Plant problems

Why Are My Andropogon Leaves Curling?

Q: Will andropogon gerardii grow well in the UK?

Andropogon gerardii (big bluestem) can grow well in the UK in the right conditions — a warm, open, sunny position in freely draining, moderately fertile, neutral to slightly acid soil — but it is more climate-sensitive in the UK than some other prairie grasses; its performance is most reliable in the warmest UK regions (south and south-east England, sheltered midlands gardens) and in warm, sunny UK summers. In a warm UK summer in the right position, andropogon produces an impressive structural plant to 1 to 1.5 m with attractive blue-green and purple-tinged summer foliage and a good autumn colour display of copper and burgundy-red; in a cool UK summer or in northern UK regions, the plants may be shorter, less colourful, and less vigorous. The autumn colouring is the primary ornamental feature in the UK and is most vivid after a warm UK summer in a fully sunny, well-drained position. Compared with the related schizachyrium scoparium (little bluestem), andropogon is larger, more imposing as a specimen or back-of-border structural plant, but also more demanding of warmth and space. In a prairie or meadow-style planting in a large, sunny UK garden, andropogon can be a magnificent structural grass; in a small or shaded garden, schizachyrium or panicum 'Shenandoah' would be better choices for similar colour effects at a more manageable scale.

Q: How do I grow andropogon in the UK?

Andropogon gerardii grows best in a warm, fully sunny position in moderately fertile, freely draining, neutral to slightly acid soil; it tolerates a broader range of soil conditions than schizachyrium (including moderately moist, deep prairie-type soil) but does not tolerate persistently waterlogged or very wet conditions, particularly in winter. Full sun is essential. Plant in spring (April to May) to allow a full growing season of establishment before the first winter; andropogon is slow to establish in its first year and the full ornamental display typically develops from the second or third year. Water through the first growing season; once established, moderately drought-tolerant, though it performs better with occasional watering in very dry UK summers than some other prairie grasses. Do not feed in rich soil (lean soil produces better colour and structure); a single spring feed of balanced fertiliser can help in very poor, thin soils. Cut back to 15 to 20 cm in late February or early March before new growth begins; the dry, copper-coloured stems provide a good structural winter feature. Fully hardy in the UK in well-drained conditions, tolerating temperatures to approximately -20°C; very cold combined with wet winter conditions is the greatest risk to UK survival. Divide every five to six years in spring if the clump becomes very congested.

Q: What is the difference between big bluestem and little bluestem?

Andropogon gerardii (big bluestem) and Schizachyrium scoparium (little bluestem) are both iconic North American prairie grasses with similar blue-green summer foliage and spectacular copper-orange to burgundy-red autumn colour, but differ significantly in scale and some characteristics. Big bluestem (andropogon) reaches 1.5 to 2 m in height in warm conditions (1 to 1.5 m in the UK) with broader, more substantial leaves to 60 cm and a more imposing structural presence; it is better suited to larger gardens as a structural back-of-border or specimen grass. Little bluestem (schizachyrium) is much more compact at 60 to 90 cm, with narrower leaves and a neater, more vase-shaped form suited to smaller gardens, mixed borders, or large containers. Both require full sun and freely draining soil. Both have exceptional autumn-to-winter colour, but the autumn colour of big bluestem tends toward warm copper-orange with burgundy-red highlights, while little bluestem often produces more vivid, intense burgundy-red to orange-copper tones. The seed heads differ: big bluestem has the distinctive 'turkey foot' three-branched seed head cluster; little bluestem has numerous smaller, fluffy, silver seed heads along the stems. For most UK gardens of average size, little bluestem (schizachyrium) is the more practical and manageable choice; for a large, prairie-style planting or as a bold structural specimen, big bluestem (andropogon) provides greater scale and impact.

Andropogon gerardii (big bluestem, turkey foot grass) is the iconic grass of the North American tallgrass prairie, reaching 1 to 1.5 m in the UK with blue-green, red-tinged summer foliage that colours to vivid copper and burgundy-red in autumn. Full sun and freely draining soil are essential; waterlogging and shade are its main problems in UK cultivation. Slow to establish but magnificent from the second or third year.

