Plant problems

Why Are My Hordeum Leaves Curling?

Q: How do I identify hordeum murinum in the UK?

Hordeum murinum (wall barley, mouse barley) is one of the most easily identified and commonly encountered annual grasses in the UK urban environment; it is found virtually everywhere from pavement cracks and the base of walls in city centres to roadsides, gravel car parks, railway embankments, and disturbed waste ground throughout lowland England and Wales; it is commoner in the south and east and in urban and suburban areas. Key identification features: Habit: an annual grass growing as a rosette of flat, green leaves overwinter; then rapidly upright to 20 to 60 cm with a distinctive, erect, symmetrical, cigar-shaped to narrowly cylindrical ear (spike) at the top of each stem. Leaves: flat, mid-green, 3 to 7 mm wide, hairy on both surfaces; the leaf sheaths are slightly inflated and the leaf bases have small, pointed ear-like projections (auricles) clasping the stem, similar to wheat and barley. Spike: the most distinctive feature; a dense, symmetrical, barley-like spike with three spikelets at each node of the rachis (stem axis); the central spikelet is fertile and produces a grain; the two lateral spikelets are sterile and awn-like; all three spikelets bear long, spreading, stiff awns (3 to 4 cm long) that give the whole spike a very bristly, prickly, bottle-brush appearance; the awns spread outward to give a distinctly star-burst cross-section when the spike is viewed from above. Flowering and ripening time: April to July; the plant is at its most conspicuous when the erect, bristly spikes emerge from the leaf sheaths in April to May and ripen straw-yellow in June to July. Confusion species: Hordeum distichon and H. vulgare (cultivated barley) are much larger; Hordeum secalinum (meadow barley) has a narrower, more nodding ear and grows in old meadows rather than disturbed urban ground; Hordeum marinum (sea barley) is similar but found only in coastal habitats.

Q: Is hordeum jubatum an ornamental grass for UK gardens?

Hordeum jubatum (foxtail barley, squirreltail barley, squirreltail grass) is a short-lived perennial (often grown as an annual) ornamental grass native to temperate North America and north-east Asia, popular as an ornamental annual grass in UK gardens and cutting gardens for its distinctive, fluffy, pendant, fox-tail like flower spikes; it is one of the most ornamentally attractive grasses in the barley genus and is grown specifically for the extraordinary visual effect of its ripe flower heads. The flower heads of Hordeum jubatum are very long-awned (awns 5 to 9 cm), silky, and soft to the touch; when they first emerge they are bright green with pinkish, purplish, or silvery tips; as they ripen they turn to a luminous, pale buff-straw colour; the awns spread at a wide angle, giving the head a very open, feathery, fox-tail-like appearance that trembles and shimmers in the breeze in a very attractive way; the heads are produced from June to August. Growing Hordeum jubatum in the UK: grow as a half-hardy annual; sow seed in modules or cells under glass in February to March at 15 to 20°C; plant out after last frost risk in late May; alternatively, direct sow outside in April to May; a well-drained, moderately fertile soil in full sun is ideal; it is more tolerant of poor, dry, light soils than most ornamental grasses. Harvest for drying: harvest the flower heads for use as cut or dried flowers when they are at the soft, silky, fully open green to pale buff stage; once fully ripe, the spikelets shatter and the awns fall off, greatly reducing the ornamental value of the harvested heads; harvest early, before the heads shatter. Caution: the sharp, barbed awns and florets of H. jubatum can cause mechanical injury and can work into the fur of pets, embedding in skin; handle with care and keep away from cats and dogs.

Q: What UK grasses grow in pavement cracks and walls?

A distinctive community of annual and perennial grasses and grass-like plants specialises in the harsh, dry, nutrient-poor, compacted, free-draining conditions of pavement cracks, the base of walls, and urban hard surfaces in the UK. These plants are adapted to survive drought, compaction, mechanical damage from foot traffic, and the extreme temperature fluctuations of heat-absorbing hard surfaces: Hordeum murinum (wall barley): the most characteristic UK urban pavement grass; common annual; bristly, barley-like spikes; germinates in autumn; ripens May to July; very common in southern UK urban areas. Poa annua (annual meadow grass): the most ubiquitous UK grass overall; also a dominant pavement crack colonist; tiny, neat, tufted annual or short-lived perennial; small, open, triangular panicle; flowers almost year round in mild UK winters; extremely drought-tolerant once established. Poa trivialis (rough meadow grass): also in paving cracks in damper, shadier positions; perennial. Eragrostis spp. (love grasses): casual introductions from warmer climates, increasingly recorded in urban south-east UK on warm, sunny, south-facing pavements and walls; Eragrostis minor (small love grass) and E. cilianensis (stink grass, feather love grass) are occasional warm-summer pavement crack colonists. Setaria spp. (bristle grasses): occasional pavement crack and disturbed ground colonists in south-east UK from bird seed or impure grass seed imports; Setaria viridis and S. pumila are the most frequent species encountered. Sporobolus indicus (rat-tail grass): an increasing casual in UK urban areas; more common in the south. Annual mercury (Mercurialis annua), shepherd's purse (Capsella bursa-pastoris), and wall-rocket (Diplotaxis muralis) commonly accompany the grass community in pavement cracks.

Hordeum murinum (wall barley, mouse barley) is a very common UK native annual grass of pavement cracks, roadsides, walls, and urban disturbed ground. Hordeum secalinum (meadow barley) is a perennial of old hay meadows; Hordeum jubatum (foxtail barley) is an ornamental annual prized for its silky, feathery, fox-tail flower heads. Leaves curl and yellow from drought in thin soils, competition in dense stands, or the natural summer ripening and senescence of the annual lifecycle.

