How big does Giant oat grass grow?

About 2 m × 1 m after ten years (height × width). Its ultimate size is 1.5–2.5 m × 0.6–1.2 m.

What soil does Giant oat grass grow in?

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

Is Giant oat grass hardy?

Hardy down to -18 °C (USDA zone 6, RHS H6). In the colder parts of the country (Greater Poland Voivodeship, Holy Cross Voivodeship, Kuyavian-Pomeranian Voivodeship, Lesser Poland Voivodeship, Łódź Voivodeship, Lower Silesian Voivodeship, Lublin Voivodeship, Lubusz Voivodeship, Masovian Voivodeship, Opole Voivodeship, Podlaskie Voivodeship, Pomeranian Voivodeship, Silesian Voivodeship, Subcarpathian Voivodeship, Warmian-Masurian Voivodeship) it may not survive winter without protection.

When does Giant oat grass flower?

Flowering: June–August, purple, yellow.

How much water does Giant oat grass need?

Water need: low. Drought tolerance: high.

Giant oat grass

Stipa gigantea

Giant oat grass (Stipa gigantea) is an ornamental grass that reaches 2 m × 1 m after ten years. Light: full sun. Hardy down to -18 °C. Drought tolerance: high.

Illustration of Giant 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

From a low tussock of grey-green leaves it sends up stems to two metres in early summer, carrying oat-like panicles that open purplish and ripen to gold. The flower heads are see-through, so it works as a specimen even at the front or middle of a border, and the dry panicles stay attractive into winter. It needs full sun and freely draining soil, copes well with drought and resents winter wet; in cold areas plant it in spring.

Watch out for

Hardiness figures disagree: sources give anything from -12 to -29 °C, so it is not fully reliable in the colder, wetter parts of Central Europe. Winter wet does more harm than frost, and plants rot in heavy, waterlogged soil. Give it a loose, gritty, sunny and preferably sheltered south-facing spot, and wait until spring to clear out dead leaves and old stems. It flowers poorly in shade or very rich soil, and strong wind can flatten the tall stems.

Key facts

Light: Full sun
Water need: Low
Care: Low
Size after 10 years: 2 m × 1 m
Hardiness: down to -18 °C
Foliage: Semi-evergreen
Flowering: J F M A M J J A S O N D June–August, purple, yellow

All details

Group	Ornamental grass
Light	Full sun
Size after 10 years	2 m × 1 m
Ultimate size	1.5–2.5 m × 0.6–1.2 m
Hardiness	down to -18 °C (USDA 6, RHS H6)
Soil	Average garden soil, Sandy, Calcareous
Foliage	Semi-evergreen
Flowering	June–August, purple, 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	90 cm
For dogs	no data
For cats	no data
For children	no data
Typical price	no data

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

Frequently asked questions

Data updated: October 17, 2026 · How our data is made

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