American Mountain Ash (Sorbus americana)

American Mountain Ash

Sorbus americana

Clusters of bright berries glow like tiny lanterns in autumn. Deciduous ornamental tree; common name: American Mountain Ash.

Full sun
1–2/week
Moderate
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Plant Needs

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Sunlight Prefers full sun to partial shade; full sun supports optimal flower and fruit production
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Watering Water deeply when the top 5–7 cm of soil is dry; tolerates short drought periods once established
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Temperature Extremely cold-hardy, withstanding temperatures as low as -40°C; thrives in cool temperate climates
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Characteristics

  • Leaf: Pinnately compound, 15–30 cm long, with 11–17 oval leaflets, serrated margins, bright green turning yellow-orange in fall
  • Flower: Flat-topped corymb clusters of small white, five-petaled blooms
  • Fruit: Dense clusters of bright orange-red pomes, 5–8 mm diameter, persisting into winter
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Care Guide

Watering

Keep soil consistently moist during active growth; avoid waterlogging

Fertilization

Apply balanced slow-release fertilizer once in early spring. Avoid over-fertilizing, as excessive nitrogen can reduce fruiting

Eggshell powder topdress:Crush clean, dried eggshells into fine powder; sprinkle lightly on the soil surface in early spring to boost soil calcium levels without causing nutrient burn
Pruning
  • Remove dead, damaged, or crossing branches in late winter to improve airflow and tree structure
  • Thin crowded inner branches to increase light penetration for better fruiting
  • Trim suckers at the base to maintain tree shape and reduce competition for nutrients
  • Remove any diseased foliage promptly to prevent spread of fungal infections
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Non-toxic to cats; no known adverse effects

Humans: Mild gastrointestinal upset may occur if large quantities of berries are ingested

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Garden Uses & Culture

Culture: Bright winter berries symbolize resilience; provides critical food for overwintering birds

Usage: Ornamental garden tree; wildlife food source for birds and small mammals