Plant problems

Why Are My Cortaderia Leaves Curling?

Q: Should I cut back my pampas grass in the UK?

Cutting back Cortaderia selloana (pampas grass) in late winter or early spring (late February to March) is the standard and most widely recommended management practice for pampas grass in a UK garden; it improves the appearance of the plant by removing the dead, curled, brown outer leaves that accumulate through winter, allows light and air to reach the growing centre of the clump, and stimulates vigorous new leaf and plume production through the following growing season. The two accepted methods of cutting back are: burning (the traditional method, in which the dead outer leaves of the clump are set alight with a torch or lighter in late winter on a calm day, burning off the dead material quickly and cleanly while leaving the growing centre undamaged; this is effective and fast but is subject to obvious safety concerns in a domestic garden and may be prohibited or inadvisable in dry conditions, in proximity to other vegetation, or where it is incompatible with neighbouring properties or local fire regulations; it should only be carried out on a completely calm day with water available); and cutting back by hand (cutting the entire clump of leaves back to a manageable height of 30 to 50 cm above ground level using heavy-duty loppers, shears, or a reciprocating saw or hedge trimmer for the largest, most established clumps; cutting back by hand is the safer method but the sharply serrated leaf blades of cortaderia are genuinely dangerous — always wear thick gloves, protective clothing covering the arms and legs, and safety glasses or a face shield when cutting back pampas grass, as the leaf edges can cause deep cuts). Both methods are effective; the key is to carry out the work in late winter or very early spring before new growth begins, and to wear appropriate protective equipment. Do not cut back in early winter as this reduces the plant's protection from winter cold.

Q: Is cortaderia selloana invasive in the UK?

Cortaderia selloana (pampas grass) is not classified as an invasive species in the UK under the Wildlife and Countryside Act 1981 or the Invasive Alien Species (Enforcement and Permitting) Order 2019, and it does not appear on the UK Schedule 9 list of invasive non-native plants that it is illegal to plant or encourage to grow in the wild. In contrast, Cortaderia selloana (and the closely related C. jubata) are classified as significant invasive species in New Zealand, California, Hawaii, parts of Australia, and several other warm-climate regions where the combination of mild, wet winters, warm summers, and the absence of the insects and pathogens that control it in its native South American range has allowed it to naturalise and spread aggressively on roadsides, coastal cliffs, wasteland, and disturbed ground; it self-seeds prolifically in these climates and is considered a serious environmental weed displacing native vegetation. In the UK, the cooler, more variable climate and the shorter, less reliable warm season mean that self-seeding and naturalization of pampas grass outside the garden are uncommon or sporadic; plants in UK gardens generally do not spread invasively into the wider environment, and the species is not considered to present the same invasive risk in the UK climate that it does in California or New Zealand. Gardeners in the UK can grow pampas grass without the ecological concerns that apply in other parts of the world, but should be aware of its potential in milder climates if plants are placed close to boundaries or natural areas, and should avoid disposing of divisions or cuttings where they could establish in the wild. Cortaderia jubata (purple pampas grass) is on the UK Schedule 9 list and should not be planted.

Q: How do I care for pampas grass in the UK?

Caring for Cortaderia selloana (pampas grass) in a UK garden involves the following: Planting: plant in full sun in a freely draining, moderately fertile soil; pampas grass tolerates most UK soil types including clay, loam, sandy, and chalk soils once established, but performs best on soils that are not waterlogged in winter (excessive winter waterlogging is more damaging than cold alone in UK conditions); plant in spring or early summer for best establishment; the plant grows slowly in its first one to two years but accelerates significantly in years three to five and beyond. Position: full sun is essential for best plume production; in partial shade the plant produces fewer and smaller plumes and a less compact growth habit. The mature clump can reach 2 to 3 m in height including the plumes and 1.5 to 2 m in spread; allow adequate space. Cutting back: cut back to 30 to 50 cm in late February to March using heavy-duty loppers or shears; always wear thick gloves and protective clothing as the leaf edges are sharply serrated and can cause deep cuts. Watering: water regularly in the first growing season after planting; established plants are drought-tolerant and rarely need irrigation. Feeding: top-dress with a balanced general fertiliser in spring; avoid excessive nitrogen, which produces lush, floppy leaf growth at the expense of plume production. Division: established clumps can be divided in spring but are very vigorous and difficult to split by hand without power tools; the sharply serrated leaves require full protective clothing and the root system is dense; division is usually only necessary when a clump has become very large or has developed a dead centre.

Cortaderia selloana (pampas grass) is a large, vigorous ornamental grass grown for its dramatic white or pink silky plumes in late summer and autumn. The long, arching, sharply serrated leaves curl from drought stress or dry soil, insufficient sun, or cold and wind damage in winter. Annual cutting back in late February to March is the key maintenance task.

