Welcome to the City of Evansville, Department of Urban Forestry page

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Having problems with these?  Horned Oak Galls...


Here is some information about the galls and what to do about them:
• Horned Oak Galls (Cynapid wasp galls) are more numerous in Pin Oaks and Shingle Oaks this year than ever before. We are not 100% why, but are speculating that the reason is due to the drought 2 years ago…trees were placed under stress in 2012 drought, and while still under stress last year, were infested by wasps (trees under stress are usually attacked more by insects/disease than healthy ones), then galls began to develop late last year, and are now fully developed and very noticeable. We are hoping that, since we have had 2 decent growing seasons now, that the galls will not be as prevalent in the future. >>>go to this link to see more information on galls<<<
• Galls are caused by a very small wasp that is harmless to humans called the cynapid wasp. This wasp lays it’s eggs in the stem of the tree, which creates a growth, looking like a ball. Over the next year, the gall will form and eggs will hatch from it and new wasps will emerge and the cycle will continue.
• Usually trees will not die, but some trees may get overburdened with them, and if they do, and die as a result, it is likely due to other stress factors in addition to galls, such as lack of water, poor soils, compacted soils, lack of root space, etc. With this said, again, we have never seen this many galls in oaks as ever before, so it is possible we could be looking at loosing more than we normally do in a given year due to galls.
• These galls only grow on Oaks in the Red Oak group, but are more common on Pin Oaks and Shingle Oaks, which is why we have those two species on our do not plant list.
• There are many reports of debris falling to the ground from the trees. What is happening is, squirrels are eating the galls and causing remnants of the galls to fall to the ground and twigs and bunches of leaves. Since the galls will end up killing the stem they are on and the leaves attached to the stem, the squirrels are actually not hurting the trees by doing this. if anything, they are likely benefiting the trees. so we are not recommending people to try to keep squirrels out of trees. Unfortunatly, this is causing many peoples lawns/driveways/streets to look a bit messy, even after cleaning them up after one day. Since this is a naturally occurring issue, there is no way to resolve this particular issue appropriately, except bear through it.
• There are no known treatments that work to kill the wasps or keep them from affecting trees.>>>see study in this link<<<
• Since no known treatments work, we can only recommend people try to keep their trees healthy by properly watering them once per week during dry periods to keep them healthy in hopes that it will help the trees withstand the added stress from the galls.>>>Go to this link to see how to properly water trees<<<


Upcoming events:

Ordinance Compliance Seminar - Tree Pruner's (Arborist) Licensing

Dates & Time: Feb 12, May 14, Aug 13, Nov 12, each @ 6pm central time.

Cost: FREE (Must Bring Picture ID)  Length: 4 hours

Location: Wesselman Woods Nature Center

Description:  Seminar required for obtaining Tree Pruner's license. >>>click here to see how to obtain and maintain a license<<<


Do you need to hire someone to prune or remove a tree?

For a person/business to prune or remove trees for hire within the city of Evansville, on public or private property, they must have a license.  What does it mean if the company does not have a license?  It may be that they do not have the appropriate insurance.  Click >HERE< to get a list of licensed tree companies.  Please remember that the list is updated routinely.  For more information on hiring a tree company click >HERE<.  Click the International Society of Arboriculture link below to do a search for Certified Arborists.  If you are a tree company and need to get a license, call our office at 436-5752.



 Publications about trees & how to care for them

Accomplishments & Future Goals Reports - See what our department has accomplished, and what we plan on doing in the near future.  Includes a list of tree work preformed by Department of Urban Forestry.

2009, 2010, 2011, 2012, 2013

Watering Trees - It's not as simple as you may think...check out this helpful tree watering guide.

Planting Trees A document that describes how to select the right tree for the right place, and how to properly plant them.

Why Not to Top Trees - 8 reasons why not to top trees and alternatives to topping.

Construction, Development, & Trees - Description of how development/construction can harm trees, and how to preserve trees during development.

Benefits of Trees in Business/Commercial Districts

Arboricultural Specifications Manual - Tree planting, pruning, & care specifications for city owned trees in Evansville.  Includes lists of acceptable and unacceptable trees.

About our Department...

The Evansville Department of Urban Forestry is under the Department of Transportation and Services, and consists of four full time tree crew workers, and is managed by the Evansville City Arborist. The duties of the Department of Urban Forestry are as follows:

  • Enforcement of the Evansville Tree Ordinance.
  • Accomplishes the day to day activities of hazardous tree and tree limb removal.
  • Removal of tree debris created by storms.
  • Inventory of existing public trees.
  • Supervision of the Arborist Licensing program.
  • Presentation of tree related materials to public.
  • Development and dissemination of educational brochures pertaining to trees.
  • Inspection and recommendations for public tree issues.
  • Dissemination and review of public tree planting and removal permits.
  • Planning, performing, and assistance for public tree planting.
  • Recertification for Tree City USA status & Growth Award.
  • Planning and supervision of annual Arbor Day event.
  • Coordination with other government agencies, not-for-profit groups, and the public concerning tree related activities issues.
  • Apply for Grants.

Tree Advisory Board

The Evansville Tree Advisory Board meets the first Thursday of the month at 8am, in room 318 of the Civic Center.  Special meetings, or a change of location will be announced here in the future.  If you would like to have an agenda, or would like to be on the agenda, please call 475-1426.


Evansville Tree Ordinance - regulates the appointment and activity of the Tree Advisory Board, pruning and care of trees on public property, tree pruner's licensing requirements, and other public tree concerns.


Related Links

Go to the GIS Mapping Website - Shows street and park trees, forested areas, parks, nature areas, champion trees, and canopy cover in Evansville.

International Society of Arboriculture - This site can be used to look up Certified Arborists, and professional arboricultural standards.

National Arbor Day Foundation - Includes information about the Tree City USA program, Growth Award, and other tree related information.

Purdue Department of Forestry and Natural Resources Urban forestry Section

Purdue University Publications - This is a link to a great number of FREE publications available on-line from Purdue University.

Indiana Community & Urban Forestry - Lists programs, publications, and other information about urban forestry in Indiana.

Southwest Indiana Master Gardener Association - upcoming events, classes, programs, and activities sponsored by the Master Gardeners.

National Big Tree Register - List of the largest known tree of each species in the US.  This list is maintained by American Forests.  Can you find the two national champion trees in Evansville in the list?

Indiana Big Tree Register- List of the largest known tree of each species in Indiana.  There are 26 in Vanderburgh County!

Emerald Ash Borer (EAB) - See where EAB currently is, and other information about the pest.

Keep Evansville Beautiful - This is a not-for-profit organization that is beneficial for programs such as Anti-Litter campaigns, Adopt-A-Spots, and of course, our annual Arbor Day event.

Wesselman Nature Society - The site is linked to Wesselman Woods Nature Preserve & Center, Howell Wetlands, and Canoe Evansville.  Wesselman Woods is a natural gem in the city containing many wonderful trails and champion trees!

Pigeon Creek Greenway - Instrumental not-for-profit group that has dedicated towards the completion and improvement of our local Greenway trail system through the city.

Indiana Arborist Association- Link to other Professional Arborists in Indiana.

Contact us at...

1000 Oak Hill Road                 
Evansville, IN 47711
Phone: (812) 436-5752
Fax: (812) 436-5748

City Arborist: Shawn Dickerson

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Last updated: 7/8/2015 7:28:32 AM