Plant problems

Why Are My Nardus Leaves Curling?

Q: Why is nardus stricta called mat grass?

Nardus stricta is called mat grass because of its growth form in its natural upland grassland habitat: the dense, wiry, low-growing, interlocked tufts of stiff, bristle-like grey-green leaves form a continuous, close, mat-like sward across the ground surface that is characteristic of impoverished, acid, upland grassland in the UK highlands, moorlands, and mountains. In the upland grassland habitats where nardus is dominant — particularly on peaty or thin mineral acid soils that are too impoverished for more productive grass species such as bent grasses or fescues — the tightly packed, stiff leaves form a very dense, low, wiry texture that gives the impression of a mat laid across the ground surface, particularly when seen across an expanse of moorland or mountain grassland. The alternative common name 'mountain grass' refers to its abundance in the upland and montane zones of Scotland, Wales, and northern England, where it is one of the most extensive and characteristic grassland types. In the UK upland farming context, nardus stricta grassland is generally regarded as low-quality rough grazing, as the stiff, wiry leaves are less palatable and nutritious to sheep and cattle than the more productive bent-fescue swards that can develop on the same sites when grazing pressure is managed; however, nardus-dominated upland grassland has significant value for some upland wildlife species, particularly for the Daubenton's bat, the mountain ringlet butterfly (one of the few upland butterfly specialists dependent on nardus grassland), and a range of upland birds. The Latin name stricta means 'upright' or 'erect', referring to the stiffly erect, bristle-like leaves.

Q: Is nardus stricta suitable for a UK garden?

Nardus stricta (mat grass) is a very specialist plant with narrow habitat requirements that make it generally unsuitable for most UK garden contexts; it is designed by evolution for the most nutrient-poor, acid, open, windswept conditions of UK upland and mountain grassland and does not perform well in the conditions of most UK gardens, which are typically too warm, too fertile, too sheltered, and (in the south) too dry in summer for nardus to compete successfully with more productive, fertility-tolerant grassland species. In a typical UK garden border, nardus would be quickly outcompeted by common grassland and garden weed species. However, in a specialist acid garden or heathland garden context on naturally poor, acid soil (or a specially prepared area of acidic, low-fertility substrate), nardus stricta can be a genuinely interesting and authentic native grassland component: the dense, wiry, grey-green tufts with the stiff bristle-like leaves are texturally quite distinctive compared to any other ornamental grass in cultivation. The most natural and practical use of nardus in a UK garden or managed landscape context is in an acid heathland or upland wildflower grassland restoration project, where the acid, impoverished soil conditions match nardus's natural requirements and where it can develop the characteristic dense mat-like sward that makes it so recognisable in its native upland habitat. Nardus stricta seed is available from a small number of UK native wildflower seed suppliers who source it for grassland and heathland restoration projects; it is not typically sold as an ornamental grass from mainstream garden centres.

Q: Is nardus stricta native to the UK?

Yes, Nardus stricta (mat grass, matgrass) is native to the UK and is one of the most abundant and ecologically significant upland grassland grasses in the British Isles; it is the dominant grass of vast areas of acid upland grassland, moorland fringe, mountain grassland, and blanket bog margins in Scotland, Wales, the north of England (Yorkshire Dales, North Pennines, Lake District), the south-west uplands (Exmoor, Dartmoor), and parts of upland Ireland. In Scotland in particular, nardus stricta grassland is one of the most extensive upland grassland communities, covering large areas of the Southern Uplands, the Grampians, and the Scottish Highlands, particularly on deep, peaty, acid soils at elevations above 300 to 400 m. Nardus stricta grassland is a recognised National Vegetation Classification (NVC) plant community (CG10 and several sub-communities within the mesotrophic and acid grassland and heath NVC groups) and is also listed as a UK Biodiversity Action Plan (BAP) priority habitat in the upland grasslands section, reflecting its ecological significance as a habitat for a range of upland wildlife species including the mountain ringlet butterfly (Erebia epiphron, a Red List species in the UK), various upland bird species, and specialist upland invertebrates. It is classified as an Ancient Grassland indicator in the appropriate NVC community contexts, as long-established, unimproved, unfertilised nardus grassland typically has a distinct associated flora of acid grassland plants (heath bedstraw, tormentil, wavy hair-grass, deer grass) that takes centuries to develop. Nardus stricta is not, however, regarded as a desirable component of UK lowland meadows or agricultural grassland, where it is associated with impoverishment and overgrazing rather than biodiversity.

Nardus stricta (mat grass) is a native UK grass of acid upland moorland and mountain grassland, forming dense, wiry, low-growing tufts with stiff, bristle-like grey-green leaves. A specialist of impoverished, acid, low-fertility conditions, it is quickly outcompeted in fertile garden soils. Yellowing and curl indicate either too much fertility or waterlogging.

