Plant problems

Why Are My Bromus Leaves Curling?

Q: How do I identify the common UK bromus species?

The three most commonly encountered Bromus species in the UK differ in habitat, growth form, annual or perennial lifecycle, and the character of their flower panicle and spikelets: Bromus sterilis (barren brome, poverty brome): a tall annual or biennial (to 100 cm) of disturbed ground, roadsides, hedgerow bases, arable field margins, and gardens; the most common UK brome; distinctive, very large, drooping panicle of large, flat, long-awned spikelets that hang downward at long, thin, drooping stalks (pedicels); the whole panicle has a graceful, pendant, one-sided, nodding appearance; the spikelets are very large (25 to 40 mm long including awn) and the awns are long (15 to 20 mm), straight, and spreading; leaves are flat, softly hairy, mid-green. Bromus hordeaceus (soft brome, lop grass, common soft brome): a smaller annual (to 80 cm) of meadows, grassland, arable field margins, and roadsides; more compact and upright than B. sterilis; the panicle is more erect and the spikelets are smaller and more tightly packed; the whole plant is softly hairy, giving it a distinctive soft, velvety feel; the spikelets are oval to oblong (10 to 20 mm); very common throughout the UK. Bromus erectus (upright brome, tor grass, chalk false-brome): a perennial (to 100 cm) of chalk and limestone grassland, dry banks, road cuttings on chalk, and calcareous scrub margins; the only UK brome that is a typical perennial of semi-natural calcareous grassland rather than a weed; forms dense, tussocky stands; upright, narrow, stiff panicle; smaller spikelets than B. sterilis; a conservation-important species, dominant in much traditional chalk downland but can become over-dominant and suppress biodiversity when grazing is removed.

Q: Can bromus be grown ornamentally in a UK garden?

Several Bromus species are grown as ornamental annual grasses in UK gardens and cutting gardens, valued for their distinctive, large, drooping, nodding, pendant panicles with long awns that provide a graceful, airy, informal texture in a mixed border or cottage garden: Bromus sterilis (barren brome): although primarily known as a UK arable weed, the very large, gracefully drooping panicles of B. sterilis are genuinely ornamental; the pendant, long-awned spikelets hang elegantly from thin pedicels and the whole panicle has an airy, open, graceful character that is very effective in a naturalistic or wildflower border; it is very easy to grow (it grows itself as a weed in many UK gardens) and the panicles are attractive as cut or dried flowers. Bromus briziformis (brizoid brome, rattlesnake brome): the most deliberately cultivated ornamental brome in UK gardens; has very large, inflated, oval, quaking-grass-like spikelets that resemble a much larger version of Briza media; the drooping panicle of large, boat-shaped, pale green to straw-gold spikelets is one of the most distinctive and ornamental of any grass available to UK gardeners; grow from seed sown in spring in a well-drained, moderately fertile, sunny border; excellent for cut flowers and drying. Bromus macrostachys and Bromus lanceolatus: other Mediterranean annual brome species occasionally grown for their ornamental panicles in UK gardens and cutting gardens; all require well-drained, sunny positions and are grown from spring-sown seed. For a UK garden, Bromus briziformis is the most ornamentally distinct and worth seeking out specifically; Bromus sterilis can be admitted as a naturalised ornamental plant in a naturalistic or wildlife garden but must be managed to prevent excessive seeding.

Q: Is bromus erectus good for chalk grassland conservation in the UK?

Bromus erectus (upright brome, tor grass) is the dominant grass of much traditional chalk and limestone downland in southern England; it is a native UK perennial grass of conservation importance as a characteristic component of the CG2 (Festuca ovina-Avenula pratensis) and CG3 (Bromus erectus) NVC chalk grassland communities; it supports a range of specialist invertebrates including the brown argus butterfly (Aricia agestis), various chalk-specialist grasshoppers and bush-crickets, and numerous chalk downland moths, beetles, and flies. However, Bromus erectus is simultaneously one of the main threats to chalk grassland biodiversity in the UK when traditional management is removed: without grazing or regular cutting, Bromus erectus rapidly becomes dominant in a chalk grassland sward, suppressing the diverse community of fine-leaved chalk grassland grasses (festuca, avenula, helictochloa, briza, carex) and specialist chalk wildflowers (Thymus, Astragalus, Polygala, Hippocrepis, Cirsium acaule, Scabiosa, and many others) that characterise high-quality UK chalk downland; a coarse, rank Bromus erectus monoculture is one of the characteristic signs of under-managed or ungrazed chalk grassland. Management recommendations for chalk grassland: maintain regular livestock grazing (sheep, cattle, or ponies) from late summer through winter; or mow once or twice per year (late summer or autumn cut with the cuttings removed); grazing and cutting prevent Bromus erectus becoming rank and dominant and allow the diverse chalk grassland flora to persist; the traditional management of UK chalk downland by rabbit grazing (before the myxomatosis epidemic of the 1950s), sheep grazing, and cutting created and maintained the exceptionally species-rich grassland communities that are now among the most biodiverse habitats in the UK.

The UK brome grasses include Bromus sterilis (barren brome), Bromus hordeaceus (soft brome), and Bromus erectus (upright brome, tor grass). The annual species are common weeds of disturbed ground and arable field margins; Bromus erectus is a native perennial of chalk and limestone grassland and a conservation-important species. Leaves curl from drought on thin soils, competition and shading in dense swards, or the natural ripening and die-back of annual species in summer.

