Winter Pruning of Beverly Hills Oak and Elm Trees

In the charming village of Beverly Hills, Michigan, mature oak and elm trees grace many properties, contributing to the area's lush canopy, property values, and neighborhood character. These iconic trees provide shade in summer, yellow and red fall colors, and habitat for local wildlife. However, they face serious threats from two devastating fungal diseases: oak wilt (caused by Bretziella fagacearum) and Dutch elm disease (caused by Ophiostoma novo-ulmi and related species). Both diseases can be spread overland by insects that are attracted to pruning wounds during the growing season, but winter pruning - when trees, and insects, are dormant - offers a safe, effective way to maintain tree health while minimizing infection risk.

As a resident of Beverly Hills in Oakland County, understanding these diseases and adopting proper pruning practices is an important aspect to protecting oak and elm trees in your landscape.

Oak Wilt and Its Threat to Michigan Oaks

Oak wilt is a vascular disease that blocks water flow in the tree, leading to rapid decline and death. Trees in the red oak group (oaks with pointed leaf tips, such as northern red oak and black oak) are highly susceptible to oak wilt and can die within weeks to months of infection. Trees in the white oak group (oaks with rounded leaf tips, like white oak and bur oak) are more resistant and may survive longer but can still succumb over years.

Oak wilt fungus spreads to trees in two main ways:

• Overland, via sap-feeding nitidulid beetles (also called picnic beetles) that carry spores from oak wilt fungal mats on infected trees to fresh wounds on healthy oaks.
• Underground, through root grafts between nearby oaks.

In Michigan, oak wilt has been widespread since the mid-20th century, with ongoing detections being confirmed in the Lower Peninsula, including areas near Oakland County. The highest-risk period for new infections in Beverly Hills is April 15 through July 15, when beetles are most active and spore mats are abundant. Pruning, storm damage, or any wound during this window can invite infection.

Winter pruning eliminates this risk entirely. During the dormant season (typically November through March in southeast Michigan), beetles are inactive due to cold temperatures. This makes winter the ideal and safest time to prune oaks, according to the Michigan Department of Natural Resources (DNR) and Michigan State University Extension. Plan major pruning, trimming for clearance, or removal of hazardous limbs now, before spring arrives.

Dutch Elm Disease and the Need for Dormant-Season Care

Dutch elm disease (DED) has a tragic history in Michigan, having devastated American elm populations since the mid-20th century. The fungus clogs the tree's vascular system, causing wilting, yellowing leaves, and eventual death of the entire tree. It spreads primarily via elm bark beetles that carry spores and through root grafts with nearby infected elms.

While resistant hybrid elms are now available and increasingly being planted, many legacy American elms remain in Beverly Hills landscapes. Pruning wounds attract beetles, especially during warmer months when they are active (roughly mid-spring through fall). To prevent spreading Dutch elm disease, experts recommend pruning elms only during tree dormancy - typically October through March - when beetles are inactive.

In some Michigan communities, ordinances restrict elm pruning to winter periods below 40°F to avoid beetle activity. While Beverly Hills' tree ordinance focuses on prohibited species and requires permits for certain work in public rights-of-way, it underscores the village's commitment to tree health. Always check with the Village of Beverly Hills Department of Public Services before major pruning on trees in public right-of-ways.

Why Winter Pruning Benefits Both Tree Health and Disease Prevention

Pruning during dormancy offers multiple advantages:

• Disease avoidance - No active vectors (insects) to spread oak wilt or DED.
• Better healing - Trees focus energy on wound closure as soon as growth resumes in spring.
• Structural improvements - Easier to see branch structure without leaves; remove dead, crossing, or hazardous limbs safely.
• Overall vigor - Promotes better airflow and light penetration in the tree canopy and reduces storm damage risk.

For oaks and elms, aim to complete work by mid to late March to avoid the approaching highest-risk period for oak wilt or Dutch elm disease to spread.

Best Practices for Professional Winter Pruning

Always hire an ISA Certified Arborist experienced with these diseases. In Beverly Hills, local professionals familiar with Oakland County conditions can ensure compliance with village rules and proper techniques. Key tips include:

• Use clean, sanitized tools (a bleach solution works to prevent any residual spread).
• Make proper cuts just outside the branch collar.
• Remove debris promptly - do not leave wood with the bark attached on-site if diseased.
• For confirmed infections, consult experts for trenching (to break root grafts), fungicide trunk injections, or other disease management options.

Preserving Beverly Hills' Tree Heritage

By scheduling pruning in winter, Beverly Hills residents can protect valuable oaks and elms from oak wilt and Dutch elm disease while enhancing tree longevity and beauty. These proactive steps support the village's green legacy, prevent costly removals, and maintain the shaded streets and landscapes we all enjoy.

If you're noticing wilting, branch dieback, or other symptoms, contact an ISA Certified Arborist promptly for diagnosis. With informed care, our community can keep these magnificent trees thriving for generations.