How big does Blue oat grass grow?

About 90 cm × 75 cm after ten years (height × width). Its ultimate size is 0.6–1.5 m × 0.6–1 m.

What soil does Blue oat grass grow in?

It tolerates these soils: average garden soil, sandy, calcareous.

Is Blue oat grass hardy?

Hardy down to -34 °C (USDA zone 4, RHS H7). It gets through winter in every part of the country.

When does Blue oat grass flower?

Flowering: June–August, yellow.

How much water does Blue oat grass need?

Water need: low. Drought tolerance: high.

Blue oat grass

Helictotrichon sempervirens

Blue oat grass (Helictotrichon sempervirens) is an ornamental grass that reaches 90 cm × 75 cm after ten years. Light: full sun. Hardy down to -34 °C. Drought tolerance: high. Sold in local shops from about €7.90.

Illustration of Blue oat grass — An illustration of the typical shape of the mature plant, not a photo.

What it's good for, and what it isn't

An ornamental grass that forms a steel-blue, porcupine-like dome which keeps its leaves through winter, with tall arching flower stems that ripen to straw yellow in early summer. It belongs in a sunny, dry, well-drained spot such as a gravel bed, rock garden or modern border, and looks good alone or in small groups. Do not cut it back hard: in spring just comb out the dead leaves by hand and remove the old flower stems.

Watch out for

In heavy, wet, poorly drained soil the crown rots, especially in winter. In humid, warm summers and in crowded, airless spots rust can appear on the leaves, and in shade it is prone to other leaf diseases and turns greener. It copes poorly with prolonged muggy heat, when the clump can thin out. In a hard winter part of the foliage dies and needs cleaning out in spring. After a few years the centre of the clump may go bare, and it is then worth renewing by division in spring.

Key facts

Light: Full sun
Water need: Low
Care: Low
Size after 10 years: 90 cm × 75 cm
Hardiness: down to -34 °C
Foliage: Semi-evergreen
Flowering: J F M A M J J A S O N D June–August, yellow

Group	Ornamental grass
Light	Full sun
Size after 10 years	90 cm × 75 cm
Ultimate size	0.6–1.5 m × 0.6–1 m
Hardiness	down to -34 °C (USDA 4, RHS H7)
Soil	Average garden soil, Sandy, Calcareous
Foliage	Semi-evergreen
Flowering	June–August, yellow
Water need	Low
Drought tolerance	High
Maintenance	Low
Root aggressiveness	Low
Suckering	no data
Spreading	Low
Distance from buildings	no data
Distance from paving	no data
Litter	not typical
Planting distance	60 cm
For dogs	no data
For cats	no data
For children	no data
Typical price	from about €7.90

Toxicity data is for information only. If your pet or child has eaten a plant, contact a vet or a doctor.

Sizes and prices available

The same plant is sold as a small pot and as a specimen several metres tall, and the price follows. Prices are rounded and for guidance only.

Size	Typical price
size not stated	approx. €7.90

Frequently asked questions

Data updated: October 8, 2026 · How our data is made

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