Big bluestem

Big bluestem: how do you recognise it?

Habit

Upright, clump-forming plant with foliage to 80–100 cm and flower stems to 1.8 m; about 60 cm wide.

Leaves

Long and narrow, blue-green, sometimes edged purple; coppery red to reddish brown in autumn.

Flowers

In August–September, usually three finger-like spikes at the top of the stems, purplish red with yellow stamens.

Stems

Sturdy, blue-green to purplish; they mostly stay upright through winter.

Roots

Very deep and dense, more than 2 m deep on the prairie: that is why the grass is so drought-tolerant.

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

Why grow it?

• An impressive, tall grass that takes up little ground: up to 1.8 m tall, but only 60 cm wide.
• Beautiful autumn colour in copper and reddish brown, which lasts into winter.
• The seeds are winter food for birds, and insects overwinter in the clump.
• Very drought-tolerant thanks to its deep roots, and fully hardy.
• A perfect fit for a prairie-style planting among late-flowering perennials.

Big bluestem: where does it grow best?

• Full sun: in shade it flops and colours less well.
• Any well-drained soil: sand, loam or clay, acid to chalky; poor soil gives sturdier stems.
• Dry to normally moist; once established it tolerates long droughts.
• Allow 60 cm per plant; in a prairie-style planting, set them in small groups among perennials.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry or normal

Size

1.8 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Purple coneflower: Flowers in summer and stands out nicely against the blue-green leaves.
• Gayfeather: Purple spikes, and like the grass, a prairie native.
• Switchgrass: A second prairie grass, shorter and with fine, airy panicles.
• Michaelmas daisy: Flowers in September–October among the copper-coloured stems.
• Black-eyed Susan: Yellow flowers with a dark centre in late summer.

Big bluestem: when and how to plant it?

Plant in April–May.

1. Plant in April–May: this warmth-loving grass only starts growing once the soil warms up.
2. Dig a hole twice as wide as the pot and loosen the subsoil well for the deep roots.
3. Set the clump at the same depth as it was in the pot and firm the soil.
4. Space plants about 60 cm apart; it looks best in a group of three to five.
5. Water in well straight away, and during dry spells in the first season.
6. Do not add compost or fertiliser to the planting hole: on rich soil the stems become floppy.

Care

Watering

Only in the first year during dry spells; after that, watering is no longer needed.

Feeding

Do not: rich soil and fertiliser give long, floppy stems that fall over.

Patience in spring

The grass is late to start, often not until May. So do not dig it up if you see nothing yet in April.

Winter display

Leave the whole grass standing through winter: it looks lovely with frost and birds eat the seeds.

Renewing

If the clump becomes bare in the middle after a number of years, divide it in May.

Tip: Plant it at the back of the border or as a free-standing group, where the low autumn sun shines through the coppery stems. Wait until March to cut it back.

Big bluestem: when to prune it?

Pruning months: March.

When: In March, before the new leaves appear. Leave the grass standing all winter.

How:

• Cut all old stems and leaves back to 10–15 cm above the ground.
• Tie the stems together with string first: you can then cut them in one go with hedge shears, with less mess.
• Use the clippings as mulch between other plants or put them on the compost heap.

Caution: Do not cut back in autumn: you lose the autumn and winter colour, and birds and insects lose food and shelter.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In May, when the grass starts growing: cut pieces from the edge with a sharp spade, each with a few shoots and roots, and replant them straight away.

Seed

Sow in spring in warm weather in a seed tray; seedlings grow slowly in their first year. Cultivars do not come true from seed.

Big bluestem: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection needed.
• Leave stems and seed heads standing: birds eat the seeds and insects overwinter in the clump.
• Wet snow can flatten the stems; simply cut them back in March.
• This deep-rooted grass grows less well in a pot; choose a large, deep pot on pot feet.

Diseases and pests

• Flopping: On rich, moist soil or in shade the stems fall apart. Plant in a sunny, poor spot and do not feed.
• Late start: In April the clump looks dead. That is normal: this grass only starts growing in warm weather, often in May.
• Rust: Orange-brown spots on the leaves, especially in damp summers. Rarely serious: give it sun and space for air to circulate, and clear old leaves in March.
• Bare centre: After a number of years the middle of the clump dies. Divide it in May and replant the vigorous outer pieces.

Through the year

• January: Leave the grass standing. Birds eat the seeds.
• March: Cut everything back to 10–15 cm.
• April: Plant. No growth yet: be patient.
• May: Plant. New shoots appear. Divide old clumps.
• June: Growth. Water young plants in dry spells.
• July: Tall, blue-green stems.
• August: Flowering with purplish-red spikes.
• September: Flowering. First autumn colour.
• October: Coppery red to reddish-brown autumn colour.
• November: Leave standing for birds and insects.
• December: Winter silhouette in the border.

Good for wildlife

Birds

Berries, seeds or insects as food, or a place to nest.

Did you know?

• This grass once covered vast areas of tallgrass prairie in North America, together with a few other species.
• The nickname ‘turkeyfoot’ comes from the three spikes at the top of the stem, which look like a bird’s foot.
• It is a so-called warm-season grass: it grows mainly in warm weather, which is why it starts so late in spring.