Silver spike grass

Silver spike grass: how do you recognise it?

Habit

Dense, clump-forming plant with foliage to 50–60 cm and flower stems to 1 m that arch over; about 80 cm wide.

Leaves

Narrow, grey-green and slightly stiff; they roll up in dry weather. In autumn they turn straw-yellow.

Flowers

Long, loose, feathery panicles from June to September, silvery white at first, sometimes tinged purple, later golden brown.

Roots

Deep and fibrous; the grass does not spread by runners and stays neatly in place.

Winter

The dry plumes and straw-coloured leaves stay upright for a long time and give structure to the winter garden.

Flowering: June–September · Plants: March–May · Pruning: March

Why grow it?

• Exceptionally long flowering: from June to September, and the plumes stand well into winter.
• Silvery white plumes that move in every breeze and glow when backlit.
• Thrives in dry, chalky soil, where many border plants struggle.
• Very drought-tolerant and hardy: ideal for a gravel or steppe garden.
• The plumes look lovely in fresh or dried arrangements.

Silver spike grass: where does it grow best?

• Full sun: in shade it flowers less and the plumes flop.
• Well-drained soil, sand, loam or clay, neutral to chalky; poor soil is fine.
• Dry to normally moist; wet soil in winter makes the clump rot.
• Allow 70–80 cm per plant, so the arching plumes have room.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Dry or normal

Size

1 m tall, 0.8 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Balkan clary: Violet-blue spikes beside the silvery plumes, also on dry soil.
• Ice plant: Broad pink flower heads in late summer, in the same dry spot.
• Globe thistle: Blue, spiky globes for a true steppe garden.
• Purple coneflower: Flowers at the same time and looks lovely among the plumes.
• Lavender: A low, fragrant foreground on the same poor soil.

Silver spike grass: when and how to plant it?

Plant in March–May.

1. Plant from March to May: ornamental grasses establish best in spring.
2. Dig a hole twice as wide as the pot and loosen the soil; on heavy soil, mix in coarse sand or gravel.
3. Set the clump at the same depth as it was in the pot, no deeper, and firm the soil well.
4. Space plants 70–80 cm apart; it looks best in a group of three or five.
5. Water in well straight away and during dry spells in the first season.
6. Mulch with gravel or leave the soil bare; compost and fertiliser are not needed.

Care

Watering

Only in the first year during dry spells. After that it copes even in dry summers.

Feeding

Not needed: on rich soil the stems become floppy and the plumes fall over.

Spent plumes

Leave them until spring: they look good in winter and protect the heart of the clump.

Spring tidy

In March, cut away the old leaves and stems, or comb out the dead leaves with gloved fingers.

Renewing

Rejuvenate an old clump with a bare centre by dividing it in spring.

Tip: Plant it where the low evening sun shines through the plumes: backlit, they glow silver. Only cut back in March, so you can enjoy it all winter.

Silver spike grass: when to prune it?

Pruning months: March.

When: In March, before the new leaves really get going. Leave the grass standing all winter.

How:

• Cut the old flower stems off at the base.
• Cut the old leaves back to 10–15 cm above the ground, or comb out the dead leaves with gloved fingers.
• Spare the young green leaves already coming from the centre.

Caution: Do not cut back in autumn: an open centre stays wet in winter and rots more quickly, and you lose the lovely winter plumes.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In April–May, when the grass starts growing: cut the clump into pieces with a sharp spade, each with plenty of roots, and replant them straight away.

Seed

Sow in spring in a seed tray under glass and only plant out the young plants once they are sturdy. It takes a few years for them to reach full size.

Silver spike grass: how does it get through the winter?

Hardy to −25 °C.

• Very hardy, to about −25 °C: in Belgium no protection is needed.
• Leave the plumes and leaves standing: they look beautiful with frost on them and protect the centre.
• Wet soil is more dangerous than frost: make sure drainage is good.
• In a large pot: stand it on pot feet and give hardly any water in winter.

Diseases and pests

• Crown rot: The centre of the clump turns brown and soft, usually after a wet winter. Plant in well-drained soil and do not cut back in autumn.
• Flopping plumes: Caused by soil that is too rich, too much shade or too much water. Choose a sunny, poor spot and do not feed.
• Bare centre: In older clumps the middle dies and the grass grows in a ring. Divide it in spring and replant the vigorous outer pieces.
• Slow start: In the first year after planting the grass grows rather slowly. Water in dry spells and be patient.

Through the year

• February: Leave the plumes standing; they look lovely with frost.
• March: Cut old leaves and stems back to 10–15 cm. Plant.
• April: Plant. Divide old clumps.
• May: Plant. Water young plants in dry spells.
• June: First plumes, silvery white.
• July: Full flower. Cut plumes for a vase.
• August: Flowering. The plumes slowly turn golden brown.
• September: Last flowers. Pick plumes for drying.
• November: Leave leaves and plumes standing.
• December: Winter silhouette in the border.

Did you know?

• In the wild this grass grows on limestone screes in the Alps and other European mountain ranges.
• It was long called Stipa calamagrostis and is still often sold under that name, but botanists now place it in the genus Achnatherum.
• The species name calamagrostis refers to its resemblance to the reed grasses of the genus Calamagrostis.