ProHort Update for May 2026

1. Plant Trees Correctly

Trees are very important to our world. They help with landscape aesthetics, shade, food production, wildlife habitat, and much more. Now is a great time to plant a tree. Correct planting and post-planting care will ensure a long-lived tree for your clientele. 

Diversity

Deciding what tree to plant is very important and can be a difficult decision for your clientele because there are so many trees to choose from. Help your clients choose diversity in their tree selection. Remind clientele to look around their own yard and the neighborhood to ensure the same species are not overplanted. Try to stick to no more than 5% from any one genus in the area to reduce potential pest problems through all the trees in the area.  

Correct Planting

The most important factor to keep in mind when planting trees is planting it correctly to ensure healthy growth. First of all, remove all of the burlap and any other materials from the root ball before planting. Also remove any tags, twine, or wire from the tree. Remember to remove all the grass and weeds that are within the area you will be planting the tree. 

Once you have found the roots of the tree, dig a hole that is 2-3 times wider and no deeper than the root ball and loosen up the sides of the hole. Do not loosen up the bottom of the planting hole, this can cause the tree to end up too deep in the ground. Trees planted too deeply will not develop a root flare and will likely die within 10-15 years following planting. Plant the tree so that first lateral roots are just below the soil surface. 

Finally, backfill with the existing soil that was removed when the planting hole was dug. Do not amend the soil with peat moss, compost or planter box mix that is in the hole, this can lead to circling and girdling roots. Make sure that the entire root ball is covered with soil to avoid drying out. Lightly push on the soil around the root ball, do not tamp down on the soil too hard or it can compact the soil pores and reduce space for water and oxygen to move around the roots. 

Care of Trees

A mulch ring should be established and maintained around every tree. Mulch helps to keep the roots cool in the summer and regulated to a uniform temperature through the winter. Mulch will also help keep weeds down and reduce competition of water and nutrients from turf and other plants. Mulch also reduces damage to the trunk of trees from lawn mowers and trimmers. Finally, organic mulch is a way to hold moisture for use later by the tree. Mulch rings should be only 2-3 inches deep and in a circle around the tree at least 2-3 feet out. Organic mulches are a better choice than inorganic mulches. This mulch will need to be renewed every year to maintain an effective layer because it will break down over the growing season which will improve the soil. Mulch should be placed starting 4-6 inches away from the trunk and extended as far into the landscape as is practical.

Keep the roots of newly planted trees well-watered; moist, not soggy or dry. Always water newly planted trees, shrubs, or any other plant immediately after planting. This allows soil to settle and helps avoid roots drying out. You may need to slice the soil in around the roots as the water infiltrates around the rootball.

Trees should be watered every 7-14 days throughout the growing season and less often during the winter on warmer days. Each watering should be a slow irrigation that allows moisture to infiltrate the soil to the bottom of the roots. Use a soaker hose wrapped around the tree, a small sprinkler, or a hose on a slow trickle in the middle of the drip zone of the tree. The best way to determine if a tree needs to be watered is to insert a soil probe or 12-inch-long screwdriver into the ground around the tree. If it goes in easily there is no need to water, if it is difficult at any point then water is necessary. 

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2. April 29th growing degree days (GDD)

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3. Pest Update 

For a more complete list, visit Michigan State University GGD of Landscape Insects or GGD of Conifer Insects.

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4. Increased Tick Exposure, Nebraska Extension

Green industry professionals are at an increased risk of tick exposure due to frequent work in grassy, brushy, and wooded environments. 

To reduce the risk of tick bites, wear long-sleeve shirts and pants when possible, use EPA-registered repellents, and consider treating clothing and gear with permethrin. Tucking pants into socks and performing regular visual checks throughout the workday can also help prevent ticks from attaching.

The University of Nebraska Medical Center offers free tick pathogen testing across the state, which can be a useful tool for understanding which diseases ticks in your area may carry. However, this service is intended for surveillance purposes only and should not be used for medical diagnosis. If you experience symptoms following a tick bite, consult a healthcare provider promptly. If you are interested in submitting a tick for testing, visit the Nebraska Tick Testing webpage for more information. Nebraska Extension also offers tick identification services at no cost.

The most effective way to prevent tick-borne illness is to perform a thorough, full-body tick check as soon as possible after working outdoors. Prompt and proper removal of attached ticks significantly reduces the likelihood of disease transmission. For more information on how to properly remove ticks, tick bite prevention tactics, and symptoms of tick-borne illness to look out for, visit our Tick Tag Go webpage.

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5. Potting Soil for Patio Planters - Is it Simple or Complex? 

Many landscapers care for front door and patio planters for their clients as well as other plants. Just like ground beds of perennials and annuals, one of the keys to success is the quality of the medium where the roots will take hold. There are many factors involved in choosing and using a quality potting soil, such as age, drainage potential and the various possible components to utilize.  

