Plant problems

Why Are My Elymus Leaves Curling?

Q: Why are my elymus leaves curling?

Elymus (blue lyme grass or lyme grass) leaves curl along their length and lose their characteristic steel-blue colour most commonly in UK gardens because of drought stress (Elymus magellanicus and E. hispidus, the species most commonly grown for ornamental blue foliage, prefer moderately moist, freely draining soil; the broad, flat, intensely blue-glaucous leaves curl inward when the root zone dries out, and in container-grown specimens or very sandy soils in a hot UK summer this can be rapid and dramatic), too much shade (elymus foliage colour is produced by a waxy, glaucous coating on the leaf surface that develops most intensely in full sun; in a shaded position, the blue colour fades toward grey-green and the leaves become floppier and more prone to curling and lodging), or the plant becoming too congested in a container or restricted position (elymus is a running grass with spreading rhizomes; in a container or confined bed, the rhizomes fill the available space and the resulting root-bound clump produces increasingly poor, curling, yellowing growth as the root system exhausts available nutrients and moisture). Elymus magellanicus (Magellanic rye grass or blue wheatgrass, from South America) and Elymus hispidus (intermediate wheatgrass) are among the most intensely blue-foliaged grasses available to UK gardeners; the almost metallic, steel-blue colouring of the broad, flat leaves is unique among UK-hardy ornamental grasses and makes them exceptionally striking in a gravel garden or as an accent plant against dark foliage.

Q: Is elymus hardy in the UK?

Elymus magellanicus and E. hispidus are both reliably hardy throughout the UK, tolerating temperatures well below -15°C in freely draining conditions; they are essentially fully hardy in all UK garden situations and require no winter protection. The challenge with elymus in UK cultivation is not cold hardiness but rather the loss of ornamental quality over time: the brilliant blue foliage colour is most vivid in young, fresh growth and fades as the season progresses; the leaves become tatty, straw-coloured, and collapsed by late summer; and the running rhizomes spread the plant beyond its intended position if not regularly divided or contained. For this reason, elymus is often best treated as a short-term display plant that is divided and refreshed every two to three years rather than a permanent specimen. Cutting the plant back hard to the crown in late summer or early autumn (after the seed heads have been enjoyed if desired) stimulates a fresh flush of vividly blue new leaves that look good through autumn and winter; this management approach maintains the plant in its most ornamentally effective state.

Q: How do I grow elymus in the UK?

Elymus grows best in a warm, open, full-sun position in freely draining, poor to moderately fertile, neutral to slightly alkaline soil; the most intensely blue foliage colour is produced in lean, dry, sunny conditions. In rich, fertile, moist soil, the growth is lush and green rather than glaucous blue, and the ornamental effect is much reduced. A gravel garden, raised bed with gritty, lean soil, or a front-of-border position in a sunny, dry, free-draining border is ideal. For E. magellanicus, grow in containers (at least 25 to 30 cm diameter) using a very free-draining, lean compost to maintain the blue colour and to prevent the running rhizomes from spreading freely into the garden; divide and repot every two years in spring. Water only during prolonged dry spells; overwatering in rich soil promotes green, floppy growth and dilutes the blue colour. Cut back hard to the crown in late summer (August to September) to stimulate a flush of vivid new blue growth through autumn. The blue colour is most vivid in spring on fresh new growth; divide the clump every two to three years and replant the most vigorous blue sections in refreshed, lean soil. Install a rhizome barrier or grow in a container if unwanted spreading is a concern.

Q: What is the bluest ornamental grass for UK gardens?

Several ornamental grasses are grown for their blue-grey foliage in UK gardens, and the choice of 'bluest' depends partly on the intensity of colour and partly on the scale and habit of the plant required. Elymus magellanicus (Magellanic rye grass) is one of the most intensely blue ornamental grasses available, with broad, flat, almost metallic steel-blue leaves; it is a low to medium clump (to about 30 to 40 cm in leaf) but has a running habit that requires management. Helictotrichon sempervirens (blue oat grass) is similar in colour intensity but forms a tighter, non-running clump to about 40 to 60 cm in leaf with elegant, arching growth; it is arguably the better garden plant for most situations because it does not run. Festuca glauca cultivars (blue fescue) are smaller (15 to 25 cm) with fine, needle-like blue leaves and a tight, non-running clump habit; the cultivar 'Elijah Blue' is one of the most reliably vivid. Leymus arenarius (blue lyme grass, a close relative of elymus) is a very strongly running species with broad, blue-grey leaves to 60 to 90 cm that is effective in large spaces but highly invasive. For most UK gardens, Helictotrichon sempervirens or Festuca glauca 'Elijah Blue' offer the best blue foliage in a manageable, well-behaved clump.

