Plant problems

Why Are My Aira Leaves Curling?

Q: How do I grow aira elegantissima in a UK garden?

Aira elegantissima (hair grass, elegant hair grass) is best grown in a UK garden from seed sown directly in the position where it is to grow, in autumn (September to October) or in very early spring (February to March) in a sunny, very freely draining position in light, sandy, low-fertility, neutral to slightly acid soil. It performs exceptionally well in containers filled with a very free-draining, gritty compost (equal parts good quality potting compost and fine horticultural grit or coarse sand), where its delicate, cloud-like flower display can be seen at close range and the drainage conditions can be precisely controlled. It is less successful in a heavy, clay, moisture-retentive garden soil, which should be lightened significantly with coarse grit or sharp sand before sowing. Sow on the surface or barely cover the fine seed; aira seed is tiny and requires good light contact with the soil to germinate reliably. Thin seedlings to 10 to 15 cm apart to allow each plant space to develop the full, rounded, airy flower cloud that is its most ornamental feature. Do not feed; aira thrives in low-fertility conditions and excessive feeding promotes soft, coarse foliage at the expense of the delicate flower cloud. Do not overwater; keep the growing medium just moist, not wet. The finest display — a trembling, silver-white cloud of hair-fine flower stems and tiny spikelets — develops from late April to June in a sunny, freely draining position; the flowers are at their most beautiful when the morning or evening sun is low and lights the silver spikelets from behind. After flowering and seeding in July to August, the plants die (being annual or biennial); collect seed for resowing the following autumn, or allow self-seeding into the surrounding open soil in suitable conditions.

Q: Is aira elegantissima good for cutting and drying?

Yes, Aira elegantissima (hair grass) is one of the most delicate and beautiful annual grasses for cutting and drying, and the dried flower and seed heads are an exceptionally fine and delicate addition to dried flower arrangements, pressed flower work, and botanical crafts. The tiny, silver-white, hair-fine spikelets and their trembling, branched stems maintain their delicate, airy structure remarkably well when cut and dried, retaining the cloud-like, floating quality that makes the fresh plant so distinctive. For the best results in cutting and drying, cut the stems when the flower heads are fully developed but the seed is not yet mature — typically in late May to early June in a UK garden — when the spikelets are at their most silver and pristine; if cut too early the spikelets are not fully developed, and if cut after the seed has matured and begun to shatter, the seed heads lose their pristine appearance. Hang the cut stems in small, loose bunches in a warm, dry, airy position in the shade for two to three weeks; aira dries quickly because of the fine, hair-like stem structure. Dried aira stems are extremely fragile and should be handled gently; the charm of the dried material is in the delicacy and fragility of the individual spikelets rather than in bold colour or robust texture. Fresh cut stems of aira in the short-lived cutting garden phase (May to June) can also be used in fresh flower arrangements, where they add a fine, misty, silver haze that is difficult to replicate with any other plant material in the UK spring and early summer garden.

Q: Is aira native to the UK?

Yes, both Aira caryophyllea (silver hair grass) and Aira praecox (early hair grass) are native UK grasses of dry, sandy, acid, impoverished habitats including heathland, sandy grassland, open sandy roadsides, wall tops, and sandy or gravelly ground across England, Wales, Scotland, and Ireland; they are characteristic species of the driest, most nutrient-poor, freely draining, acid sandy habitats in the UK, and their presence in a heathland or sandy grassland is typically an indicator of long-established, unimproved, low-fertility conditions. Aira praecox (early hair grass) flowers earlier (March to May) than A. caryophyllea (April to June) and is generally a slightly smaller, more compact plant. In the UK context, both species are relatively common in their preferred dry, sandy habitats in the south and east of England, particularly on heathland, acidic sandy commons, old sand pits, and sandy road verges; they are less common in the moister, more calcareous conditions of much of central, northern, and western Britain. The ornamental selection Aira elegantissima, widely sold as a garden annual, is a form selected for particularly fine, delicate flower heads and is regarded either as a cultivar of A. caryophyllea or as a separate species (there is some taxonomic disagreement); it is not a UK native in the strict sense but is derived from species that are close relatives of the UK native aira species. The UK native aira species are part of the characteristic flora of UK heathland, a listed UK Biodiversity Action Plan priority habitat that has declined dramatically in the twentieth century; aira plays a characteristic role in the early-succession, open, bare, sandy phases of heathland habitat.

Aira elegantissima (hair grass) is a delicate annual or biennial grass producing spectacular clouds of tiny, silver-white, trembling flower spikelets from May to July; outstanding in containers, a border front, or a cutting garden. An annual of dry, sandy, acid, impoverished ground. Overwatering and too-fertile or heavy soil are the most common problems; summer die-back after seeding is normal annual lifecycle behaviour.