Too much soil fertility

Nardus is an extreme specialist of nutrient-poor, acid soils with very low phosphorus and nitrogen; in moderately or highly fertile garden soil it is outcompeted by more vigorous, fertility-tolerant species and gradually loses its characteristic dense, wiry-tufted form. In a garden border that has been amended with compost or fertiliser, nardus will not maintain the compact character seen in its native habitat.

What to do

For a garden context, provide only acid, low-fertility substrate; do not add compost, fertiliser, or lime. A raised bed or dedicated acid area prepared with lime-free grit, acid sand, and peaty compost provides a controlled low-fertility environment. Do not top-dress with any nutrient-rich mulch. If the wider garden soil is too fertile, nardus is not the right plant; consider acid-tolerant but slightly more adaptable alternatives such as Deschampsia flexuosa (wavy hair-grass) or Molinia caerulea (purple moor-grass).

Waterlogging

Nardus tolerates seasonally moist to moderately wet acid upland soils in its native habitat, but prolonged, persistently anaerobic waterlogging in a garden context causes the leaves to yellow and the wiry clump to open up and lose its characteristic density. In heavy clay or a compacted garden soil that pools water through winter, nardus declines even if other conditions are suitable.

What to do

Ensure basic drainage; nardus tolerates seasonal wetness but not persistent winter waterlogging. In a heavy or compacted garden soil, incorporate grit or coarse acid sand to improve drainage. In an acid heathland restoration context, nardus can tolerate seasonally high water tables typical of moorland fringe habitats, but not bog-like permanently saturated conditions.

Wrong growing conditions

Nardus is a grass of cool, open, acid, impoverished upland Britain; in a warm, sheltered, fertile, lowland garden position it is gradually displaced by more competitive species. It is most suited to northern and western UK gardens with naturally acid, poor soil and open, exposed conditions. In a warm, sheltered south-facing border in the English lowlands, nardus cannot maintain the form seen in its native Scottish or Welsh mountain habitat.

What to do

In a lowland UK garden, use nardus only in a specialist acid heathland or upland wildflower grassland restoration project with naturally or deliberately impoverished acid soil. For a more widely adaptable acid-soil ornamental grass in a garden border, substitute Deschampsia flexuosa (wavy hair-grass, which has an attractive light-catching quality and is more adaptable to garden cultivation) or Festuca ovina (sheep's fescue, a fine-leaved acid grassland grass that tolerates a wider range of garden conditions).

Frequently asked questions

Why are my nardus leaves curling?

Nardus leaves curl and yellow most commonly because of too much soil fertility (extreme specialist of nutrient-poor, acid, impoverished soils; outcompeted quickly in fertile garden soil; no compost, no fertiliser, no lime; use only acid, low-fertility substrate), waterlogging in persistently anaerobic conditions (tolerates seasonal wetness but not permanent winter waterlogging; improve drainage with grit or acid sand), or wrong growing conditions overall (cool, open, acid, upland UK specialist; lowland warm fertile gardens are not suitable; substitute Deschampsia flexuosa or Festuca ovina for garden use).

Why is nardus stricta called mat grass?

Because the dense, wiry, low-growing, interlocked tufts of stiff, bristle-like grey-green leaves form a continuous, close, mat-like sward across the ground in upland grassland. Dominant over vast areas of acid upland moorland in Scotland, Wales, and northern England at elevations above 300 to 400 m. The alternative name 'mountain grass' reflects its abundance in the upland and montane zone. The Latin epithet stricta means 'erect', referring to the stiffly upright bristle-like leaves.

Is nardus stricta suitable for a UK garden?

Generally unsuitable for most UK garden conditions because it needs the most nutrient-poor, acid, open, impoverished conditions; it is quickly outcompeted by common garden species in fertile soil. Best suited to a specialist acid heathland or upland wildflower grassland restoration project with naturally or deliberately impoverished acid soil. Nardus seed is available from UK native wildflower seed suppliers for grassland restoration use. For an acid garden border, Deschampsia flexuosa is a more adaptable alternative with similar wiry, light-catching character.

Is nardus stricta native to the UK?

Yes; one of the most abundant upland grassland grasses in the British Isles, dominant over vast areas of acid upland moorland, mountain grassland, and blanket bog margins in Scotland, Wales, and northern England. A recognised NVC plant community and UK Biodiversity Action Plan priority habitat. An ancient grassland indicator in appropriate NVC community contexts. Associated flora in established nardus grassland includes heath bedstraw, tormentil, wavy hair-grass, and deer grass. Host plant for the mountain ringlet butterfly (Erebia epiphron), a UK Red List species.