Elymus magellanicus (blue lyme grass) is one of the most intensely blue ornamental grasses available for UK gardens, with broad, flat, almost metallic steel-blue leaves. Fully hardy but best treated as a short-term display plant divided every two to three years to maintain the vivid colour. The blue fades in shade and rich soil; drought causes curling; running rhizomes require management. A late-summer hard cut stimulates vivid new blue growth through autumn.

Drought stress

Drought causes elymus leaves to curl inward along their length; the broad, flat, glaucous leaves lose their characteristic flatness and roll as the plant loses water-pressure in the leaf tissue. Container-grown elymus and those in very sandy, free-draining soils in a hot summer are most vulnerable. Leaf curl from drought is reversible with watering, but sustained drought causes browning at the tips and margins that does not recover.

What to do

Water during prolonged dry spells, particularly for container-grown specimens; check containers daily in hot weather and water when the top few centimetres feel dry. In-ground plants in a reasonable UK soil rarely need supplementary watering except in exceptional drought. Paradoxically, elymus grown in lean, dry conditions produces better blue colour than plants in moist, rich soil; aim for soil that approaches dryness between waterings but does not desiccate completely.

Too much shade or rich soil

The intensely blue-glaucous colour of elymus leaves depends on a waxy leaf coating that develops most strongly in high light intensity and lean soil conditions; in shade or rich, fertilised soil, the blue fades to grey-green and the leaves become floppier and more prone to curling and lodging. This colour fade is the most common disappointment with elymus in UK garden conditions where plants are grown alongside regular garden plants in fertile, mulched borders.

What to do

Grow in full sun in lean, low-fertility, freely draining soil; avoid mulching with compost or feeding with nitrogen-rich fertilisers. A gravel garden or raised bed with gritty, poor soil maintains the best colour. If the plant has faded in a shaded or fertile position, cut it back hard to the crown, move to a sunnier, leaner site, and allow fresh growth to develop in better conditions.

Root congestion

Elymus has spreading rhizomes that fill available space rapidly; in a container or confined bed, the root-bound clump exhausts nutrients and moisture and produces increasingly poor, yellowing, curling growth as the season progresses. A congested container clump also begins to spread from drainage holes or over the pot rim as the rhizomes seek more space. Division is the solution: the most vigorous outer sections of a divided clump always produce the best, most vividly coloured new growth.

What to do

Divide every two to three years in spring; lift the entire clump, split into sections (each with several strong shoots and attached rhizome), and replant the most vigorous sections in fresh, lean soil or refreshed container compost. Discard old, congested central sections. In open borders, install a rhizome barrier or check annually for spreading beyond the intended area and cut back rhizomes with a sharp spade.

Frequently asked questions

Why are my elymus leaves curling?

Elymus leaves curl most commonly because of drought stress (broad leaves curl inward when roots dry out; water during dry spells; container plants most at risk), too much shade or rich soil (colour fades to grey-green and leaves flop; grow in full sun in lean, gritty, low-fertility soil; avoid nitrogen feed), or root congestion in a container or confined bed (exhausted, yellowing, curling growth; divide every two to three years in spring; replant vigorous sections in fresh lean soil). Cut back hard to the crown in late summer to stimulate a flush of vivid blue new growth.

Is elymus hardy in the UK?

Elymus magellanicus and E. hispidus are fully hardy throughout the UK, tolerating well below -15°C. No winter protection is needed. The ornamental challenge is not cold hardiness but maintaining vivid blue colour (best in full sun, lean soil, regular division) and managing the running habit. Cut back hard in late summer to refresh the foliage; divide every two to three years to maintain vigour and colour intensity.

How do I grow elymus in the UK?

Grow in full sun in poor to moderately fertile, very freely draining, neutral to slightly alkaline, gritty soil. Rich soil produces green, floppy growth. Water only in prolonged dry spells. Cut back hard to the crown in late August to September to stimulate vivid new blue growth through autumn. Divide every two to three years in spring; replant the most vigorous outer sections in refreshed lean soil. Install a rhizome barrier or grow in a container (at least 25 to 30 cm) if spreading is a concern.

What is the bluest ornamental grass for UK gardens?

Elymus magellanicus is among the most intensely blue but has a running habit requiring management. Helictotrichon sempervirens (blue oat grass) is similarly blue, forms a neat non-running clump to 40 to 60 cm, and is arguably the better garden plant for most situations. Festuca glauca 'Elijah Blue' is smaller (15 to 25 cm) with fine needle-like leaves and a tight non-running habit, ideal for edging. Leymus arenarius is very strongly running with broad blue-grey leaves and suits large spaces only.