September Elm (Ulmus serotina)

September Elm

Ulmus serotina

Its late autumn blooms add soft, leafy warmth to the season. Deciduous hardwood tree; common name: September Elm.

Full sun
1–2/week
Moderate
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Plant Needs

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Sunlight Full sun to partial shade; blooms most profusely in full sun, tolerates moderate shade
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Watering Water deeply during prolonged dry spells; established trees have moderate drought tolerance
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Temperature Hardy to -20°C; tolerates summer temperatures up to 35°C; avoid prolonged extreme cold below -25°C
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Characteristics

  • Leaf: Ovate to oblong leaves 7–15 cm long, with double-serrated margins, dark green upper surface, and pale pubescent underside
  • Flower: Small greenish-yellow perfect flowers in dense clusters, blooming after full leaf emergence
  • Stem/Bark: Young stems have fine pubescence; mature bark is gray-brown with shallow, irregular fissures
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Care Guide

Watering

Water deeply every 7–10 days during dry periods to support new growth

Fertilization

Apply balanced slow-release fertilizer in early spring before new growth. Use a low-nitrogen fertilizer to promote healthy canopy growth without excessive vegetative spread

Banana peel compost tea:Compost banana peels for 4–6 weeks, dilute 1:20 with water for root drench; avoid raw peels to prevent pest infestations
Pruning
  • Prune dead, damaged, or crossing branches in late winter to early spring before new growth emerges
  • Thin crowded inner branches to improve airflow and light penetration through the canopy
  • Remove basal suckers regularly to maintain a single-trunk tree form
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Toxicity

Warning: this plant may be toxic.

Pets & Humans

Pets: ASPCA: Non-toxic; no adverse effects from ingestion

Humans: No known toxic effects from ingestion or contact

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Garden Uses & Culture

Culture: N/A

Usage: Ornamental shade tree for parks and residential landscapes; wood used for furniture and flooring