Plant problems

Why Are My Hainardia Leaves Curling?

Q: What other Mediterranean annual grasses occur as casuals in the UK?

The UK coastal and southern England casual grass flora includes a fascinating range of Mediterranean and southern European annual grasses that arrive as introductions via sea trade, ballast, imported sand, seed contamination, and human movement; most are very rare casuals that do not persist long at any one UK site but recur at new sites as new introductions continue. The main Mediterranean annual grass casuals recorded in the UK include: Hainardia cylindrica (Mediterranean ryegrass): pencil-thin cylindrical spike; very rare coastal casual in southern England; superficially similar to Parapholis. Aegilops species (goat grasses): several Aegilops species (particularly Aegilops triuncialis, A. geniculata, A. neglecta) are recorded as rare casuals in the UK, primarily in coastal and disturbed ground in southern England; they have distinctive, somewhat bristly, ovoid to cylindrical spikes that are quite different from any native UK grass. Catapodium marinum (sea fern grass): a possibly native coastal species with a stiff, fern-like, one-sided panicle; more common than Hainardia at UK coastal sites but still primarily southern. Gastridium ventricosum (nit grass): nationally scarce but established (perhaps native) on chalk grassland in southern England; glistening, nit-like swollen glume bases. Rostraria cristata (Mediterranean hair grass): occasional casual on coastal sandy ground in southern England; compact cylindrical flower spike; also cultivated as an ornamental annual. Phalaris paradoxa (awned canary grass): an occasional casual of disturbed ground, ports, and imported-seed spillage. Lolium temulentum (darnel): now largely extinct as a UK weed of cereal crops but historically associated with cereal fields and recorded as a rare casual. Polypogon monspeliensis (annual beard grass): established naturalised species in coastal and wet disturbed ground.

Hainardia cylindrica (Mediterranean ryegrass, one-glumed ryegrass) is a very rare annual grass casual of southern England coastal and disturbed ground, distinguished from the similar Parapholis (hard grass) by having only one visible glume per spikelet. A Mediterranean species occasionally cultivated by grass enthusiasts. Leaves curl and die back from drought in thin substrates, rapid summer ripening of the annual lifecycle, or cold and wet stress in cooler UK summers unlike its native climate.

Drought in thin, open substrate

A Mediterranean annual more drought-tolerant than many northern European grasses, hainardia still shows visible leaf stress in prolonged dry spells in UK conditions; the narrow leaves roll inward and the leaf tips brown as moisture in the thin, freely draining substrate is depleted. Most vulnerable in the driest UK summers on very thin coastal sandy or gravelly ground without the regular wetting of a tidal saltmarsh.

What to do

If growing deliberately in a warm, sunny border position: water lightly in very dry spells in May and June before the spike is fully developed; allow the substrate to dry between waterings; the plant is adapted to warm, dry, open conditions and does not need or benefit from persistent irrigation. The warmest, most sheltered, south-facing position with freely draining, lean soil gives the best results in UK conditions.

Summer ripening and die-back

Hainardia flowers from May to July in the UK; the pencil-thin, stiff cylindrical spike ripens rapidly from green to straw-coloured in warm conditions; as the plant ripens, the narrow leaves yellow and curl and the whole plant desiccates and dies after seed set. In good UK conditions the annual lifecycle from germination to seed set can be completed in two to three months.

What to do

For botanical or ornamental interest, observe the spike at the fresh-green, fully developed stage when its pencil-thin, cylindrical character is most clear and can be compared with the very similar Parapholis; this is the optimal time for identification photography and close examination with a hand lens. The plant requires no management action at ripening; allow it to set seed in open sandy or gravelly ground for natural regeneration the following year if the site conditions are appropriate.

Cold and wet stress

Hainardia is adapted to warm, sunny, dry Mediterranean growing conditions; in a cool, wet, dull UK spring or summer it grows slowly and may not complete its lifecycle successfully; the leaves yellow and curl from cold and wet stress in conditions that are the opposite of its natural climate. This is the most common reason for poor performance of this species in UK cultivation.

