Blue hair grass

Blue hair grass: how do you recognise it?

Habit

Compact, dense, evergreen tuft about 30 cm tall and wide, flower spikes included.

Foliage

Narrow, stiff and blue-grey thanks to a waxy coating.

Flower

Dense, narrow, cylindrical spikes in June and July, silvery green or purplish at first, straw-coloured later.

Roots

Fibrous root system that tolerates drought but not wet feet.

Use

Rock garden, gravel garden, edges, containers and green roofs.

Flowering: June–July · Plants: March–May and September–October

Why grow it?

• Blue-grey, evergreen tufts that give colour in every season.
• Compact, cylindrical flower spikes in June and July.
• Drought tolerant and fully hardy: ideal for sand and gravel.
• Stays low: handy for rock gardens, gravel, edges and containers.
• Low maintenance: no pruning and no feeding needed.

Blue hair grass: where does it grow best?

• Full sun: in shade it loses its blue colour and the tuft falls open.
• Poor to ordinary, free-draining soil: sand or loam, neutral to chalky. Very well suited to sandy soil.
• Dry: very drought tolerant. Wet, heavy soil is its worst enemy.
• Plant 25–30 cm apart, in groups of at least three for the best effect.
• Needs no shelter: it tolerates wind and heat.

Light

Sun

Soil type

Sand or loam

Acidity

Neutral or chalky

Moisture

Dry

Size

0.3 m tall, 0.3 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Thyme: An aromatic carpet in the same dry, sunny spot.
• Stonecrop: Fleshy leaves and late flowers, with the same need for sun and dry soil.
• Lavender: Blue-purple flowers and grey leaves on free-draining soil.
• Yarrow: Yellow or orange flower heads in summer above the low tufts.

Blue hair grass: when and how to plant it?

Plant in March–May and September–October.

1. Plant in March–May or in September–October, when the soil is not frozen.
2. Loosen heavy soil and mix in coarse sand or fine grit. On sandy soil there is nothing to improve.
3. Set the plant at the same depth as in its pot, with the crown at soil level.
4. Plant 25–30 cm apart, in small groups or rows.
5. Water in well after planting and then only in prolonged drought during the first season.
6. Lay a thin layer of grit or chippings around the plants; no organic mulch.

Care

Water

In the first season during prolonged drought. After that rarely needed; in a pot or container, now and then.

Feeding

Not needed: poor soil keeps the tuft compact and blue-grey.

Combing

In spring, pull the dead leaves out of the tuft with your fingers or a hand rake.

Spent flower spikes

Leave them as a straw-coloured accent or cut them off in August.

Dividing

A tuft that goes bare in the middle is divided every 3–4 years in spring.

Tip: Plant it in small groups on poor, free-draining sandy soil and do not feed: the tuft stays compact and blue-grey. On heavy soil, mix grit into the planting hole.

Blue hair grass: when to prune it?

When: Do not prune. Just pull the dead leaves out of the tuft in March–April.

How:

• Comb through the tuft with your fingers or a hand rake: the dead leaves come loose.
• Cut off the spent flower spikes in August or leave them as a straw-coloured accent.
• Do not cut the tuft itself short: it recovers poorly.

Caution: Do not cut it hard back: an evergreen tuft recovers poorly from this.

Pruning calendar and basic rules

Propagation

Division

In March–April or September: lift the tuft, divide it into pieces with roots and replant them straight away. Do this every 3–4 years.

Seed

In spring on seed compost at 15–20 °C, barely covering the seeds. Seedlings grow fairly quickly, but the blue colour can vary.

Blue hair grass: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy down to about −25 °C: no protection needed in Flanders.
• Wet feet are the danger: ensure good drainage and leave the foliage standing in winter.
• In a pot or container: raise it on feet so surplus water drains away and place it sheltered against a wall.

Diseases and pests

• Winter wet: Brown or rotting tuft in spring because the soil is too wet. Improve drainage with grit and plant on a slight mound.
• Bare centre: A tuft dies out in the middle after a few years. Divide it in spring and replant the living outer pieces.
• Rust: Orange, powdery pustules on the leaves in a damp summer. Pull out affected leaves and keep the tuft airy.
• Loss of blue colour: The blue fades in shade or rich soil. Give full sun and do not feed.

Through the year

• March: Pull dead leaves out of the tuft. Plant or divide.
• April: Plant or divide.
• May: Plant. The flower spikes form.
• June: Flowering begins.
• July: Flowering. Little or no water needed.
• August: Cut off spent spikes or leave them.
• September: Plant or divide.
• October: Plant.
• November: Make sure drainage is good.

Did you know?

• The genus Koeleria is named after Georg Ludwig Koeler (1765–1807), a German botanist.
• The species name glauca means blue-grey, after the waxy coating on the leaves.