Mexican feather grass

Sun

Full sun; tolerates light shade but grows less densely.

Water

Low once established; water young plants during dry spells. Avoid frequent watering and persistently wet soil.

Soil

Well-drained, preferably lean soil; sandy, gravelly or stony ground suits it. Heavy soil that stays wet in winter can kill it.

Height

1.5-2 ft (0.45-0.6 m)

Spread

1-2 ft (0.3-0.6 m)

Flowers

Late spring through summer; fine greenish flower heads mature to silvery straw and pale gold.

Foliage

Very narrow, flexible green leaves form a fountain-shaped tussock, becoming straw-coloured with age. Evergreen in mild climates and partly evergreen or dormant after harder frost.

Growth

Moderate to fast; seedlings can reach flowering size quickly in favourable conditions.

Care needed

Medium

• Check local invasive-plant rules before buying or planting; choose an alternative where it threatens nearby habitats.
• Water during establishment, then only during prolonged drought; let the soil dry between waterings.
• Avoid routine feeding, which encourages soft, floppy growth.
• Keep the crown clear of damp organic mulch; a light gravel mulch suits dry sites.
• Remove flower heads before seed matures and pull seedlings promptly; deadheading reduces spread but cannot guarantee containment.

Pruning. In late winter or early spring, wear gloves and gently comb out loose dead leaves without pulling up the crown. Avoid routinely shearing green tussocks; if foliage is badly winter-damaged, trim it to about 4-6 in (10-15 cm) before new growth develops.

Late winter

Check for winter-wet damage and gently remove loose dead foliage.

Spring

Where planting is permitted and ecologically appropriate, plant into free-draining soil after severe frost has passed.

Late spring

Pull unwanted seedlings while small, including those in paving joints and gravel.

Summer

Remove developing flower heads before seeds ripen; bag seed-bearing material rather than putting it in home compost.

Late summer

Check for replacement flower heads and remove them before they shed seed.

Autumn

Clear fallen debris away from crowns and check that winter rain can drain freely.

• In regions where it is appropriate to grow, repeat small groups through gravel planting to create a soft, moving layer.
• Pair with upright salvias and coneflowers for contrast between airy grass and solid flower shapes.
• Use against dark walls or evergreen shrubs, where the pale seed heads catch low sunlight.
• Plant beside broad-leaved sedums or bold succulents to contrast fine and substantial foliage.

Garden styles it suits: Dry gravel garden, Mediterranean, New perennial (prairie), Modern Mediterranean, Desert / xeriscape and Sensory garden.

Plant it with: Lavender, Russian sage, Purple coneflower, Yarrow, Autumn stonecrop and Upright salvias.

Wildlife: Clumps provide cover for small invertebrates, and birds may collect the fine material for nests. Flowers are wind-pollinated rather than a nectar source; invasive populations can displace more valuable native habitat.

• Excessive self-seeding: remove flower heads before ripening and pull seedlings promptly; replace the plant where escape into surrounding land is likely.
• Crown or root rot in wet soil: improve drainage or move to a raised, gritty bed; discard plants with rotted crowns.
• Floppy, lush growth: reduce watering and stop feeding; move plants into full sun if shaded.
• Winter browning or death: shelter from cold, drying winds and avoid winter-wet sites; replace dead clumps only where the species is suitable to grow.

Not known to be poisonous to cats, dogs, horses or people. However, the sharp, awned seeds can lodge in fur, skin, eyes or mouths and cause painful injuries or infection; this is a physical hazard rather than poisoning. Seek veterinary advice if seeds become embedded.

Where it spreads. An aggressive, wind-dispersed self-seeder in suitable climates. It is invasive in California and parts of Australia and New Zealand, where it can escape into grassland and other open habitats. Australia prohibits its importation and has state and territory restrictions on its keeping, sale and movement; it is also banned from sale and distribution under New Zealand's National Pest Plant Accord.

• Giant feather grass (Stipa gigantea)

  Produces much taller, widely spaced stems carrying large, oat-like golden flowers above a basal clump; Mexican feather grass has low, fine, silky flower heads.

• Blue fescue (Festuca glauca)

  Usually forms shorter, stiffer blue-grey mounds with relatively upright flower stems, rather than soft green tussocks with flowing, hairlike foliage.

The species name tenuissima means 'very slender', referring to its exceptionally fine foliage, while Mexican feather grass refers to part of its native range and its feathery appearance.

Propagation. Usually grown from seed, but do not propagate where prohibited or where seedlings could escape into natural areas. Where appropriate, sow in spring in a well-drained medium; unwanted self-sown seedlings are usually plentiful.

Accepted botanical name

Nassella tenuissima

In the US and Canada

Native in the lower 48 states.

Native range

Argentina Northeast, Argentina Northwest, Argentina South, Colorado, Mexico Central, Mexico Gulf, Mexico Northeast, Mexico Southwest, New Mexico and Texas.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.