Oaks: bur oak and English oak

Botanical names

Quercus macrocarpa (bur oak); Quercus robur (English oak)

Type

Long-lived deciduous shade trees

Size

Large and broad; bur oak can reach about 130 feet in its home range (USDA Forest Service)

Hardiness

Bur oak zones 2 to 8; English oak zones 4 to 8; zones 6b to 7b here

Where it is found

Large lots and parks on the valley floors, about 4,000 to 5,100 feet

Known weak points

Heavy limbs, acorn litter, soil compaction and construction damage

A mature oak in a valley yard is often the oldest living thing on the block. Utah State University rates both species high for alkaline soil, and bur oak high for drought. This page covers identification, where they grow by elevation and when pruning, cabling or removal is right.

How do you identify bur oak and English oak?

Bur oak leaves are large, six to ten inches long, with five to nine rounded lobes, and the acorn cup covers at least a third of the nut. Bark is thick, gray-brown and deeply grooved. English oak leaves are smaller, two and a half to five inches, with an earlobe-like base and a short stalk. The acorn hangs on a long stalk one to three inches long.

In winter both have a spreading, coarse crown of stout limbs. Shape helps too: English oaks come in narrow and wide forms, and bur oaks have a broad canopy.

• Bur oak: large leaves with 5 to 9 rounded lobes
• English oak: smaller leaves with earlobe bases, acorns on long stalks
• Thick, deeply grooved bark
• Stout, spreading limbs

Where does it grow in Reno, Carson City and the Carson Valley?

Both oaks are rated hardy enough for every ZIP we serve, from Reno (4,505 feet, zone 7b) and Carson City (4,680 feet, zone 7a) to Minden (4,725 feet, zone 6b) and Incline Village (6,437 feet, zone 6b). Utah State rates bur oak high for drought and says it handles heat, cold and wind; English oak prefers well-drained soil and rates medium for drought.

Utah State lists both as not native to Utah, and in our valleys they are planted trees rather than wild ones. At Tahoe elevations they are uncommon, and the lot trees are conifers.

What goes wrong with it here?

Utah State lists few pests for bur oak, and the Forest Service says mature bur oaks are rarely damaged by fire because of their thick insulating bark. The usual trouble is not disease. It is weight and site: large limbs over a roof, soil compacted by construction and acorns that drop on cars and paths. Oaks that have lost root area to trenching or fill show dieback in the crown; see root and trunk decay.

The same thick bark that protects them also hides trouble. Cracks at a union, a cavity or mushrooms at the base are reasons for an inspection; see warning signs of tree failure. Both oaks are rated not good under power lines.

Pruning, cabling or removal: which is the right call?

Dead and hanging wood can be taken out any time. For other pruning the usual window is late winter, while the tree is dormant. On an old oak the cuts are small and deliberate; you do not thin a mature oak heavily or reduce it by large cuts. Oaks do not respond well to topping.

A strong oak with a weak fork or a split limb is a good candidate for cabling and bracing, since the rest of the tree is worth holding together. Removal is the answer when the trunk is hollow or the roots are failing, or when a large dead limb hangs over a structure. A big oak is often a crane-assisted removal job.

What does Battle Born Tree Service do about an oak?

The free estimate is where this gets decided. We assess the tree in person, and the arborist's call is one of careful pruning, cabling or removal. We hold a Nevada Business License (#20131580674) and are fully insured, and two of the eight crew members are ISA Certified Arborists (WE-11728A is one person's credential). For firewood, call the office for availability and pricing.