General
Guelder-rose (Viburnum opulus) is a hardy, native shrub with lacecap-like white flowers in late spring, followed by clusters of glossy red berries that persist into winter and feed birds. The three-lobed leaves color orange to red in autumn. It thrives in moist, fertile soils and tolerates neutral to alkaline conditions. The popular cultivar 'Roseum' (snowball tree) has showy sterile pom-pom blooms but no berries. Flowers are produced on last year’s wood, so heavy pruning in winter reduces next season’s bloom. The berries are mildly toxic raw to humans; some traditional uses involve thorough cooking and straining, but they are primarily valued for wildlife.
Light
Full sun to partial shade; best flowering and fruiting in at least 4–6 hours of sun.
Soil type
Moist, humus-rich loam or clay; tolerates periodic wetness and calcareous soils; good drainage prevents root issues.
Water requirement
Medium to high. Keep evenly moist, especially the first 2–3 years and during summer droughts.
Nutrient requirement
Low to medium. Annual compost mulch is usually sufficient.
Precultivation
This shrub is usually propagated by cuttings rather than seed. For seed, expect morpho-physiological dormancy: warm–cold stratification (e.g., 2–3 months warm, then 3–4 months cold) can take 6–18 months to germinate. Softwood cuttings: take 8–12 cm shoots in early summer, use a free-draining medium, high humidity, and bottom heat around 18–21°C. Hardwood cuttings: take pencil-thick one-year shoots in late autumn to winter, insert outdoors in a sheltered bed or in pots kept cold but not frozen solid.
Planting
Plant container-grown shrubs in spring once daytime temperatures stay above 5°C, or in early autumn while soil is warm. Space 150–300 cm depending on mature size and use (closer for a hedge). Dig a hole twice as wide as the pot, set the plant at the same depth, backfill with native soil improved with compost, water thoroughly, and mulch 5–8 cm while keeping mulch off the stems. Water weekly the first season if rainfall is low.
Pruning
Flowering occurs on old wood. Lightly shape right after flowering (mid-June to July) to avoid removing next year’s buds. In late winter, remove dead, diseased, crossing, or winter-damaged wood. For renewal, every 2–3 years take out up to a third of the oldest stems at the base to encourage vigorous new shoots. Avoid hard pruning in early spring before bloom unless necessary.
Maintenance
Mulch annually with compost or leaf mold to conserve moisture and feed soil life. Water deeply in dry spells; aim for 2–3 cm of water/week in summer if rain is lacking. Feed lightly in spring with compost or an organic, balanced fertilizer; avoid high-nitrogen feeding which encourages lush, pest-prone growth. In calcareous regions, micronutrient issues are rare; in very acidic soils, add garden lime gradually to move toward neutral.
Harvest
If using berries, harvest in early to mid-autumn when fully red and soft; handle with care and cook thoroughly (they are not for fresh eating). Most growers leave the fruit for birds and for winter ornamental value. Flower heads can be cut for arrangements when the outer sterile florets open.
Common issues
Viburnum leaf beetle (Pyrrhalta viburni) can defoliate shrubs. Inspect undersides of leaves in spring; prune out egg-laden twigs in winter; hand-pick or hose off larvae; encourage predators; as a last resort, use organic insecticidal soap or neem targeting early larval stages. Aphids may cause curled leaves—pinch out tips or wash off with water/soap solution. Fungal leaf spots occur in wet summers; improve air flow and avoid overhead watering. Root problems are rare in well-drained but moist soils.
Pollination
Cross-pollinated. Plant at least two genetically distinct Viburnum opulus plants nearby to maximize fruit set (cultivar 'Roseum' is sterile and does not fruit).
Companion plants
Dogwoods (Cornus), elder (Sambucus), hazel (Corylus), willows (Salix), meadow grasses and moisture-loving perennials like Filipendula and Iris sibirica.
Incompatible plants
Drought-loving xeric plants (e.g., lavender, thyme) that prefer dry, lean soils.
