Alpine cudweed: complete guide

Overview

Omalotheca supina, commonly known as alpine cudweed or dwarf cudweed, is a low-growing, mat-forming perennial in the family Asteraceae, formerly classified under the genus Gnaphalium as Gnaphalium supinum. It is native to the mountains and high-altitude grasslands of Europe, Central Asia, the Caucasus, and northern North America, with a distribution spanning Scandinavia, the Alps, the Pyrenees, the Carpathians, the Urals, and extending across Russia to Mongolia, Iran, and Greenland. In Europe it is found in Germany, Austria, Switzerland, France, Norway, Sweden, Finland, Great Britain, and many other countries, typically at elevations of 1200 to 3000 metres above sea level.

The species epithet supina refers to its prostrate to low-lying growth habit, which is an adaptation to the windswept, exposed conditions at high altitudes where the plant must stay below the wind and utilise the warmth retained by rocky substrate. This growth strategy is shared with many other alpine cushion plants but Omalotheca supina is particularly distinctive with its soft, white-woolly leaf undersides and small cream-white flower heads.

For specialist gardeners interested in authentic alpine plantings, rock gardens with acid substrate, or naturalistic heath and moorland compositions, Omalotheca supina offers genuine botanical interest alongside a quiet decorative appeal. Its ecological niche is narrow but well-defined, and replicating its preferred conditions in a garden setting is achievable with the right substrate and positioning. Design your alpine or acid garden layout at [gardenworld.app](https://gardenworld.app) to explore how specialist mountain plants like this one integrate into cohesive plantings.

Appearance & bloom cycle

Omalotheca supina grows as a tight, ground-hugging rosette and mat typically reaching only 5 to 15 cm in height. The leaves are narrow, spatulate to lanceolate, 1 to 3 cm long, green on the upper surface and densely coated with white woolly hairs on the underside, giving the plant a silvery appearance when the leaves are turned by wind or examined closely. This indument — characteristic of the Gnaphalium-alliance genera — is a functional adaptation reducing water loss through transpiration in the windy, high-UV conditions of mountain environments.

Stems are decumbent to ascending, also densely hairy, and form a compact carpet over time. In early spring the rosettes are fresh and green; from July through September the plant produces flowering stems 8 to 15 cm tall bearing small, cylindrical flower heads with membranous, light-brown to whitish phyllaries surrounding the tiny disc florets, which are white to cream in colour. The heads are clustered in dense terminal corymbs, modest in appearance but botanically typical of the tribe Gnaphalieae.

The bloom period runs from July to September. After pollination — primarily by small hover flies and specialist alpine insects — small achenes with a white pappus of silky bristles develop, enabling wind dispersal in late August and September. The dried flower stalks remain briefly before the plant settles back into its basal rosette form for winter. The silvery-textured rosettes are visually attractive even outside the flowering season, catching and holding morning dew or frost crystals in a way that gives the plant a luminous quality in low light.

Ideal location

In its natural mountain habitat, Omalotheca supina receives intense but relatively brief solar radiation in an open, fully exposed position on alpine grassland, scree, or rocky ridgelines. In garden conditions, this translates to a full sun position with at least six hours of direct sunlight daily, ideally on a south or southwest-facing aspect. The position must be completely open — any overhead shading from trees or large shrubs will cause the plant to become drawn and eventually decline.

Excellent drainage is non-negotiable. The ideal position is a raised rock garden, an alpine trough, a sloped scree bed, or a raised border where water drains freely away from the root zone at all times. The root collar must never sit in standing water, even briefly. A gentle slope of at least 10 to 15 degrees encourages natural drainage and mirrors the mountain slope conditions the plant is adapted to.

For flat, lowland gardens where natural drainage is limited, the most reliable approach is growing Omalotheca supina in purpose-built hypertufa or stone troughs filled with a specialist alpine mix, placed on a sunny terrace or patio. This allows precise control of both soil composition and drainage. A pane of glass or Perspex propped above the trough during prolonged wet periods in winter prevents root collar saturation — in the mountains, the plant overwinters under dry snow rather than wet rainfall, and replicating that dry-cold winter condition is key to long-term success.

Soil requirements

Soil is the most critical factor for growing Omalotheca supina successfully. It requires a distinctly acid substrate with a pH of 4.5 to 5.0 — considerably more acidic than the majority of garden plants. On neutral or alkaline soils it will show stress symptoms, fail to thrive, and eventually die. This is not a plant for chalk gardens, limestone rock gardens, or soils enriched with lime-containing compost or chalk-based mulch materials.

The ideal growing mix combines: 40% coarse granite or quartzite grit, 30% gritty acid loam or heath soil, 20% sphagnum peat or coarse ericaceous compost, and 10% perlite or pumice for additional aeration. This blend is nutrient-poor, fast-draining, and acidic — mimicking the thin, leached mountain soils of the alpine zone. Do not incorporate general garden compost, spent mushroom substrate (which is alkaline), or animal manure, all of which alter pH in the wrong direction.

Top-dress annually in early spring with a thin layer of coarse granite or quartzite gravel. This keeps the root collar dry, reflects light upward to the underside of the leaves, and maintains the acid, mineral character of the surface layer. Use only inert siliceous aggregates — never limestone chippings or shell grit, which raise pH with every rain event.

Watering

Omalotheca supina has a paradoxical water relationship: it grows in mountain regions with high annual precipitation, yet is adapted to conditions where water drains instantly from the rocky substrate and roots never remain saturated. The rule in cultivation is: water freely but allow the substrate to dry out quickly between waterings.

