Lyme grass

Lyme grass: how do you recognise it?

Habit

Creeping grass that forms broad, loose mats from its rhizomes; leaves up to 60 cm, flower spikes up to 1 m tall.

Leaves

Broad, stiff and flat to rolled, blue-grey from a waxy coating; in winter they fade and become ragged.

Flowers

Dense, upright spikes of 15–30 cm in June–August, grey-green at first, later straw-coloured.

Roots

Long, creeping rhizomes that spread vigorously every year, also under paths and other plants.

Hardiness

Very hardy (to −30 °C) and tolerant of salt and wind.

Flowering: June–August · Plants: March–May and September–October · Pruning: February–March and August

Why grow it?

• One of the bluest ornamental grasses: a cool accent among grey and silver plants.
• Grows where almost nothing else will: in dry sand, in the wind and even in salty sea air.
• Native to our coast and ideal for a dune or seaside garden.
• Its rhizomes bind loose sandy soil and banks.
• After its first summer it needs hardly any watering.

Lyme grass: where does it grow best?

• Full sun: in shade the leaves lose their blue colour and the plant flops open.
• Poor, free-draining soil: sand is ideal, but it grows in any dry soil, acid to chalky.
• Dry: it dislikes wet soil in winter.
• It tolerates wind and sea wind, so it suits the coast and open, exposed spots.
• Allow at least 1 m of space and plant it in a large pot or inside a root barrier 40–50 cm deep.

Light

Sun

Soil type

Sand

Acidity

Not fussy

Moisture

Dry

Size

1 m tall, 1 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Sea holly: Silvery blue and spiny: together they create a real dune feel.
• Sea kale: Large grey-blue leaves and white flowers in May–June, another coastal plant.
• Sea thrift: Pink flowers on low cushions at the front.
• Lavender: Purple against blue-grey, in the same dry, sunny spot.
• Catmint: Lilac flowers and grey leaves, just as drought-tolerant.

Lyme grass: when and how to plant it?

Plant in March–May and September–October.

1. Plant in March–May or in September–October.
2. First sink a root barrier of sturdy plastic, 40–50 cm deep with the rim 5 cm above ground, or choose a large pot of at least 40 cm.
3. Dig a hole twice as wide as the root ball; on heavier soil mix in coarse sand or gravel for drainage.
4. Set the plant at the same depth as it was in the pot and firm the soil well.
5. Water thoroughly after planting and again in dry spells during the first weeks.
6. Mulch with gravel or sand, not compost: rich soil makes it floppy and even more vigorous.

Care

Water

Only in long dry spells during the first year. After that it is not needed, even in hot summers.

Feeding

Not needed. Fertiliser and compost make it spread even more and turn the leaves less blue.

Runners

Every spring, chop off runners outside the chosen spot with a sharp spade and pull out the rhizomes.

Flower spikes

Cut them off if you mainly want the blue foliage: the plant stays neater.

In a pot

Water now and then in summer; divide and repot every two or three years.

Tip: If you want it in a border, first sink a root barrier 40–50 cm deep with the rim just above ground: you get the blue foliage without it taking over everything.

Lyme grass: when to prune it?

Pruning months: February–March and August.

When: Cut the old foliage back in late February or March, before the new leaves appear. Spent flower spikes can be removed in August.

How:

• Cut all leaves and old spikes back to 5–10 cm above the ground.
• Remove any runners that have popped up outside their space at the same time.
• In August, cut faded flower spikes off at the base if they look untidy.

Caution: Cutting back does not stop it spreading: only a root barrier or a pot keeps the rhizomes in place.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or September, chop off a piece of rhizome with a few shoots and replant it straight away. It almost always takes.

Runners

Pot up runners pulled out with a piece of rhizome, to give away or use elsewhere.

Lyme grass: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy to about −30 °C: no protection is needed in Belgium.
• In winter the leaves turn pale and ragged; leave them until late February, they protect the base.
• Wet feet are more dangerous than frost: make sure the soil drains well.
• In a pot it can stay outside; stand the pot on feet so water can drain away.

Diseases and pests

• Spreading: Runners pop up far from the clump, among other plants or under paving. Use a root barrier or pot and chop off runners every spring.
• Green, floppy leaves: Too much shade, water or fertiliser. Move it to a sunny, poor spot.
• Collapsing spikes: After rain or on rich soil. Do not feed, and cut the spikes off if they get in the way.
• Rot: Losses in winter on heavy, wet soil. Improve drainage or move it to sand or gravel.

Through the year

• February: Cut old foliage back to 5–10 cm.
• March: Cut back if not done yet. Plant and divide. Chop off runners.
• April: Plant and divide. Check the root barrier.
• May: Plant. New blue foliage. Water young plants in dry spells.
• June: Flowering begins. Pull out runners outside their space.
• July: Flowering. No water or feeding needed.
• August: Cut off spent flower spikes.
• September: Plant and divide.
• October: Plant. Chop off the last runners.
• December: Rest. Leave the foliage standing.

Did you know?

• Together with marram grass, lyme grass stabilises dunes: its rhizomes hold the sand together and the plant grows back up when it is buried by blown sand.
• It is related to wheat and barley. In Iceland its grain was once harvested and eaten as a cereal.
• The blue colour comes from a waxy coating on the leaves, which helps the plant save water.