What to do

Choose the absolute warmest, sunniest, most sheltered position available; a south-facing wall base, a gravel bed against a heat-retaining stone or brick wall, or a sunny south-facing raised trough in freely draining, lean, gritty compost are the best UK options; in a cool, wet UK summer hainardia may simply fail to thrive and Parapholis strigosa or Catapodium rigidum from similar pencil-spike ecological niches are more reliable UK alternatives.

Frequently asked questions

Why are my hainardia leaves curling?

Hainardia leaves curl most commonly because of drought in thin open substrate (Mediterranean annual; more drought-tolerant than northern European grasses but still leaf-rolls and tip-browns in prolonged dry UK spells; water lightly in May to June; south-facing freely draining lean soil in the warmest sheltered position; no persistent irrigation), summer ripening and die-back (annual; flowers May to July; spike ripens rapidly from green to straw-coloured; leaves yellow and curl; observe spike at fresh-green fully developed stage; allow seed set for natural regeneration), or cold and wet stress (Mediterranean species; grows slowly in cool wet dull UK summers; may fail to complete lifecycle; choose absolute warmest sunniest most sheltered position; south-facing wall base or gravel bed against heat-retaining wall; Parapholis and Catapodium are more reliable UK alternatives). Warmth and full sun are the key requirements in the UK.

How is hainardia distinguished from parapholis?

Both produce a pencil-thin, stiff, rigid, cylindrical spike with spikelets embedded in the rachis without pedicels (stalks). Key distinction: number of glumes. Hainardia: only ONE visible glume per spikelet (the outer glume is reduced or absent; the common name 'one-glumed ryegrass' refers to this character); examine with a hand lens. Parapholis: TWO glumes visible per spikelet. Habitat distinction in the UK: Parapholis strigosa is a common native species of coastal saltmarsh, sea walls, and coastal paths throughout southern and west-coast UK; encountering a pencil-thin cylindrical spike grass in typical coastal saltmarsh or sea-wall habitat almost certainly means Parapholis, not Hainardia. Hainardia is a very rare casual; unlikely to be encountered outside specialist botanical surveys.

What other Mediterranean annual grasses occur as casuals in the UK?

Hainardia cylindrica (Mediterranean ryegrass): pencil-thin cylindrical spike; very rare coastal casual in southern England. Aegilops species (goat grasses): Ae. triuncialis, Ae. geniculata, Ae. neglecta; rare coastal and disturbed ground casuals; distinctive bristly ovoid to cylindrical spikes. Gastridium ventricosum (nit grass): nationally scarce but established on chalk grassland in southern England; glistening swollen glume bases. Rostraria cristata (Mediterranean hair grass): occasional coastal sandy ground casual; also cultivated ornamentally. Polypogon monspeliensis (annual beard grass): established naturalised species in coastal and wet disturbed ground; very soft silky beard-like panicle. Catapodium marinum (sea fern grass): possibly native coastal species; stiff fern-like panicle. Phalaris paradoxa (awned canary grass): occasional casual of disturbed ground and ports. Most are very rare and recur as new introductions continue rather than establishing persistent self-sustaining populations.

Is hainardia cylindrica related to lolium?

Placed in tribe Poeae (Poaceae), sometimes grouped in or near subtribe Loliinae which also contains Lolium (ryegrasses), Festuca, and Parapholis. Formerly treated as Monerma cylindrica (still listed under this name in some older references). Shares with Lolium the character of spikelets arranged with their flat face presented to the rachis (not their narrow edge as in Hordeum). The single visible glume of Hainardia faces outward in the same orientation as the two glumes of Lolium. The Mediterranean spike-grasses (Hainardia, Parapholis, Pholiurus) form a complex of small annual Mediterranean genera with similar cylindrical-spike morphology; the embedded-spikelet cylindrical-spike form has evolved in Mediterranean annuals as an adaptation to hard, dry, sun-baked, open-ground Mediterranean habitats.