Drought and dry soil

Although drought-tolerant once established, pampas grass on a dry, sandy, or chalk soil in a drought year shows leaf curl along the length from the tips downward, beginning at the outer leaves of the clump, with the tips browning and becoming papery. New plantings are most vulnerable in their first two to three seasons before an extensive root system develops. Established, large clumps on heavier, more moisture-retentive soils are significantly less affected.

What to do

Water new plantings regularly through the first growing season; once established (after two to three years), pampas grass rarely needs irrigation in the UK even in dry summers. On very freely draining sandy or chalk soils, incorporate organic matter at planting and mulch the base to retain moisture in the first few years. Established clumps showing drought curl typically recover fully as conditions improve; the outer curled leaves can be removed as part of the annual late-winter cut-back.

Insufficient sun

Pampas grass requires full sun for best growth and plume production; in partial or dappled shade the leaf blades become thinner, weaker, and more prone to flopping outward, and the number and size of plumes is significantly reduced. The upright, architectural character of a well-grown pampas grass in full sun is replaced by an open, floppy, sprawling clump with fewer plumes in shaded conditions. In deep shade the outer leaves yellow and curl rapidly.

What to do

Plant in the sunniest available position; pampas grass needs at least six hours of direct sun per day for best plume production. If an existing plant is shaded by surrounding vegetation that has grown up since planting, removing or reducing the shading plants (where practical) will improve growth and plume production. Avoid planting in the shade of buildings, walls, or trees; a large, open, sunny site is ideal.

Cold and wind damage

Cortaderia selloana is generally frost-hardy in the UK, but in particularly cold or wind-exposed winters the outer leaves of the clump may brown, curl, and die back. This winter leaf damage is primarily cosmetic; the growing point at the centre of the clump is usually undamaged in UK winter conditions. The annual cutting back in late February to March removes this damaged material and allows clean new growth to emerge.

What to do

Do not cut back pampas grass in early winter; the dead outer leaves provide some insulation to the growing centre through winter. Cut back in late February to March (before new growth begins) to 30 to 50 cm above ground level using heavy-duty loppers or shears. Always wear thick gloves, protective clothing covering arms and legs, and safety glasses; the sharply serrated leaf edges can cause deep cuts. The plant responds vigorously to the annual cut-back with strong new leaf and plume growth through summer.

Frequently asked questions

Why are my cortaderia leaves curling?

Cortaderia leaves curl most commonly because of drought and dry soil (drought-tolerant once established but curls from the tips down on dry, sandy, or chalk soils in drought years; water new plantings regularly for the first two to three years; established clumps recover as conditions improve; remove curled outer leaves at annual cut-back), insufficient sun (full sun required for best plume production; partial shade produces floppy, thin leaves and fewer, smaller plumes; six hours direct sun minimum), or cold and wind damage (outer leaves may brown and curl in exposed winters; growing centre usually undamaged; cut back in late February to March; wear thick gloves and protective clothing). Annual late-winter cut-back is the key maintenance task.

Should I cut back my pampas grass in the UK?

Yes; late February to March is the standard time. Two methods: burning (fast, effective, obvious safety concerns; calm day only, water available; do not burn near other vegetation or in dry conditions) or cutting back by hand (heavy-duty loppers, shears, or reciprocating saw/hedge trimmer for large clumps; cut to 30 to 50 cm above ground; ALWAYS wear thick gloves, protective clothing covering arms and legs, and safety glasses; the serrated leaf edges cause deep cuts). Both methods stimulate vigorous new growth. Do not cut back in early winter as this removes winter insulation from the growing centre.

Is cortaderia selloana invasive in the UK?

Not classified as invasive in the UK; not on Schedule 9 of the Wildlife and Countryside Act. In contrast, C. selloana and the closely related C. jubata are significant invasive species in New Zealand, California, Hawaii, and parts of Australia where they self-seed prolifically and displace native vegetation. UK cooler climate makes self-seeding and naturalization uncommon or sporadic; the species does not present the same invasive risk as in warmer climates. Gardeners can grow pampas grass without the ecological concerns that apply in California or New Zealand. Note: Cortaderia jubata (purple pampas grass) IS on the UK Schedule 9 list and should not be planted.

How do I care for pampas grass in the UK?

Plant in full sun in freely draining, moderately fertile soil; tolerates clay, loam, sandy, and chalk soils once established; avoid persistent winter waterlogging. Allow 1.5 to 2 m spread; matures to 2 to 3 m including plumes. Water regularly in the first growing season; established plants are drought-tolerant. Top-dress with balanced fertiliser in spring; avoid excess nitrogen (produces floppy leaf growth at expense of plumes). Cut back to 30 to 50 cm in late February to March wearing thick gloves and protective clothing. Division possible in spring but vigorous and difficult; only necessary for very large or dead-centred clumps.