During the growing season (April to September), water whenever the top 1 cm of the mix feels dry — typically two to three times per week in warm, dry weather. Short periods of drought are tolerated far better than prolonged wetness. Use rainwater or softened water if possible; hard tap water progressively raises the soil pH and will gradually harm the plant over multiple seasons. The difference is noticeable within two or three growing seasons on acid-sensitive species like this one.

Winter watering is the most critical management challenge, particularly in lowland garden conditions. In the mountains the plant is protected by dry snow cover that insulates the roots from fluctuating temperatures while keeping the substrate dry. In lowland winters with alternating mild, wet periods and cold spells, persistent moisture around the root collar combined with temperature oscillation around freezing point causes far more damage than cold alone. Protect the plant from winter rain with a glass or Perspex pane propped above it, or move container specimens to a cold frame or alpine house.

Pruning

Omalotheca supina requires minimal pruning. Its naturally low, compact, mat-forming growth habit means no clipping is needed to maintain shape. The only regular task is removing dead or damaged flower stalks after they dry out in September and October, cutting them back cleanly to the basal rosette level. Leave the rosette leaves intact — they overwinter and provide the growth base for the following year.

If the mat becomes very dense or the central rosettes show signs of die-back after several years, carefully lift outer rosette sections in early spring (March or April) and replant them in fresh acidic alpine mix. This rejuvenates the central plant and provides propagation material. Handle the plant gently as the woolly leaves bruise easily, and any damage combined with high humidity can allow Botrytis (grey mould) infection to take hold.

In autumn, remove any accumulated dry leaf litter that may have blown into the mat — decomposing organic matter raises local pH and creates conditions conducive to fungal problems. Do not apply a thick mulch directly onto the rosette; a collar of coarse inert grit around but not over the crown is the correct approach.

Maintenance calendar

February–March: Assess winter condition. Remove dead material. Check substrate pH; correct if above 5.5 by incorporating ericaceous compost or sulphur. Remove winter rain protection once the hardest frosts are past.

April–May: Plant resumes active growth. Ensure drainage is unrestricted. Water with softened water if dry. Watch for slugs on new growth in wet, mild springs.

June: Growth accelerates. Water regularly but allow drying between sessions. First flower buds may appear on early specimens.

July–September: Blooming period — small cream-white flower heads decorate the mat. No special care needed. Continue watering with rainwater or soft water.

October: Remove dried flower stems. Add a thin top-dressing of coarse granite grit around the rosette. Consider placing rain protection in position for wet winters.

November–January: Minimal maintenance. Protect from prolonged winter rain in lowland settings. Do not fertilise. The plant overwinters as a semi-dormant or evergreen rosette.

Winter hardiness

Omalotheca supina is exceptionally frost hardy — one of the most cold-tolerant plants in cultivation. It survives temperatures far below -20 °C and is rated to USDA hardiness zone 3, covering the harshest regions of Scandinavia, Northern Canada, and continental Russia. In the Netherlands, Belgium, the UK, Germany, and France, cold temperatures in winter present no danger whatsoever to this species.

The challenge in lowland winter conditions is not cold but wet. The plant evolved under dry snow cover that protects the root zone from temperature swings while keeping it dry. In typical Western European winters, with alternating mild wet spells and brief cold snaps, persistent moisture around the root collar — particularly on poorly drained substrates — causes crown rot that kills the plant far more readily than any frost. On a well-drained acid substrate in a raised or sloped position, winter losses are rare. In flat, poorly drained settings, winter rain protection with a glass cover or alpine house placement makes the difference between reliable survival and losses.

Container-grown plants in troughs on exposed terraces are slightly more vulnerable than border-planted specimens because the small soil volume cools more rapidly and dries out less predictably. Move trough specimens to a sheltered but unheated position if temperatures are expected to remain at -10 °C or below for extended periods.

Companion plants

For authentic alpine garden compositions, pair Omalotheca supina with other species that share its need for acid, nutrient-poor, freely drained substrate and full sun:

• Silene acaulis (moss campion): tight green cushions with pink flowers in spring, identical pH and drainage requirements (pH 4.5–6.0), natural companion on alpine rock and scree.
• Saxifraga oppositifolia (purple mountain saxifrage): early-flowering, vibrant purple, grows on acid rocky substrate in similar mountain zones.
• Vaccinium myrtillus (bilberry): low semi-woody shrub with acid soil requirements (pH 4.5–5.5) and berry-bearing interest in late summer.
• Calluna vulgaris (heather): shares acid-peat substrate requirements exactly, blooms August–September simultaneously with Omalotheca.
• Deschampsia flexuosa (wavy hair-grass): graceful acid-soil grass that adds movement and texture to the planting.
• Empetrum nigrum (crowberry): evergreen, low-growing acid-soil shrublet with small dark fruits, extending the visual season.
• Minuartia verna (spring sandwort): white-flowered cushion-former for acid scree, very similar ecological niche.

Avoid mixing with lime-tolerant or neutral-soil plants such as Lavandula, Achillea, or Sedum album, whose soil-pH preferences are incompatible with the strongly acid conditions Omalotheca supina requires.

Conclusion

Alpine cudweed is not a plant for the impatient or for gardeners seeking instant, showy impact. It is a botanical specialist from the world's harshest mountain environments, carrying millennia of adaptation to conditions that would destroy most garden plants. Grown correctly — in a full sun, freely drained, strongly acid substrate — it rewards the specialist gardener with a beautiful silver-textured mat that blooms reliably each July through September and endures decade after decade.

For advice on designing an alpine or acid garden that incorporates specialist mountain plants like Omalotheca supina alongside complementary heathers, saxifrages, and grasses, visit [gardenworld.app](https://gardenworld.app) and create a personalised planting plan suited to your garden's conditions.