Drought and dry soil

Annual brome species germinate in autumn and overwinter as rosettes; their shallow root systems cause the soft, hairy leaves to roll inward and the leaf tips to yellow in prolonged dry conditions in late spring and early summer on thin, sandy, chalk-based, or compacted soils. Annual species typically ripen and die in June to July regardless of moisture, so drought stress in late spring is usually temporary. Bromus erectus is a perennial with a deeper root system and can better access subsoil moisture on thin chalk soils in summer.

What to do

In a garden context, drought-stressed annual brome plants are in a weakened state ideal for hand removal or hoeing; remove before the panicle opens and seed is shed, especially Bromus sterilis (barren brome) which is a persistent arable weed with a large soil seedbank. For ornamental brome species (particularly Bromus briziformis grown as an annual in a cutting garden), water in dry spells in May and June to maintain the full, lush growth needed for the best-formed, most attractive panicles.

Competition and shading

Brome grasses in dense swards or shaded by surrounding perennial border plants show leaf curl, etiolation, and yellowing in the lower, more shaded leaves. Bromus sterilis in a dense sward produces noticeably weaker, more lax growth than the same species in an open, disturbed position; it is a plant of open, disturbed ground with low competition and performs best in these conditions. In a conservation chalk grassland context, dense competition from Bromus erectus itself can suppress the diverse chalk flora when grazing is removed.

What to do

Remove annual brome weeds before they become shaded and less visible in a dense border or sward; plants that are shaded or crowded are harder to spot and more likely to set seed without detection. In a chalk grassland, maintain regular grazing or cutting to prevent Bromus erectus becoming dominant and suppressing the diverse chalk flora it otherwise coexists with under traditional management.

Annual ripening and die-back

Annual and biennial brome species complete their lifecycle from autumn germination to summer seed ripening in one to two growing seasons. As they ripen from June to July, the lower leaves yellow, curl, and die back; the characteristic drooping or nodding panicle turns from green to pale straw-gold. This is entirely normal and is the natural completion of the annual lifecycle, not a disease or cultural problem.

What to do

Remove annual brome weed plants before the panicle ripens fully and seed is shed; once the long-awned spikelets begin to shatter, that year's contribution to the soil seedbank cannot be prevented. For ornamental annual bromus, harvest the panicles at the fresh, green-ripe stage for the best cut and dried flower quality; fully ripened, shattered spikelets are much less attractive as dried material.

Frequently asked questions

Why are my bromus leaves curling?

Bromus leaves curl most commonly because of drought and dry soil (annual species have shallow roots; soft hairy leaves roll in dry conditions in late spring on thin, sandy, or chalk soils; remove drought-stressed weed plants before seed shed; water ornamental brome in May to June for best panicle quality), competition and shading (annual brome in dense swards becomes etiolated and weak with curling lower leaves; remove weed plants early before they are hidden by surrounding growth; maintain grazing or cutting to prevent B. erectus becoming dominant in chalk grassland), or annual ripening and natural die-back (lower leaves yellow and curl as the annual ripens June to July; normal lifecycle completion; remove weed plants before seed shed; harvest ornamental panicles at the fresh green-ripe stage for best dried flower quality). Prevent seed set at every opportunity.

How do I identify the common UK bromus species?

Bromus sterilis (barren brome): tall annual to 100 cm; most common UK brome; very large, gracefully drooping panicle with long-pedicelled pendant spikelets (25 to 40 mm including awn); awns long (15 to 20 mm), straight, spreading; disturbed ground, roadsides, hedgerow bases, arable field margins. Bromus hordeaceus (soft brome): smaller annual to 80 cm; more compact and upright than B. sterilis; softly hairy throughout (distinctively velvety feel); smaller spikelets (10 to 20 mm); common in meadows, grassland, and arable margins throughout UK. Bromus erectus (upright brome, tor grass): perennial to 100 cm; chalk and limestone grassland only; upright, narrow, stiff panicle; smaller spikelets; forms dense tussocky stands; conservation-important native of calcareous grassland.

Can bromus be grown ornamentally in a UK garden?

Yes. Bromus briziformis (brizoid brome): the most ornamentally distinct; very large, inflated, oval, quaking-grass-like spikelets; drooping panicle of large boat-shaped pale green to straw-gold spikelets; unlike anything else available; grow from spring-sown seed in well-drained, sunny border; excellent for cut and dried flowers. Bromus sterilis (barren brome): ornamental pendant panicles in a naturalistic or wildflower border; very easy to grow; must be managed to prevent excessive seeding. Bromus macrostachys, B. lanceolatus: other Mediterranean annual brome species with ornamental panicles; grown from spring-sown seed in well-drained, sunny positions.

Is bromus erectus good for chalk grassland conservation in the UK?

Bromus erectus is both a conservation-important native species and a management challenge. It is dominant in CG2 and CG3 NVC chalk grassland communities; supports specialist invertebrates including the brown argus butterfly, chalk grasshoppers, and chalk downland moths and beetles. Without grazing or cutting, it becomes dominant and suppresses the diverse chalk flora (Thymus, Astragalus, Polygala, Hippocrepis, Cirsium acaule, and many others) that characterises high-quality UK chalk downland. Management: maintain regular sheep, cattle, or pony grazing from late summer through winter; or mow once to twice per year in late summer with cuttings removed; this prevents rank, dominant B. erectus and allows the diverse chalk flora to persist.