Read the full article from Greenhouse Product News here

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6. Frost Damage on Tree Leaves

Many homeowners are noticing damage to newly emerged leaves on many trees. Leaves of trees including ginkgo and hackberry had young leaves that developed brown or black tips and edges. This is likely due to the multiple nights of frost or nearly freezing temperatures. Many of our trees had just begun pushing new leaf growth when the cold temperatures hit. This new growth wasn’t mature enough to deal with the unusual quick drop in temperatures that we had. Give the trees time and they will push new growth, while many will drop those damaged leaves. 

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7. Stem Girdling Roots (SGRs)

SGRs are a serious problem for trees. They lead to slow or stunted growth, increase a trees susceptibility to pests, and may lead to wind throw. SGRs develop when young trees are grown in smooth plastic containers or when the roots are not spread out hortizontally when they are planted. Young roots grow quickly and when a root touches the side of a smooth pot it begins to circle around the outside of the root ball. Even field grown trees are often started in pots, so investigate closely to find SGRs that developed when trees were young.

To help avoid SGRs, consumers should select smaller trees, those with a 2 inch or smaller trunk diameter. Trees purchased in grow bags, RootMaker® pots, or other containers designed to minimize circling roots are wise choices. Grow bags are made of fabric which traps the tip of a new root, preventing it from circling. Once the root tip stops growing, additional branching develops along the length of the root resulting in a denser, fuller root system overall. RootMaker® pots are design to air prune roots to prevent them from circling.

If a tree is purchased in a plastic pot, deal with girdling roots in one of two ways. The first option is to gently wash the root ball to remove all soil. Once roots are exposed, spread them out and prune away any that circle the trunk. Keep the roots moist during the process and until they are planted. The second option is to shear off one inch of the entire outer root ball with a sharp hand saw. This has been shown to be more effective than making several cuts or slices down the sides of the root ball.

Eliminate Stem Girdling Roots Before Plantings, Nebraska Extension 

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8. May is Wildfire Prevention Month

May is wildfire prevention month. Wildfires have been headline news not only in Nebraska but across the country. It’s comfortable to think that a devastating wildfire can’t happen in your area, but it’s better to be aware of the possibility and be prepared. Learn the aspects of Fire Smart Landscaping including creating a defensible space, planning ahead for a fire event, storing firewood at least 20 feet away from a house, reducing the density of landscape plantings and management of the surrounding landscapes to decrease potential fire damage. 

For more information on mitigating wildfire hazards, visit the Weather-Ready Landscapes Page

Also, view this guide from the Nebraska Forest Service: Rural Homes and Wildfire

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9. Ground Ivy

Ground ivy, Glechoma hederacea) is a low growing perennial weed that is starting to bloom. Found in lawns, gardens, and flower beds this perennial can quickly take over if not managed. In the laws try to mow at 4" and encourage a thick stand of turf. In the flower/garden beds you will need to manage by hand by gently pulling up plant. Chemical management is best done in the fall.

Ground ivy and henbit are often confused. They look similar but with a few small differences. Henbit upper leaves clasp the stem where as ground ivy leaves are attached by petioles. Henbit will have a pink-purple flower where as ground ivy flowers are blue-purple. Henbit is an annual and ground ivy is a perennial. 

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10. Commercial/Non-commercial pesticide applicators

If you have a pesticide applicators license which expired in April 2026 or you need to get a new license, testing options are listed below.

Testing-only Options

• Closed-book exams are given by the Nebraska Department of Agriculture (NDA). Preregistration is not required an there is no cost. Visit the link below for a list of available test-only dates, times and locations - https://pested.unl.edu/.
• NDA computer-based testing is provided through the Pearson-Vue company. Click here for a list of testing sites, categories available, dates, and registration information. Cost $55 per exam. (For applicators with multiple categories on their license, each category is charged the full testing fee.)

Commercial/noncommercial applicators are professionals who apply restricted-use pesticides for hire or compensation. Anyone who applies pesticides to the property of another person, either restricted- or general-use products, for control of pests in lawns, landscapes, buildings or homes must also have a commercial pesticide applicators license. Public employees (those employed by a town, county, state) applying mosquito control pesticides whether restricted- or general-use, must also hold a commercial or noncommercial certification.

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11. Digital Diagnostic Network - Need help with diagnostics?

Do you or your clients have questions you need help answering? Maybe you are a lawn care person and they're asking about trees, shrubs, or flowers? While you can refer them to their local Extension office, another option is Digital Diagnostic Network. Homeowners, lawn care professionals, pest control operators and others are invited to submit questions and photos through this website or with the assistance from an Extension professional at any Nebraska Extension office. All offices are equipped with high-resolution digital image capturing technology. Whether the question is about a lawn weed, insects on a plant, diseases in a shrub border or other, an expert panel of Extension professionals will review and respond to the question. To get started, create an account so the question can be reviewed and responded to via email. For more information and to create an account, go to Digital Diagnostic Network.

Bugging Out With Your Camera Phone - Tips on how to get a good picture.

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Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by Nebraska Extension is implied. Use of commercial and trade names does not imply approval or constitute endorsement by Nebraskas Extension. Nor does it imply discrimination against other similar products.