Established plants tolerate brief drying, but prolonged drought causes browning.

Soil

Moisture-retentive loam or clay, including poorly drained soil; tolerates neutral to alkaline conditions particularly well.

Height

2-3 ft (0.6-0.9 m)

Spread

1-2 ft (0.3-0.6 m)

Flowers

Small, inconspicuous brown flower clusters appear near the stem tips in summer.

Foliage

Evergreen. Narrow, cylindrical, finely ridged blue-grey stems form a dense upright clump; true leaves are reduced to sheaths at the base.

Growth

Moderate

Care needed

Low

• Deer resistant
• Cold hardy
• Heat tolerant
• Wildlife

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

Difficulty

Easy

Toughness

Fairly tough

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

1. Planting day

   1.1 ft (0.35 m)

2. After 1 year

   1.7 ft (0.51 m)

3. After 2 years

   2.2 ft (0.67 m)

4. After 3 years

   2.5 ft (0.75 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

Safe

Native to

the UK

Growth rate

Moderate

• Water whenever the root zone begins to dry, especially in containers.
• At pond edges, keep the crown at water level or beneath no more than about 2 in (5 cm) of water.
• In ordinary garden soil, apply a thin layer of compost in spring; avoid heavy feeding.
• Divide congested clumps in spring, keeping several healthy shoots and roots in each division.
• Check pots regularly in summer and protect them from prolonged freezing in colder regions.

Pruning. In late winter or early spring, remove brown stems at the base without cutting healthy blue stems. If most of the clump is winter-damaged, cut it back to about 2-4 in (5-10 cm) before new growth starts.

Late winter

Remove dead stems and assess winter damage before new shoots emerge.

Spring

Plant or divide clumps and water thoroughly.

Spring

Add a thin compost dressing to plants in garden beds.

Summer

Check soil moisture frequently, particularly in pots and newly planted beds.

Late summer

Remove flower clusters before seeds ripen if unwanted seedlings are a concern.

Autumn

Leave healthy stems standing for winter structure and move vulnerable containers to a sheltered position.

• Plant in repeated groups along a pond edge for upright blue-grey accents.
• Use in rain gardens where the soil stays moist between rainfall events.
• Grow in containers with moisture-loving trailing plants for a contrast in shape.
• Pair with broad-leaved hostas or bergenias in moist, lightly shaded borders.
• Combine with sedges and flowering wetland perennials for an informal waterside planting.

Garden styles it suits: Modern, Contemporary minimal, Architectural minimal, Bog garden, Blues and silvers and Winter interest.

Plant it with: Siberian iris, Marsh marigold, Japanese iris, Hosta, Astilbe and Bowles' golden sedge.

Wildlife: Dense stems provide shelter for small invertebrates around wet ground. The wind-pollinated flowers offer little value to nectar-feeding insects.

• Brown tips or dying stems in summer usually indicate dry roots; soak the root zone and water more consistently.
• Winter browning can occur in exposed or very cold sites; remove damaged stems in spring and shelter container-grown plants.
• Rust can cause rusty spots on stems; remove affected growth, improve spacing and avoid wetting stems unnecessarily.
• A crowded clump may develop a dead centre; lift and divide it in spring, discarding the dead section.

Not known to be toxic to people, cats, dogs or horses. No part is considered a food plant, and the stiff stems can irritate the mouth if chewed.

• Soft rush (Juncus effusus)

  Usually has smoother, greener stems with continuous white pith; hard rush has more visibly ridged, blue-grey stems and interrupted pith.

• Blue fescue (Festuca glauca)

  Forms shorter, rounded tufts of narrow grass leaves with separate flower stalks; 'Blue Arrows' has taller, upright cylindrical rush stems and needs much wetter soil.

The common name hard rush refers to its firm stems, while 'Blue Arrows' describes the cultivar's blue-grey colour and sharply upright growth.

Propagation. Divide clumps in spring to retain the cultivar's blue colour and upright habit. Seed-grown plants may differ from the parent.

Accepted botanical name

Juncus inflexus

In the US and Canada

Introduced in Canada and the lower 48 states.

Native range

Afghanistan, Albania, Algeria, Assam, Austria, Baleares, Baltic States, Belarus, Belgium, Bulgaria, Canary Is. and Cape Provinces.

Measured

Soil pH 7.5 to 8. Average height 55 cm.

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