Plant problems

Why Are My Parapholis Leaves Curling?

Q: Where does parapholis strigosa grow in the UK?

Parapholis strigosa (hard grass, sea hard grass) is a native UK coastal grass with a strongly coastal distribution, primarily confined to the coastal fringe of England, Wales, and Ireland; it is very rare in Scotland. In the UK, it is found in a characteristic range of coastal habitats: Sea walls and coastal embankments: one of the most typical habitats; parapholis grows in the thin, open, compacted soil on the top and face of coastal sea walls, earth embankments, and flood defences in estuaries and coastal grazing marshes, particularly in south-east England; here it grows alongside other coastal specialists including Puccinellia maritima, Halimione portulacoides, and Armeria maritima. Upper saltmarsh and saltmarsh margins: in the upper, drier, most landward parts of saltmarsh, where periodic flooding is less frequent and the substrate has dried somewhat; parapholis occupies the short, salt-tolerant turf of the upper saltmarsh transition zone. Coastal paths and cliff-tops: on the thin, sun-baked, often slightly saline soil of coastal footpaths, cliff-top grassland, and the disturbed, open, gravelly or stony ground of coastal margins; here it often grows with other salt-tolerant and coastal-adapted annual plants. Dune slacks and sandy coastal ground: in open, sunny, calcareous dune slacks and the drier, more exposed, sandy ground of coastal dune systems; not in the most mobile, shifting dune zone. UK distribution: primarily found along the coast of south-east England (Kent, Essex, Suffolk, Norfolk), south England (Dorset, Hampshire, Isle of Wight, West Sussex, East Sussex), and south-west England (Devon, Cornwall); also present along the Welsh coast and in parts of Ireland; rare in northern England and Scotland. Parapholis incurva (curved hard grass) has a more restricted southern distribution than P. strigosa; it is found primarily on the coasts of south-east England and is rarer and more local.

Q: How is parapholis related to other UK grass genera?

Parapholis is placed in the grass family (Poaceae) in the tribe Poeae and is related to several other UK grass genera with similar ecological preferences for open, disturbed, or specialist habitats: closest relatives and similar genera: Lolium (ryegrasses): Parapholis and Lolium are both members of the broader ryegrass group (tribe Poeae, sometimes subdivided into Poeae sensu stricto and Lolieae); both genera share the feature of producing true spikes with spikelets embedded in the rachis without individual stalks (pedicels); Lolium perenne (perennial ryegrass) and Lolium temulentum (darnel) share this embedded-spikelet arrangement with Parapholis; Lolium spikelets are turned edge-on to the rachis while Parapholis spikelets are face-on. Hainardia cylindrica (Mediterranean ryegrass, one-glumed ryegrass): a Mediterranean grass occasionally found in the UK as a casual introduction; also has a cylindrical, pencil-thin spike with embedded spikelets; extremely similar to Parapholis in gross morphology and superficially almost identical to P. strigosa in the field; distinguished by technical spikelet characters. Catapodium marinum (sea fern grass) and Catapodium rigidum: coastal and dry-ground small annual grasses that grow in similar coastal-fringe habitats to Parapholis strigosa and Parapholis incurva but are distinguished by their branched, fern-like panicle; frequently found growing together with Parapholis at UK coastal sites. Puccinellia (saltmarsh grasses): co-occur with Parapholis in UK coastal habitats but are perennial, produce an open, branching panicle (not a spike), and are more tightly associated with the wetter, more regularly flooded saltmarsh zone.

Q: What other annual grasses are found in UK coastal habitats?

The UK coastal fringe supports a distinctive community of annual and short-lived grass species adapted to the combination of salt spray, thin soils, exposure, and the particular microclimate of the coast: Parapholis strigosa (hard grass): pencil-thin, rigid, cylindrical spike with embedded spikelets; one of the most characteristic and easily identified UK coastal annual grasses; sea walls, upper saltmarsh, coastal paths. Parapholis incurva (curved hard grass): similar to P. strigosa but with more distinctly curved (incurved) spikes; more southern and rarer; south-east England coast. Catapodium marinum (sea fern grass): stiff, one-sided, fern-like, branching panicle; coastal paths, sea walls, cliff-tops; closely associated with P. strigosa at many UK coastal sites. Hordeum marinum (sea barley): a small annual barley of coastal grassland, sea walls, and coastal paths; bristly, barley-like spike; distinguished from H. murinum (wall barley) by its coastal habitat and smaller overall size. Puccinellia fasciculata (Borrer's saltmarsh grass) and Puccinellia rupestris (stiff saltmarsh grass): annual or biennial saltmarsh grasses of drier, upper saltmarsh and coastal turf; closely related to the more widespread perennial saltmarsh grasses. Mibora minima (early sand grass): one of the UK's smallest native grasses; a tiny annual of sandy, coastal, and rocky ground mainly in Wales and south-west England; flowers from February to April. Rostraria cristata (Mediterranean hair grass): a casual introduction occasionally found on coastal and disturbed sandy ground in southern England; graceful, cat's-tail-like flower spike.

Parapholis strigosa (hard grass, sea hard grass) is a small, salt-tolerant, annual coastal grass native to the UK, found on sea walls, upper saltmarsh, coastal paths, and cliff-tops, particularly in south and south-east England. Distinguished by its pencil-thin, rigid, cylindrical spike with spikelets embedded directly in the rachis. Leaves curl from drought and heat in thin coastal soils, or the natural annual die-back after seed set in July to August.

