White Alder (Alnus rhombifolia)

White Alder

Alnus rhombifolia

Its diamond-shaped leaves catch sunlight like scattered coins. Deciduous tree; common name: White Alder.

Full sun
1–2/week
Beginner
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Plant Needs

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Sunlight Full sun to partial shade; tolerates dappled shade in woodland settings
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Watering Drought-tolerant once established; water deeply during dry spells, avoid overwatering
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Temperature Hardy to -10°C; tolerates hot summer temperatures up to 35°C; avoid prolonged severe frost
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Characteristics

  • Leaf: Diamond-shaped, glossy green upper surface, paler underside, serrated margins
  • Flower: Male catkins are long, drooping; female catkins are small, upright, cone-like
  • Stem/Bark: Smooth gray bark when young, becoming fissured with age; slender, branching stems
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Care Guide

Watering

Water deeply every 7–10 days during extended dry periods

Fertilization

Optional light compost topdressing to support growth. No regular fertilization required due to nitrogen-fixing root nodules

Composted banana peel tea:Use fully composted banana peels, steep in water for 24 hours, dilute 1:20 for root drench; avoid raw peels to prevent pest infestations
Pruning
  • Remove dead or damaged branches in late winter to improve airflow
  • Thin crowded inner branches to enhance light penetration through the canopy
  • Shape young trees to establish a strong central leader for structural stability
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA-verified non-toxic to cats

Humans: No known toxic effects on humans

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Garden Uses & Culture

Culture: N/A

Usage: Soil stabilization along waterways; ornamental shade tree; nitrogen-fixing to improve soil fertility