Waterlogging and wet soil

Andropogon is a deep-rooted prairie grass that tolerates moderately moist conditions but fails in persistently waterlogged or wet UK garden soil, particularly through winter. In heavy, poorly draining clay, the characteristic blue-green and purple-tinged foliage turns yellow, curls, and browns as root function is impaired. Cold wet conditions through winter are a particular risk to UK survival.

What to do

Grow in freely draining, deep, moderately fertile soil in full sun. In heavy soil, incorporate organic matter and coarse grit at planting to improve drainage and aeration; a raised bed is a reliable option in clay gardens. Avoid positions that pool water in winter. Unlike some prairie grasses, andropogon tolerates moderately moist (but not wet) soil in summer, so it can succeed in a range of UK border soils provided winter drainage is adequate.

Too much shade

Full sun is essential for the characteristic blue-green, red, and purple-tinged summer foliage and for the copper and burgundy-red autumn colour. In partial shade, the tall stems become floppy, the foliage colour washes out, and the autumn display is muted; the plant leans toward the light rather than standing upright. In deep shade, andropogon fails within one to two seasons.

What to do

Plant in a fully open, unshaded position; south or south-west facing in the most open part of the garden. The tall stems can be an advantage in a back-of-border position in full sun, providing a structural backdrop for shorter prairie perennials and grasses in front. In a garden with limited sun, schizachyrium (little bluestem) at 60 to 90 cm is a more compact option with similar colour effects.

Insufficient summer heat

Andropogon gerardii is a warm-season grass that needs warmth to develop its full height and colour; in cool UK summers it typically reaches 1 to 1.5 m rather than the 2 m or more of warm North American climates. The autumn colour is most vivid after a warm UK summer. First-year plants are always disappointing; the full display develops from the second and third years as the deep root system establishes.

What to do

Accept the slow start; do not remove or replace first-year plants that look underwhelming. Grow in the warmest, most sheltered, sunniest position available. In cool UK regions, andropogon may be shorter and less vivid than in warmer UK climates; schizachyrium scoparium or panicum virgatum 'Shenandoah' are more reliably impressive at smaller scale across a wider range of UK conditions.

Frequently asked questions

Why are my andropogon leaves curling?

Andropogon leaves curl most commonly because of waterlogging or wet winter soil (prairie grass; tolerates moderately moist but not persistently wet conditions; incorporate grit and organic matter; raised bed in clay), too much shade (full sun essential; floppy stems and washed-out colour in shade; autumn display muted; open south-facing position needed), or insufficient summer heat (warm-season grass; slow to establish in first year; full display from second and third years; warmest available position). Drainage and full sun are the two requirements.

Will andropogon gerardii grow well in the UK?

Yes in the right conditions: warm, open, sunny, freely draining. Best in south and south-east England and sheltered midlands gardens in warm UK summers. Typically reaches 1 to 1.5 m in the UK versus 2 m in warmer climates. Autumn colour of copper and burgundy-red is the primary ornamental feature and most vivid after a warm UK summer in full sun. More imposing than schizachyrium at a larger scale; for smaller gardens, schizachyrium or panicum are more practical. Display improves significantly from the second and third year.

How do I grow andropogon in the UK?

Grow in a warm, fully sunny position in moderately fertile, freely draining, neutral to slightly acid soil. Tolerates moderately moist (but not wet) soil better than some prairie grasses. Plant in spring. Water through first season. Single spring feed of balanced fertiliser in very poor soil. Cut back to 15 to 20 cm in late February. Fully hardy in well-drained conditions. Divide every five to six years in spring. First-year plants are disappointing; the full display develops from the second and third years.

What is the difference between big bluestem and little bluestem?

Andropogon gerardii (big bluestem) reaches 1 to 1.5 m in the UK; broader leaves; imposing structural back-of-border or specimen grass; distinctive 'turkey foot' three-branched seed head; copper-orange and burgundy-red autumn colour. Schizachyrium scoparium (little bluestem) is compact at 60 to 90 cm; narrower, neater vase shape; more vivid and intense burgundy-red to orange-copper autumn tones; fluffy silver seed heads. For most UK gardens of average size, little bluestem (schizachyrium) is the more practical choice; big bluestem for larger prairie plantings or structural specimens.