Gambel oak: the neighbor everyone asks about

The neighbor on the bench is not in the table. USU NR/FF/002 (Mike Kuhns, February 2005) opens with a photograph captioned House in dense Gambel oak stand. No plant is fireproof. The firewise tree rows are Acer, Betula, Cercis occidentalis, Populus tremuloides, other Populus, and Salix. Quercus gambelii is not in that table. USU Forestry identification: the common scrub oak along the foothills of the Wasatch is fire-prone on native sites and should be thinned around buildings. White, Weise, Mackes, and Dibble 2002 Table 4 (GOAK): 107% moisture, green peak heat release 41 kW/m², dry effective heat of combustion 14.2 MJ/kg. This directory currently computes the species as on-list, limited-evidence, and includes UT.

You are on a Salt Lake bench treating the oak clone as a Firewise native because the leaves look like a deciduous hardwood. Kuhns put the house in the oak in the photograph and left the species off the list. The 2002 cone number is foliage, not a thicket against the siding.

This is not a Utah doorway. Utah WUI code status is the 2006-now / 2024-in-2027 construction book. It does not rate the oak.

Why it matters

Bench lots sit in Gambel oak because that is the foothill vegetation. Embers do not care that the oak is native. USU’s firewise sheet is a placement and maintenance list. USU’s tree page and 2021 landscape sheet are a stand-structure warning. The lab row is a foliage measurement. Those three sentences can all be true. Zone 0 is still not a planting list.

This site’s Utah plant evidence combines 432 occurrence records with 83 exact USU source owners. Occurrence is not Kuhns’s table, and table membership is not site suitability.

How it works

What USU actually printed (NR/FF/002, February 2005):

• Author: Mike Kuhns, State Extension Forester. Utah Forest Facts NR/FF/002.
• Caption on the first photograph: House in dense Gambel oak stand.
• Firewise plants coupled with design and maintenance help establish defensible space. Plants alone do not guarantee fire safety.
• Native vegetation can be managed by pruning, thinning, and occasional clearing.
• No plant is fireproof. All will burn in a very intense fire.
• All trees provide large amounts of fuel. Broadleaved trees generally are less flammable than conifers (pines, firs, spruces, junipers).
• Don’t assume a relative of a listed plant is firewise.
• Tree rows: maple, birch, California redbud, quaking aspen, other poplar/cottonwood, willow.
• This directory stores that sheet as the usu-kuhns lineage (83 plants or plant groups; listed = recommend). Utah FFSL’s later Firewise Landscaping for Utah book is the same lineage, not a second vote. See the Steward rule.

What USU says about the oak itself:

• Identification page: common scrub oak along the Wasatch foothills. Clumps, dense pure stands, vigorous root sprouts after fire. Fire-prone on native sites; thin around buildings to reduce fuel. Can reach 60 feet.
• Gambel Oak in the Landscape (Shawn Olsen and Debbie Amundsen; revised September 2021 by Shital Poudyal): dry slopes and canyons 3,000–8,000 feet; Wasatch Front zone 5; 20–30 feet typical. Spreads by lignotubers or rhizomes into dense continuous vegetation. Fuel hazard from dense stands and horizontal continuity. Higher during drought and in late summer or fall when the leaves are dry. Adapted to moderate fire; resprouts, sometimes in the same season. Thin: prune or mow sprouts; cut the top quarter; heavily thin the canopy at 12–15 feet interval.

What the cone calorimeter measured (Colorado sampling, 25 kW/m²):

• GOAK green PHRR 41 kW/m², lowest in Table 4 (group E). Moisture 107%. Dry EHOC 14.2 MJ/kg.
• The two junipers, lodgepole pine, and Douglas-fir had significantly higher dry EHOC than gambel oak, chokecherry, snowberry, and mountain mahogany.
• That is a foliage specimen in a sample holder. It is not a Wasatch clone field.

This directory:

• Quercus gambelii on-list, limited-evidence, UT. The recommend lineage is White 2002 (author-named low relative flammability). Idaho Firewise is stored as mixed, score 6 of 10, placement 50 feet from the home. Mixed is not a second recommend vote. See what limited evidence means.
• Populus tremuloides on-list, UT, and on Kuhns’s tree list (needs supplemental moisture; young clumps).
• Acer grandidentatum on-list, UT. Kuhns lists Acer as a genus, not this species by name. Do not assume a relative is listed. The species vote here is PNW 590 and other rows on the plant page, not NR/FF/002.
• Juniperus scopulorum avoid, UT.
• Artemisia tridentata avoid, UT.

See how to read a plant page. Direct fire evidence is never silently outvoted by a list. The reverse is also true: a low green PHRR does not erase a dense stand. When the lab disagrees with the lists is the juniper version of that rule.

Utah WUI code status: 15A-2-103 currently names the 2006 Utah Wildland Urban Interface Code for local adoption. The 2024 IWUIC is effective 1 January 2027. Salt Lake City 18.44.010.B adopts the book 15A-2-103 names. That calendar does not rewrite Kuhns.

The paths

What people mix up

• Native Wasatch oak with on the USU firewise table. It is in the photograph. It is not in the tree rows.
• A low green PHRR with safe against the siding. Idaho’s stored row already says 50 feet. Zone 0 is still empty.
• Limited-evidence as “the lab was weak.” The stack is thin. Table 4 is not.
• Idaho’s mixed 6-of-10 as a second Steward vote beside White 2002.
• Acer on Kuhns’s list as a listing of Acer grandidentatum. Kuhns warns against assuming relatives.
• Utah juniper in White 2002 (Juniperus monosperma, UJUN) as this oak. Different species, opposite end of Table 4 (228 kW/m²).
• The 2027 code date as a new plant list.
• 432 USDA rows as FFSL’s planting list.
• FEIS Quercus gambelii (not opened this session) as quoted.

How to check

1. Open NR/FF/002. Read the oak-stand caption, no plant is fireproof, and the tree rows.
2. Open USU Gambel oak. Read fire-prone on native sites and thin around buildings.
3. Open Gambel Oak in the Landscape. Read 12–15 feet and lignotuber resprout.
4. Open the 2002 PDF. Table 4, GOAK, 41 kW/m², 14.2 MJ/kg.
5. Open Quercus gambelii. Read on-list, limited-evidence, Idaho 50 feet.
6. Open Utah plant evidence.
7. Do not plant in Zone 0.

Limits

This page quotes the opened February 2005 NR/FF/002 PDF, the live USU tree-identification HTML, the September 2021 landscape HTML, and the opened White 2002 PDF. The May 2010 HTML twin of NR/FF/002 was opened and matches the table and caption; dates in the article use the PDF’s Published February 2005. Idaho Firewise PDF was not re-opened this session; the 6-of-10 and 50-foot figures are the stored evidence row on the plant record. FEIS Quercus gambelii (Simonin 2000) was not opened. Utah FFSL’s 2007 Firewise Landscaping for Utah book was not opened; it is the same usu-kuhns lineage. 432 is a count of stored USDA-distribution rows as of this writing. 83 is the stored plant-source count of Kuhns groups, not a recount of PDF lines this session. Zone 0 is not a planting list.

Related records

• Quercus gambelii
• Populus tremuloides
• Acer grandidentatum
• Juniperus scopulorum
• Artemisia tridentata
• Utah plant evidence
• Utah WUI code status
• When the lab disagrees with the lists
• What limited evidence means
• How to read a plant page
• Fire-resistant is not fireproof
• The Steward rule
• Zone 0