Rock Elm

Ulmus thomasii

Native to:
Canada, United States

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Taxonomy

Division:
Magnoliophyta | - Flowering plants
Family:
Ulmaceae
Genus:
Ulmus
Species:
Ulmus thomasii
USDA Symbol:
ULTH

Growth Characteristics

Life Cycle:
Perennial
Growth Habit:
Tree
Height:
2100 cm
Light Requirements:
Full Sun,Part Shade,Shade
Drought Tolerance:
Medium
Bloom Months:
mar,apr,may
Bloom Colors:
green

Wildlife Benefits

Caterpillars:
★☆☆☆☆ Recorded caterpillar host plant (HOSTS Database)

Keystone Species Ranking

Caterpillar Keystone:
★★★★★ Butterfly & moth species supported by this genus (NWF)

Host Plant for Caterpillars

Canadian Melanolophia (Melanolophia canadaria), Cecropia moth (Hyalophora cecropia), Imperial Moth (Eacles imperialis), Theisoa constrictella

Garden & Ecology Notes

Wildlife Value:
birds, small mammals
Fall Color:
yellow

Soil Requirements

Soil Type:
rich, well-drained loamy soil
pH:
6.0 - 8.0 (slightly acidic to neutral)
Drainage:
tolerates moderate drainage
Moisture:
dry to moderate
Notes:
Prefers calcareous soils; often found on limestone outcrops

Propagation & Germination

Stratification:
Cold/moist stratification required — 60–90 days
Germination Time:
14–28 days
Notes:
Seeds are short-lived and should be sown fresh. Cold stratification improves germination rates.

The above propagation data sourced from Claude AI

Pre-treatment: Cold-moist stratification for 30 days at 1–5°C (34–41°F).; then Cold-moist stratification for 60 days.

Source: Claude AI