False oat-grass

How to recognise it

Habit

Loose, tall tuft of 50–150 cm with upright stems; no long runners.

Leaf

Flat, fresh green to grey-green, 4–10 mm wide, slightly rough and sometimes sparsely hairy; the ligule is short, 1–3 mm.

Flower

Loose, shiny panicle of 10–30 cm, narrow at first and spreading wide in flower, from June to August. Each spikelet has two flowers: the lower, male flower carries a long, bent and twisted awn; the upper one has at most a short awn.

Stem

Smooth stems with mostly hairless nodes; in the bulbous form (onion couch) the lowest internodes are swollen into a string of small bulbs.

Fruit/Seed

The seed ripens in July–August; the panicle then turns straw yellow and stays standing for a long time.

Confusion with

Yellow oat-grass has a smaller, golden-yellow, shiny panicle and spikelets with usually three flowers. Wild oat is annual, with much larger, drooping spikelets. Yorkshire fog is softly hairy and has no long awns.

Flowering: June–August · Pruning: June and September

Why grow it?

• It gives its name to false oat-grass meadows: flower-rich verges and hay meadows that are among the most species-rich grasslands in Belgium.
• The tall, shiny panicles move beautifully in the wind and give a flower meadow height and structure.
• Caterpillars of grassland butterflies, such as the meadow brown, and many grasshoppers feed on broad-leaved grasses like false oat-grass.
• The tall tufts and hollow stems shelter insects and spiders all year round, winter included.
• In late summer, seed-eaters such as finches and sparrows feed on the seed.
• A tough, drought-tolerant grass whose roots hold banks and dykes together.

False oat-grass: where does it grow best?

• In the wild: road verges, dykes, railway banks, hay meadows, rough grassland and woodland edges.
• Full sun to light partial shade.
• Moderately dry to moist, fairly fertile soil: loam, clay, sandy loam and chalky sand. It does not tolerate prolonged waterlogging.
• In the garden: in a flower meadow on loam or clay, on a bank or in a rough strip along a hedge.
• It dislikes frequent mowing: in a lawn it soon disappears.

Goes well with

• Oxeye daisy: White flowers in June among the shiny panicles.
• Knapweed: Purple flowers for bumblebees and butterflies in July–August.
• Field scabious: Lilac flower heads, much loved by solitary bees.
• Hedge bedstraw: Clouds of small, white, scented flowers on the same verges.
• Yellow rattle: A semi-parasite of grasses that holds false oat-grass back and makes room for flowers.

False oat-grass: when and how to plant it?

1. It usually turns up by itself on a verge or in a garden that is mown less often; there is then no need to sow it.
2. To create a flower-rich meadow on loam or clay, choose a mix of native grasses and wild flowers that includes false oat-grass, of native origin.
3. Sow in September–October so that the wild flowers in the mix get their cold period; March–April also works.
4. Prepare a fine, weed-free seedbed, sow thinly, rake the seed in lightly and firm or roll it.
5. Keep the seedbed moist until germination, after 1–3 weeks.
6. Never take turves or plants from verges or nature reserves: verges are valuable habitat too.

Care

Watering

Not needed, even in dry summers.

Feeding

Never: fertiliser turns it into tall, grassy rough ground without flowers.

Mowing

Mow twice a year, in mid-June and in September, and remove the cuttings. This is the classic management of a flower-rich false oat-grass verge.

Spreading

On rich soil it can become dominant. Then mow earlier, in late May, for a few years and sow yellow rattle to hold the grass back.

Self-seeding

Leave the hay lying for two to three days before removing it, so the seed of grasses and flowers can drop.

Tip: Want a flowery verge? Mow twice a year with a scythe or reciprocating-blade mower and always remove the cuttings: within a few years, rough grass with false oat-grass turns into a colourful hay-meadow verge.

Pruning and mowing

Pruning months: June and September.

When: Mid-June and again in September, like a hay meadow.

How:

• Mow at 5–10 cm with a scythe, brushcutter or reciprocating-blade mower; a flail mower kills far more insects.
• Let the hay dry for a few days, then remove it.
• Leave 10–20 % uncut each time, in a different place every time.
• In autumn, leave a strip standing until spring: hollow stems and tufts are winter quarters for insects.

Caution: Flail mowing and leaving the cuttings make the soil richer: the flowers disappear and only rough grass and nettles remain.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Seed

Ripens in July–August and self-seeds readily on bare soil; sow preferably in autumn.

Division

In spring or autumn dig up a tuft and split it with a spade.

False oat-grass: how does it get through the winter?

Hardy to −30 °C.

• The tufts stay partly green; the old stems turn straw yellow and remain standing for a long time.
• Fully hardy, to about −30 °C.
• Insects and spiders overwinter in the hollow stems and dense tufts.

Diseases and pests

• Too dominant: On fertile soil it crowds out flowers. Two cuts a year with removal of the cuttings, and sowing yellow rattle, help.
• Flopping: After rain or on soil that is too rich, the tall stems fall over. Lowering fertility helps, as does a first cut in mid-June.
• Onion couch: This form with small bulbs at the base is a nuisance in vegetable plots and borders: every bulb regrows. Dig out the tufts with all their bulbs.
• Hay fever: Its pollen can cause hay fever in sensitive people in June–July.

Through the year

• March: Dividing tufts or sowing a meadow is possible.
• May: Rapid growth; the panicles emerge.
• June: Flowering starts with shiny panicles. First cut in mid-June.
• July: Flowering on uncut strips; seed ripens.
• August: Late flowers and regrowth after mowing.
• September: Second cut, remove the hay; leave a strip standing.
• October: Best month to sow a flower meadow.
• December: Dormant; insects overwinter in tufts and stems.

Did you know?

• Arrhenatherum comes from the Greek arrhen (male) and ather (awn): only the male flower in each spikelet carries a long awn.
• In the bulbous form, a few small bulbs sit in a row at the base of the stem, like a little string of pearls.
• False oat-grass used to be sown as a hay grass; in English it was also called French rye-grass.