Bitter panicgrass

Bitter panicgrass: how do you recognise it?

Habit

Upright, loose clump about 1.2 m tall and 60–80 cm wide, slowly spreading by short rhizomes.

Foliage

Stiff, narrow and straight, steel-blue to blue-grey; straw-yellow to golden brown in autumn.

Flower

Airy, open panicles of small spikelets above the foliage, from August to October.

Season

A warm-season grass: it starts late in spring (often not until May) and grows most in summer.

Roots

Deep and branching, with rhizomes: the plant sits firmly in sand and gets through dry spells.

Flowering: August–October · Plants: April–May · Pruning: March

Why grow it?

• Steel-blue foliage that stands out all season and combines well with yellow, purple and pink.
• Tolerates drought, wind, salty air and poor sandy soil: ideal for coastal areas and sunny, dry borders.
• Airy flower panicles from August to October, a late display when many borders are winding down.
• Good structure in winter: the stiff, straw-coloured clumps stand until spring.
• Low maintenance: once established it needs no extra water or feed, and one cut a year is enough.

Bitter panicgrass: where does it grow best?

• Full sun: in shade the foliage turns greener and the clumps open out.
• Well-drained sandy or loamy soil, neutral to chalky. It tolerates poor soil; in rich soil it grows too lush and flops.
• Dry to moderately moist: once established it needs hardly any water. It dislikes cold, wet winters.
• Suits seaside gardens and windy spots, as it tolerates salty air.
• Allow 60–80 cm between plants.

Light

Sun

Soil type

Sand or loam

Acidity

Neutral or chalky

Moisture

Dry or normal

Size

1.2 m tall, 0.8 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Coneflower (Echinacea): Pink flowers above the blue foliage, in the same sunny, well-drained soil.
• Stonecrop (Sedum): Low, fleshy plants with pink late-summer flowers that like the same dry sun.
• Sage (Salvia): Purple flower spikes in early summer, before the grass flowers.
• Sea holly (Eryngium): Silvery-blue thistles that go well with the steel-blue leaves.
• Rudbeckia: Yellow flowers in late summer: a lovely contrast with the blue foliage.

Bitter panicgrass: when and how to plant it?

Plant in April–May.

1. Plant in April or May, once the soil has warmed up: this warm-season grass establishes best then.
2. Dig a hole twice as wide as the root ball. On heavy soil, mix in coarse sand or grit for better drainage.
3. Set the plant at the same depth as in its pot and firm the soil well.
4. Leave 60–80 cm between plants.
5. Water in thoroughly straight away, then weekly in dry weather during the first year.
6. Cover the soil with a thin layer of gravel or compost, keeping it clear of the base of the clump.

Care

Water

Only in the first year during dry spells. After that it looks after itself. In a pot, water when the top layer is dry.

Feeding

Not needed: it looks best on poor soil. Too much feed gives soft, green foliage.

Spring growth

It starts late, often not until May. That is normal, so do not clear the clump too early.

Support

Usually not needed. If the clump splits open it is in too much shade or soil that is too rich: move or divide it.

Tidying

Leave the clumps standing over winter and cut them back in March.

Dividing

If the clump gets too big or bare in the centre, divide it in May.

Tip: Wait until May before writing the plant off: this warm-season grass starts late. Give it full sun and no feed, and the foliage stays blue and the clump stays upright.

Bitter panicgrass: when to prune it?

Pruning months: March.

When: In March, just before the new shoots start to grow.

How:

• Cut all stems and leaves back to about 10–15 cm above the ground.
• Tie the clump together with string first: this makes clearing up easy.
• Wear gloves, as the leaf edges of grasses can be sharp.
• The cuttings can go on the compost heap.

Caution: Do not cut in autumn: the old leaves protect the heart of the plant from wet and frost.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In May–June, when growth gets going: split a clump with a sharp spade into pieces, each with roots and shoots, and replant straight away. Keep them moist until they take.

Detaching offsets

In May, cut away a young rooted shoot at the edge of the clump and plant it separately.

Bitter panicgrass: how does it get through the winter?

Hardy to −25 °C.

• Hardy to about −25 °C: in Belgium no protection is needed, as long as the soil drains well.
• Cold, wet winters are more dangerous than frost. On heavy soil, plant on a slight mound and leave the old leaves in place until March as a cover.
• In a pot: stand it against a sheltered wall and wrap the pot in hessian or bubble wrap.

Diseases and pests

• Open, flopping clump: Caused by shade or soil that is too rich. Move to full sun, do not feed, and divide the clump.
• Rotting in winter: On cold, wet clay the clump can rot away. Mix sand or grit into the soil, or plant on a mound.
• No growth in April: The plant is not dead: warm-season grasses do not start until May. Be patient.
• Rust: Orange-brown spots on the leaves after long, damp spells. Usually harmless: cut off affected leaves in March and leave enough space between plants.

Through the year

• March: Cut all clumps back to 10–15 cm.
• April: Plant or move. Nothing to see yet: the grass starts late.
• May: Plant or divide. First shoots appear. Mulch with gravel or compost.
• June: Strong growth. In the first year water weekly in dry weather.
• July: The blue foliage is at its best.
• August: Flowering begins, with airy panicles.
• September: In flower. The foliage slowly changes colour.
• October: Late flowers and autumn colour.
• November: Leave the clumps standing: they protect the heart of the plant.
• December: Resting. The straw-coloured clumps decorate the garden.

Did you know?

• In the wild it grows on beaches and dunes along the east coast and Gulf coast of the United States, where its rhizomes hold the sand in place.
• The species name amarum is Latin for ‘bitter’.
• It belongs to the warm-season grasses, which grow mainly in summer and start late in spring.