Drought and dry thin soil

Wall barley germinates in autumn and overwinters as a small rosette before growing rapidly in spring; in prolonged dry spells in late spring or early summer, the flat leaves roll inward from the margins and the leaf tips yellow and brown from drought stress. The plant grows in thin, free-draining urban soils and is reasonably drought-tolerant, but extended drought causes visible leaf curl; drought stress is usually temporary and the plant recovers after rain or proceeds to ripen.

What to do

As a weed of urban and garden settings, drought-stressed wall barley plants are in a weakened state and should be removed by hand or hoe before they recover and set seed; in dry, crumbly soil, the shallow roots pull out very easily. In a garden where hordeum jubatum is grown as an ornamental, water in prolonged dry periods in late spring to maintain the fresh, upright, healthy growth needed for the best ornamental display; the plant produces its best flower heads in a warm, sunny, dry position but requires occasional deep watering to prevent drought curl of the leaves.

Competition and shading

Wall barley is a plant of open, bare, disturbed ground with very low competition; in a position where it is shaded or crowded by surrounding taller vegetation, the plant becomes etiolated and the leaves are softer, broader, and more prone to curling and rolling. The characteristic stiff, symmetrical, upright spikes of wall barley in open conditions are replaced by weaker, floppy, pale growth that is more easily missed and more likely to set seed without detection in a mixed border.

What to do

Check along the base of walls, fences, and hedges, and in the gaps between border plants, where wall barley can establish in low-competition micro-habitats that are partially shaded and easy to overlook; remove promptly before the spikes emerge and set seed. For ornamental hordeum jubatum, thin sown plants to 20 to 30 cm spacing; overcrowding reduces the size and quality of the individual flower heads and causes etiolation and leaf curl in crowded plants.

Summer ripening and senescence

Hordeum murinum is an annual that dies after setting seed from May to July; the entire above-ground growth yellows, curls, and dries into the characteristic straw-coloured, prickly, bristly mass of dried spikelets that remain on disturbed ground through summer. This seasonal die-back is entirely normal for an annual grass. The dried, straw-coloured spikes are characteristic of urban roadsides and pavements from June onwards and the stiff, barbed awns can embed in the fur of cats and dogs.

What to do

Remove dried wall barley plants before the ripe spikes shatter to prevent seed dispersal and soil seedbank accumulation; grasp the stem below the ear, pull the whole plant, and dispose of in garden waste rather than composting. The barbed, stiff awns of H. murinum can cause mechanical injury to pets: check pets for embedded awns after they have been in areas where wall barley grows, particularly around the feet, face, and ears; the awns can work progressively deeper into the skin or even into the ear canal with time if not removed promptly.

Frequently asked questions

Why are my hordeum leaves curling?

Hordeum leaves curl most commonly because of drought in thin or dry soil (wall barley is an autumn-germinating annual; flat leaves roll inward in drought stress; leaf tips yellow; most visible in late spring on dry, thin urban soils; remove drought-stressed weeds while roots are shallow and easy to pull; water ornamental H. jubatum in prolonged dry spells), competition and shading (open, bare-ground plant; etiolated, pale, curling leaves in crowded or shaded positions; check base of walls and gaps between border plants; thin ornamental plantings to 20 to 30 cm), or summer ripening and senescence (normal annual lifecycle; entire plant yellows and dies after seed set in May to July; remove before spikes shatter; dispose of in garden waste not compost; check pets for embedded awns). The weed management priority is always: prevent seed set.

How do I identify hordeum murinum in the UK?

Very common UK urban annual grass. Habit: rosette of flat green hairy leaves in winter; rapidly upright to 20 to 60 cm with a dense, symmetrical, cigar-shaped spike in April to July. Leaves: flat, mid-green, 3 to 7 mm wide, hairy; small pointed auricles (ear-like projections) at the leaf base clasping the stem. Spike: most distinctive feature; three spikelets at each node; central fertile, two lateral sterile and awn-like; all bear long, stiff, spreading awns (3 to 4 cm) giving a very bristly, bottlebrush appearance; awns spread outward giving a star-burst cross-section from above. Flowering May to July; straw-yellow when ripe. Found in pavement cracks, wall bases, roadsides, rubble, disturbed urban ground throughout lowland UK; much commoner in the south and east.

Is hordeum jubatum an ornamental grass for UK gardens?

Yes; one of the most ornamentally attractive annual grasses in the barley genus. Short-lived perennial grown as a half-hardy annual. Distinctive, fluffy, pendant, fox-tail-like flower spikes with very long awns (5 to 9 cm) that are silky, soft to touch, and luminously pale buff-straw when ripe; produced June to August. Grow from seed under glass February to March at 15 to 20°C; plant out after last frost in late May; or direct sow outside April to May. Well-drained, moderately fertile soil in full sun. Harvest for drying at the green-to-pale-buff stage before spikelets shatter. Caution: sharp, barbed awns can cause mechanical injury and embed in pets' fur; keep away from cats and dogs; handle with care.

What UK grasses grow in pavement cracks and walls?

Hordeum murinum (wall barley): most characteristic UK urban pavement grass; bristly barley-like spikes; very common in southern UK. Poa annua (annual meadow grass): most ubiquitous UK grass overall; dominant pavement crack colonist; tiny tufted annual or short-lived perennial; flowers almost year round. Eragrostis spp. (love grasses): increasing casuals in warm, sunny south-east UK pavements; E. minor and E. cilianensis are the most frequent. Setaria spp. (bristle grasses): occasional colonists from bird seed imports; S. viridis most frequent. Sporobolus indicus (rat-tail grass): increasing casual in UK urban areas. Poa trivialis: in damper, shadier paving cracks. Non-grass companions: annual mercury, shepherd's purse, wall-rocket.