What hardiness zones is Helictotrichon sempervirens suitable for?

Helictotrichon sempervirens is suitable for USDA hardiness zones 4, 5, 6, 7, 8, 9.

What are the sun requirements for Helictotrichon sempervirens?

Helictotrichon sempervirens requires Full Sun.

How much water does Helictotrichon sempervirens need?

Helictotrichon sempervirens has Low water needs.

Grasses & Grass-like

Helictotrichon sempervirens

blue oat grass

Poaceae

Western Mediterranean, including southern France, northern Italy, and the Atlas Mountains of northwestern Africa

At a Glance

TypeGrass

HabitMounding

FoliageEvergreen

Height24-30 inches (60-76 cm)

Width24-30 inches (60-76 cm)

Maturity3 years

Growing Zones

USDA Hardiness Zones

4 - 9

Zone 4

Zone 5

Zone 6

Zone 7

Zone 8

Zone 9

These zones indicate the coldest temperatures this plant can typically survive.

Frost Tolerancehardy

Key Features

Deer Resistant

Drought Tolerant

Container Friendly

Maintenancemoderate

Overview

A cool-season, clump-forming perennial grass reaching 24–30 inches (60–76 cm) tall with a similar spread, excluding flower stalks. Leaves are narrow, 12–18 inches (30–46 cm) long and approximately 0.25 inches (6 mm) wide, blue-gray with a waxy bloom on both surfaces. Foliage is stiff and arching, forming a dense, fountain-shaped mound. Leaf tips taper to a sharp point; margins are finely scabrous. In late spring to early summer, wiry flowering culms rise 36–48 inches (90–122 cm) above the foliage, bearing loose, one-sided panicles of oat-like spikelets that emerge tan to straw-colored and dry to a pale buff. Spikelets are approximately 0.5 inches (12 mm) long. Growth rate is slow to moderate; plants reach mature size in 2–3 years from a gallon container. The foliage is evergreen in zones 7–9, semi-evergreen in zones 5–6, and may brown at tips during cold, wet winters. Clumps tend to die out in the center after 4–6 years in humid climates or heavy soils. Inner foliage turns brown over winter and requires annual removal. Does not spread by runners or rhizomes.

Native Range

Native to the western Mediterranean region, including southern France, northern Italy, and the Atlas Mountains of northwestern Africa. Found on rocky, calcareous slopes and dry grasslands at elevations of 1,000–5,000 feet (300–1,500 m).

Suggested Uses

Commonly planted as a specimen in rock gardens, gravel gardens, and Mediterranean-style plantings at 24–30 inch (60–76 cm) spacing. Used in mass plantings of 3–5 along walkways, in parking strip plantings, and in mixed borders where its blue foliage provides contrast. Grows in containers of at least 5 gallons (19 L) with a fast-draining mineral-based mix; container plants may require more frequent replacement due to crown dieback.

How to Identify

Distinguished from blue fescue (Festuca glauca) by larger overall size—24–30 inches (60–76 cm) tall versus 8–12 inches (20–30 cm)—and wider leaf blades approximately 0.25 inches (6 mm) across. Leaf blades are flat to slightly inrolled, stiff, and sharply pointed, with a consistent blue-gray color on both surfaces due to a heavy waxy bloom. Flower panicles are one-sided, loose, and oat-like, borne on slender culms well above the foliage mound, unlike the compact flower clusters of fescues.

Appearance

Size & Dimensions

Height2' - 2'6"

Width/Spread2' - 2'6"

Reaches mature size in approximately 3 years

Colors

Flower Colors

tan

straw

Foliage Colors

blue gray

silver blue

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~5 weeks

SpringSummer

Flowers from late May through July in zones 5–7, beginning approximately two weeks earlier in zone 8. Individual panicles persist for 3–4 weeks; the total flowering period spans 4–6 weeks. Flower stalks dry in place and persist through late summer if not removed. Flowering may be reduced in hot, humid climates or in heavy shade.

Detailed Descriptions

Flower Description

Tan to straw-colored

Foliage Description

Blue-gray with heavy waxy bloom on both surfaces

Growing Conditions

Sun Requirements

Full Sun

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 8.0(Neutral)

357912

Soil Types

loamsandchalkrocky

Drainage

well drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Water deeply once per week during the first growing season; established plants require supplemental water only during prolonged drought exceeding 3–4 weeks. Overwatering and poorly drained soils cause root rot and crown dieback. Apply 1–2 inches (2.5–5 cm) of gravel or crusite mulch around the crown; organic mulches hold moisture against the crown and promote rot. Feed lightly in early spring with a balanced granular fertilizer at half the label rate; excessive nitrogen reduces blue coloration. Remove brown inner foliage in late winter or early spring before new growth emerges by combing through the clump with gloved hands or cutting the entire plant back to 3–4 inches (8–10 cm). Plants tend to die out in the center after 4–6 years in humid climates; divide and replant outer portions in early spring when this occurs.

Pruning

Cut back the entire clump to 3–4 inches (8–10 cm) in late February to early March before new growth emerges. Removing old foliage later risks cutting new growth. Flower stalks may be removed after they turn straw-colored in late summer, or left for winter interest and removed during the late-winter cutback. Deadheading does not promote rebloom.

Pruning Schedule

late spring

Maintenance Level

moderate

Container Growing

✓ Suitable for container growing

Minimum container size: 5 gallons

⚠️ Toxicity Warning

Non-toxic