rock elm
Ulmus thomasii · Ulmaceae
rock elm (Ulmus thomasii) is a perennial tree in the Ulmaceae family. It is native to North America. USDA records it as hardy in zone 2 and warmer, down to about -46°F.
At a glance
| Type | tree USDA |
|---|---|
| Lifecycle | perennial USDA |
| Native status | native USDA |
| Mature height | 90 ft USDA |
| Light | part-shade USDA |
| Water need | high USDA |
| Growth rate | moderate USDA |
| Soil pH | 4.5–7.2 USDA |
| Bloom | April–May USDA |
| Flower color | Yellow USDA |
| Hardiness zones | 2 and warmer USDA |
| Guild layer | canopy Derived |
| Nursery availability | No Known Source USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It grows in partial shade. USDA rates it as having needs consistently moist ground. It is recorded on soils from pH 4.5 to 7.2 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 2; USDA publishes no warm-end limit, so gardeners in warmer zones should check local heat tolerance separately.
Size and growth
At maturity it reaches about 90 ft, making it a large tree that will dominate its site. It grows at a moderate rate, which matters when you are timing a planting around the layers above it.
Bloom period
USDA records a bloom period of April through May. The flower color USDA records is yellow. Bloom timing is how the Guild Builder overlaps flowering across a planting so something is in flower for as much of the season as possible.
Bloom period is a claim about when this plant flowers. It is deliberately not a pollinator rating — no dataset we trust publishes one, so we do not make that claim. See Data & sources.
Role in a guild
Canopy. In a layered planting this is the tallest layer of a planting — it sets the light budget everything beneath it lives on. We derive the layer from the plant's growth habit and mature height using a fixed rule, so the same inputs always produce the same layer.
Tags
Related plants
Others in Ulmus
- winged elm Ulmus alata
- American elm Ulmus americana
- cedar elm Ulmus crassifolia
- Chinese elm Ulmus parvifolia
Similar role and hardiness
- boxelder Acer negundo
- red maple Acer rubrum
- silver maple Acer saccharinum
- bitternut hickory Carya cordiformis
- black ash Fraxinus nigra
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol ULTH, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
bloom_end— quoted from USDA PLANTSbloom_start— quoted from USDA PLANTScommercial_availability— quoted from USDA PLANTSduration— quoted from USDA PLANTSflower_color— quoted from USDA PLANTSgrowth_habit— quoted from USDA PLANTSgrowth_rate— quoted from USDA PLANTSguild_role— derived by rule from USDA columnsmature_height_ft— quoted from USDA PLANTSmoisture— quoted from USDA PLANTSnative_status— quoted from USDA PLANTSnitrogen_fixer— quoted from USDA PLANTSpet_safe— quoted from USDA PLANTSph_max— quoted from USDA PLANTSph_min— quoted from USDA PLANTSshade_tolerance— quoted from USDA PLANTStemperature_min_f— quoted from USDA PLANTSzone_min— quoted from USDA PLANTS
Read our full data sources and methodology.
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