Overwatering and wet, heavy soil

Aira thrives in the freely draining, light, sandy, dry conditions that most garden plants find inhospitable; in heavy, moist, clay-rich soil, the very fine leaves collapse, yellow, and rot at the base. Overwatering in a container is the most common cause of failure: the fine, annual root system is quickly damaged by persistently waterlogged compost. The flower cloud that is the plant's main appeal only develops properly in dry, freely draining, warm conditions.

What to do

Grow in very freely draining, light, sandy, or gritty soil; lighten a heavy garden soil significantly with coarse grit or sharp sand before sowing. In containers, use equal parts good potting compost and fine horticultural grit; ensure drainage holes are fully open. Water sparingly; keep the growing medium just barely moist, not wet. In the right dry, gritty conditions, aira virtually looks after itself from late spring to summer without supplementary watering in a typical UK garden.

Too much fertility

Aira is a grass of acid, impoverished, low-fertility sandy ground; in rich, fertile garden soil it produces excessive coarse foliage and fewer of the delicate hair-fine flower heads. Soft, coarse growth in fertile conditions is also more susceptible to fungal damping off and root rot. Do not feed aira in a typical garden soil; it performs best in conditions most other plants find too poor to thrive.

What to do

Do not add fertiliser or enriched compost. In a container, use a free-draining, low-nutrient mix rather than a standard peat-based or coir-based potting compost. If a border soil is naturally fertile, aira is not the right plant; it is better suited to a gravel garden, a raised bed of gritty substrate, or a container with a purpose-prepared low-fertility, very free-draining mix. In the right conditions the flower cloud is spectacular; in the wrong conditions it refuses to develop properly.

Normal summer die-back

Aira elegantissima and A. caryophyllea are annual or biennial grasses; they germinate in autumn or early spring, produce their finest foliage and the spectacular cloud of silver flowers from May to June, then set seed and die as summer heat arrives. What appears to be 'curling and dying' in June to July is often simply the plant completing its annual lifecycle; this is entirely normal and not a cultural failure. Collect seed for resowing the following autumn, or allow self-seeding in suitable open, gritty conditions.

What to do

Accept the annual lifecycle; plan the planting to accommodate the gap left when aira dies back in July. Collect ripe seed in June to July and resow in autumn (September to October) or early spring (February to March) for the following season's display. In a gravel garden or open, gritty condition, aira often self-seeds reliably without intervention; the tiny seeds germinate readily in the fine, open, well-drained conditions of a gravel surface.

Frequently asked questions

Why are my aira leaves curling?

Aira leaves curl and die back most commonly because of overwatering or wet, heavy soil (annual grass of dry, sandy, impoverished ground; very free-draining, light, gritty soil; water sparingly; equal parts compost and grit in containers), too much fertility (do not feed; in rich soil produces coarse foliage and few flower heads; gravel garden or low-fertility raised bed), or normal summer die-back after seeding (annual lifecycle; flowers May to June; seeds and dies July to August; collect seed for resowing; allow self-seeding in open gritty conditions). Dry, gritty, low-fertility conditions are the key.

How do I grow aira elegantissima in a UK garden?

Sow seed directly in autumn (September to October) or early spring (February to March) in a sunny, very freely draining, light, sandy, low-fertility, neutral to slightly acid position. Alternatively, sow in containers of equal parts potting compost and fine horticultural grit. Barely cover the tiny seed; it needs light contact with the soil to germinate. Thin to 10 to 15 cm apart. Do not feed. Water sparingly. The finest cloud-like silver flower display develops from late April to June; most beautiful backlit by low morning or evening sun. After seeding in July to August, collect seed for resowing or allow self-seeding in open, gritty conditions.

Is aira elegantissima good for cutting and drying?

Yes; one of the most delicate and beautiful annual grasses for cutting and drying. The tiny, silver-white, hair-fine spikelets maintain their cloud-like, floating structure very well when cut and dried. Cut when flower heads are fully developed but before seed shatters (late May to early June). Hang in small, loose bunches in a warm, dry, airy, shaded position for two to three weeks. Handle dried material gently as it is extremely fragile. Fresh-cut stems add a fine, misty, silver haze to spring and early summer flower arrangements that is difficult to replicate with any other plant material.

Is aira native to the UK?

Yes; A. caryophyllea (silver hair grass) and A. praecox (early hair grass) are native UK grasses of dry, sandy, acid, impoverished heathland, sandy grassland, wall tops, and open sandy ground. A. praecox flowers earlier (March to May) and is slightly smaller. Both characteristic of the driest, most impoverished, freely draining acid sandy habitats in southern and eastern England. Component of UK heathland habitat (a UK Biodiversity Action Plan priority habitat) in the early-succession, open, bare, sandy phase. The ornamental A. elegantissima is a selected form from the same genus, not a strict UK native.