Pheasants Forever Nebraska

Problem Trees & Shrubs: Four Methods of Winter Treatment

In prairie ecosystems, upland birds and other wildlife thrive in a diversity of grasses, forbs, and wildflowers for survival and reproduction. Historically, these mesic habitats maintained themselves of woody encroachment through frequent fires and large herding browsers. While fires planned and unplanned still occur, the introduction of invasive trees to originally treeless regions of North America have led to a decrease in quality habitat. Trees and shrubs naturally grow up and out, choking out surrounding competition by blocking sunlight and absorbing nutrients that are necessary for plant growth. If left unchecked, areas once vast and diverse can become limited stands of woody monocultures

 

Around the first week in May my phone will normally be ringing off the hook with questions on how to treat volunteer trees and shrubs. Species that commonly become problematic are Siberian elm (Ulmus pumila), cottonwood (Populus deltoides), green ash (Fraxinus pennsylvanica), silver maple (Acer saccharinum), smooth sumac (Rhus glabra) and eastern red cedar (Juniperus virginiana). While growing season treatments are the most common, getting after these invasive species well after the crops have been harvested into the winter is also an excellent opportunity. To successfully control the problem at hand, knowing a little basic tree biology and growth patterns is crucial to lowering costs and repeated labor.

 

How Trees Work

In essence, a tree is a tall plant, no different from wildflowers and other forbs found on the prairie, but with woody tissue that supports the weight of its crown. During the growing season, energy is transferred from the roots to the shoots, and the leaves convert sunlight, water, and carbon dioxide into nutritional sugars through the process of photosynthesis. This energy is dispersed across the tree for growth in height, diameter, and the formation of seeds or fruit. Leading up to the dormant season, the tree ceases growth and sends some of its energy downwards back to the roots for winter storage.

 

 

Photo Credit: University of Nebraska at Lincoln Extension Tree Identification Manual

When looking at the cross section of a tree (see image on left), the actively growing components are the phloem and the cambium. The phloem can be viewed as a plumbing system for the tree which carries nutrients and sugars from the leaves down the tree through the branches, trunk, and roots. The cambium is the driving force behind increasing the diameter of a tree and is most well-known for creating the annual rings we use to age a fallen tree.

 

Methods of Treatment

To successfully kill a tree, damaging the phloem and cambium of the main stem is essential. While summertime foliar spraying is an easy fix for some, here are four very effective methods of invasive tree control to accomplish over the winter.

 

  1. Photo Credit: Maine Department of Agriculture, Conservation, and Forestry

    Girdling or Cutting – For trees that have no dormant buds located in the trunk, like eastern red cedar and most conifers (evergreens), cutting around the entire diameter and deep enough to sever through the phloem will kill the tree. It is advised that with girdling you make 2 wraparound cuts, 12” apart, below the lowest live branch. If your project calls for early successional woodland habitat – dropping a deciduous tree (tree that sheds leaves annually in the fall) will result in stump sprouts – which can produce favorable cover and woody browse for quail and deer.

    • Tools Required: A handsaw for smaller stems, a chainsaw for larger stems
  2. Photo Credit: Florida State Extension

    “Cut-Stump” – This method is similar to cutting the tree, but with the addition of chemical immediately following the cut. As previously explained, during the dormant season the phloem works to send sap downward towards the roots. By coating an herbicide around the outer ring, the chemical is pulled down through the “tree’s plumbing”, which damages the roots and kills the tree. This method prevents stump sprouts and can be a quick and easy fix to an otherwise expensive problem.

    • Tools Required: Handsaw, chainsaw, or weed eater with a brush blade. Spray bottle or chemical can with paintbrush.
  3. Photo Credit: Florida State Extension

    “Hack-N-Squirt” – Don’t have a working chainsaw? No problem! The same result can be accomplished with a hatchet and a spray bottle or syringe. Although this method can be viewed as more labor intensive, especially in areas with higher densities and smaller stems, it’s a very cost-efficient way of killing off a patch of problem trees. Instead of cutting a complete circle around the tree’s diameter, the hack is made at a 45-degree angle to act as a “cup” which holds the chemical that is squirted in after the cut is made. 1 hack is made for every inch of diameter, so for a 2” wide tree, 2 cuts would need to be made. Ensure that the hacks are below the last live branch, around the trunk, and deep enough to penetrate the living tissue.

    • Tools Required: Hatchet or machete, spray bottle or syringe
  4. Photo Credit: Florida State Extension

    Basal Bark Treatment – Some trees respond negatively to cutting, such as tree-of-heaven (Ailanthus altissima) which is a rapidly growing invasive that is extremely prolific in seed dispersal and its ability to sprout from the stump and roots. This method can be applied on thinner barked trees that are 6” in diameter or less, by utilizing a spray pump mixed with choice chemical and a surfactant to coat the entire base of the tree. Keep the spray intact from the root collar to 24” up the main stem as the absorbed chemical will choke out the vascular system on the tree. It’s recommended that basal bark treatments be avoided if the tree is larger than 6” in diameter, or if snow, ice, or water is on the bark or base of the tree, as the method may not be as effective.

    • Tools Required: Low pressure backpack sprayer or hand-pump sprayer

 

What herbicide do I use for treatments?

The active ingredients in commonly used herbicides for woody control include Glyphosate, Imazapyr, and Triclopyr. But trees respond differently to chemicals used in certain regions. It is advised that you contact your local forester or county extension representative for their recommendation on chemical selection and rates. Safety when mixing and applying should be a number one priority. Be sure to follow all label directions for formulations, rates, and application methods. Wear disposable gloves, eye protection, and rubber boots when the chemical is out, and keep cleaning clothes with water handy in case flushing chemical off is needed.

 

What to do with the trees?

For “basal bark” and “hack-n-squirt” treatments, the tree will die while remaining vertically intact. Standing dead trees, also called snags, offer excellent habitat for wildlife, especially for woodland birds, burrowing mammals, insects, and fungi. Consider leaving smaller snags, but if it poses a risk to other people, livestock, or structures – safely felling and leaving the woody material is a good alternative.

 

For “cut-stump” treatments, trees can be piled and burned with adequate snow cover or surrounding green up. These piles temporarily act as summertime shade or winter cover for upland birds, furbearers, and other wildlife. For simply cutting eastern red cedar trees, take note of unburned piles, as dried out trees become a super volatile source of fuel in the case of a fire (prescribed or wildland).

 

Whether your property goals are to eradicate woody encroachment to stay in CRP compliance, restore your native rangeland from cedars, or you are looking to improve understory growth for wildlife, winter is one of the best times to tackle the project.

About the Author

Rob van Lieshout is an avid outdoorsman who utilizes his background and education in Forestry and Natural Resources Management to work with landowners on improving their wildlife habitat projects. Rob is a Farm Bill Wildlife Biologist II in Nebraska, and he oversees the northeastern counties of Knox, Cedar, and Dixon. He enjoys hunting whatever is in season and processing his successful harvests into table fare.