Drought in thin coastal soils

Despite growing in sun-baked, thin, often saline coastal substrates, parapholis has a fine, shallow annual root system; in a particularly hot and dry UK summer, the naturally narrow leaves roll more tightly, the tips brown, and the plant ripens and dies earlier than in a year with more moderate temperatures and some rainfall. Its natural coastal salt-spray exposure and thin-soil habitat mean it has some innate drought tolerance, but extended heat waves push it beyond this threshold.

What to do

Parapholis in its natural coastal habitat requires no intervention and times its lifecycle according to natural conditions each year; it self-seeds and maintains its coastal populations without management. In a specialist coastal garden or naturalistic coastal planting where it is cultivated deliberately, no watering is needed or appropriate; the plant is very well adapted to the coastal environment and human intervention typically does more harm than good.

Annual lifecycle completion and die-back

Parapholis germinates in autumn or early spring, flowers from May to July, and dies after seed set in July to August. The leaves yellow and curl from the plant base upward as it ripens, the pencil-thin spike turns from green to straw-yellow, and the whole plant dries. The dried, straw-coloured, rigid spikes remain standing on sea walls and coastal paths through late summer as a distinctive structural feature of the coastal flora.

What to do

Allow the plants to ripen fully and shed seed; parapholis self-seeds readily in suitable open coastal conditions without any management; the very fine seed falls close to the parent plant and germinates in the same open, saline, thin-soil position in autumn. The dried spikes are structurally distinctive in the coastal flora and do not need removal; they decay naturally over the autumn and winter.

Non-coastal growing conditions

Parapholis is a coastal specialist adapted to the combination of thin, saline or salt-spray-influenced soil, exposure, and the coastal microclimate; when grown in a standard inland garden soil without salt exposure, it performs less vigorously than in its natural habitat. The absence of coastal conditions does not prevent growth but may affect vigour and longevity through the season.

What to do

If growing parapholis in a garden setting, replicate coastal conditions as closely as possible: very thin, gritty, freely draining, open-textured soil or substrate; full sun; no added fertiliser or organic matter; sparse, low-competition surroundings; an exposed, windy position is actually beneficial rather than detrimental for this coastal-adapted species. The plant does not need salt to perform well in a garden context but prefers the lean, thin-soil, open-ground conditions of its natural coastal habitat.

Frequently asked questions

Why are my parapholis leaves curling?

Parapholis leaves curl most commonly because of drought in thin coastal soils (fine shallow annual roots; narrow leaves roll more tightly and tip-brown in hot dry summers; coastal habitat means some innate drought tolerance but extreme heat pushes it beyond this; no intervention needed in natural habitat; no watering appropriate in coastal garden planting), natural annual lifecycle completion (germinates autumn to early spring; flowers May to July; leaves yellow from base upward as plant ripens; pencil-thin spike turns straw-yellow; whole plant dries by July to August; allow full seed shed; self-seeds freely in open saline thin-soil conditions), or non-coastal growing conditions (coastal specialist; performs best with thin, gritty, freely draining, open-textured soil in full sun; no added fertiliser or organic matter; sparse low-competition surroundings; exposed windy position beneficial). Zero-maintenance in the right open, lean, sunny coastal or coastal-replica position.

Where does parapholis strigosa grow in the UK?

Strongly coastal distribution primarily in south and south-east England. Sea walls and coastal embankments: top and face of coastal sea walls, earth embankments, and flood defences in estuaries and coastal grazing marshes; characteristic in south-east England. Upper saltmarsh and saltmarsh margins: drier, most landward parts of saltmarsh in the transition zone. Coastal paths and cliff-tops: thin, sun-baked, slightly saline soil of coastal footpaths and cliff-top grassland. Dune slacks and sandy coastal ground: open, sunny, calcareous dune slacks and exposed dune-system ground. UK distribution: primarily Kent, Essex, Suffolk, Norfolk, Dorset, Hampshire, Isle of Wight, West Sussex, East Sussex, Devon, Cornwall; also Welsh coast and parts of Ireland; rare in northern England and Scotland. P. incurva is more southern and rarer.

How is parapholis related to other UK grass genera?

Placed in tribe Poeae; closest to Lolium (ryegrasses): both share the feature of true spikes with spikelets embedded in the rachis with no pedicels (stalks); Lolium spikelets are edge-on to the rachis, Parapholis spikelets are face-on. Hainardia cylindrica (Mediterranean ryegrass): superficially almost identical pencil-thin spike; distinguished by technical spikelet characters; occasional coastal casual in southern UK. Catapodium marinum (sea fern grass): frequently co-occurs with Parapholis at UK coastal sites but has a branched fern-like panicle rather than a spike. Puccinellia: co-occurs in coastal habitats; perennial; open branching panicle; more tightly associated with wetter, more frequently flooded saltmarsh.

What other annual grasses are found in UK coastal habitats?

Parapholis strigosa (hard grass): pencil-thin cylindrical spike; sea walls, upper saltmarsh, coastal paths; characteristic and easily identified. Parapholis incurva (curved hard grass): more curved spikes; more southern and rarer. Catapodium marinum (sea fern grass): stiff one-sided fern-like branching panicle; coastal paths and sea walls. Hordeum marinum (sea barley): bristly barley-like spike; coastal grassland and sea walls; smaller than wall barley. Puccinellia fasciculata and P. rupestris: annual or biennial saltmarsh grasses of drier upper saltmarsh and coastal turf. Mibora minima (early sand grass): one of UK's smallest native grasses; sandy coastal ground in Wales and south-west England; flowers February to April; rare. Rostraria cristata: Mediterranean casual on coastal sandy ground in southern England.