Plant problems

Why Are My Spartina Leaves Curling?

Q: Is spartina pectinata invasive in the UK?

Spartina pectinata (prairie cord grass) and its ornamental cultivar 'Aureomarginata' spread vigorously by underground rhizomes and can colonise a large area of moist garden soil over several years; the rhizomatous spread is the most significant management consideration when siting spartina in a UK garden, as the plant is very difficult to eradicate once established in moist soil where it has spread widely. In a large, informal garden with ample space where it can spread without restriction, spartina pectinata 'Aureomarginata' is a magnificent, structural ornamental grass; in a small or formally managed garden where its spread needs to be controlled, it requires careful management — either growing in a very large container (which requires very frequent watering) or installing a root barrier at least 50 to 60 cm deep around the planting area. It is not classified as invasive or controlled in the UK in the way that some other rhizomatous grasses (such as Fallopia japonica) are, but the vigorous spread of the common North American species Spartina alterniflora has caused significant ecological disruption in UK saltmarsh habitats where it has naturalised as an introduced species; the ornamental cultivar 'Aureomarginata' is not considered an ecological risk in the same way. Allow at least 1.5 to 2 m in all directions when planting 'Aureomarginata' in a garden border in moist soil, and be prepared for it to spread further.

Q: How do I grow spartina pectinata aureomarginata in the UK?

Spartina pectinata 'Aureomarginata' grows best in a large, open, sunny to partially shaded position in moist to wet, moderately to highly fertile, neutral to slightly acid soil; it is particularly suited to a waterside position (alongside a large pond, a stream, a river, or a large bog garden) where the soil is consistently moist to wet and the rhizomatous spread can be accommodated without conflict with other plantings. Full sun produces the strongest growth, the best gold leaf colour, and the most vivid autumn colour (the leaves colour to shades of orange, gold, and bronze in October and November); partial shade is tolerated but reduces the autumn colour intensity somewhat. Plant from spring to early summer; space at 1.5 m or more apart as the plant spreads widely over time. Keep consistently moist throughout the first growing season to establish the root system; once established, spartina is very drought-tolerant in moist soil positions and requires almost no supplementary watering in a typical UK waterside or bog garden setting. Cut back to 15 to 20 cm in late winter (February to March) before new growth begins, or leave the cut until early spring; the standing stems and leaves provide some structural winter interest and valuable habitat for overwintering invertebrates. Divide overgrown clumps in spring every five to six years by digging out sections of rhizome with a sharp spade; spartina roots are tough and may require significant effort to divide in established clumps. Do not grow in close proximity to smaller plants as the vigorous rhizomatous spread will outcompete them over time.

Spartina pectinata 'Aureomarginata' (variegated prairie cord grass) is a bold, structural ornamental grass with very long, gold-edged, arching leaves to 1.5 m and exceptional autumn colour. Native to moist North American prairies and marshes, it prefers consistently moist to wet soil and spreads vigorously by rhizomes. Leaf curl is almost always a moisture problem: too dry in a well-drained position, or root-damaged in stagnant waterlogged clay.

Drought in dry soil

Spartina pectinata prefers consistently moist to wet soil; in light, freely draining, dry garden soil the long strap-like leaves roll inward along their length and brown at the tips in a hot UK summer. This is a moisture-sensitive plant for a wet position, not a drought-tolerant prairie grass in the way that many other prairie species are. Even a prolonged dry spell in what is normally moist soil can trigger leaf curl in a warm UK summer.

What to do

Grow in a consistently moist to wet position: alongside a large pond or stream, in a bog garden, or in a deep, moisture-retentive border with regular watering in dry spells. In dry UK summers, water deeply and frequently; apply a thick mulch to retain soil moisture. If the position is naturally dry and well-drained, spartina is the wrong choice; substitute with a drought-tolerant ornamental grass (calamagrostis, stippa, or pennisetum) for the same structural effect in dry conditions.

Container moisture stress

Spartina's vigorous, wide-spreading rhizomes and preference for moist conditions make it poorly suited to container growing; containers dry out quickly in warm weather and restrict the root spread. The leaf rolling and tip browning that develops in a container in a hot UK summer is a direct response to moisture stress and root restriction. Very large containers watered extremely frequently can work, but it is a labour-intensive solution.

What to do

Plant in open ground in moist soil for best results; if container growing is required, use the largest possible container (minimum 60 to 80 cm diameter), fill with moisture-retentive loam-based compost, stand in a very large saucer of water, and water daily in warm weather. Consider whether an alternative, more container-suited ornamental grass would better meet the requirement.

Stagnant waterlogging in clay

Although spartina tolerates and prefers wet conditions, stagnant, poorly-oxygenated waterlogging in heavy, compacted clay in high summer temperatures can damage the root system and cause leaf curl and yellowing. The salt marsh habitat of wild spartina has tidal fluctuation; roots are alternately wet and aired. Static clay waterlogging without any oxygen exchange is a different and more damaging condition.

What to do

Improve soil structure before planting in clay by incorporating organic matter; avoid compacting the soil around the planting area. A dynamic waterside position with moving water (stream margin, natural pondside) is better than a static, compacted clay hollow. If the site is very heavy clay, raise the planting height slightly and plant into a mix of topsoil and organic matter to improve aeration around the root zone.

Frequently asked questions

Why are my spartina leaves curling?

Spartina leaves curl most commonly because of drought in dry or well-drained soil (needs consistently moist to wet conditions; water deeply; apply thick mulch; waterside or bog garden position is ideal), container moisture stress (poorly suited to containers; root restriction and rapid drying cause leaf roll and tip browning; open ground in moist soil is far better), or stagnant waterlogging in heavy clay (oxygenated, dynamic wet conditions tolerated; static anaerobic clay waterlogging in summer damages roots; improve soil structure). Consistent moisture is the critical factor.

Is spartina pectinata invasive in the UK?

Spartina pectinata 'Aureomarginata' spreads vigorously by underground rhizomes and will colonise a large area of moist garden soil over time; allow at least 1.5 to 2 m in all directions and be prepared for further spread. Not classified as invasive in the UK (unlike the ecological problem species S. alterniflora in UK saltmarshes) but requires space management in smaller gardens. Install root barriers 50 to 60 cm deep to contain spread, or grow in the largest possible container with very frequent watering.

How do I grow spartina pectinata aureomarginata in the UK?

Grow in a large, open, sunny to partially shaded position in moist to wet, moderately fertile, neutral to slightly acid soil. Waterside, bog garden, or stream margin are ideal. Full sun produces the best gold leaf colour and autumn colour. Plant in spring. Keep moist through the first season. Cut back to 15 to 20 cm in late winter. Divide every five to six years in spring. Give it 1.5 to 2 m space; do not plant near smaller plants it will outcompete.

What is the autumn colour of spartina pectinata aureomarginata?

Exceptional; one of the best ornamental grasses for autumn colour. The long, arching, gold-edged leaves (to 1.5 m) colour to vivid gold, orange, and bronze-orange from October to November. Most vivid in full sun. Lasts into December in mild UK autumns. Combined with the gold-edged summer foliage, 'Aureomarginata' is a year-round structural specimen for a large, moist garden. Scale and impact comparable to large miscanthus cultivars, but better suited to wet conditions.