ProHort Update for December 2024

1. Dormant turf seeding

Traditionally, lawns are seeded in spring (April-May) or fall (August-September), but there is another option - dormant seeding. With this method, the area is prepared in fall but the seed is not distributed until after the growing season has ended. Seed remains in place during winter, but does not begin to grow until soil temperatures are warm enough next spring for germination. If turf you manage still needs some work, and establishment in spring, consider dormant seeding.

Dormant seeding has several benefits. 

• First, soil preparation can be done longer in fall - past the time for successful fall seeding. Dry fall conditions are an advantage to complete site preparation. 
• There’s no rush to get the work done in a short window of time in spring between frozen soil and wet soil. 
• Dormant seeded turf grows well and fills in during cool spring weather, preventing much of the potential invasion by weeds. 
• Finally, plants have more time to develop vigor and a good root system before hot summer conditions arrive, making them more able to tolerate summer stresses.

Soil Preparation Creates a Good Seedbed
The actual process of seedbed preparation is the same as at other times of the year, but dormant seeding is most effective when soil preparation - usually core aeration - is done in fall. Simply broadcasting seed and allowing it to work into the soil naturally through frost-heaving won't provide great success. Soil preparation to improve seed-soil contact is highly recommended and will be worth the effort.

The best technique for preparing larger areas is aerating. Aeration opens up the soil and provides a good surface for seed germination. Seeds that fall into the aeration holes will germinate and grow well; there is no need to topdress or fill in the holes before seeding. Prepare small areas by hand raking to remove excess dead top growth and loosen the soil surface.

Power raking can also be used to prepare the site, but is more damaging to existing turf and is not recommended when the existing turf is dormant and no longer growing. When plants are not growing, they have limited ability to repair power raking damage, so could be susceptible to winter injury. The only benefit of power raking over aeration is to reduce excess thatch. Up to ½” thatch is beneficial to lawns, acting as a mulch for turfgrass roots and cushioning the surface for more comfortable walking. However, if more than 1/2" thatch is present and power raking is used, go over the turf lightly only deep enough to penetrate the top ¼” of soil.

Seeding
Once seedbed preparation is done, dormant seeding should ideally take place from mid-December through mid-February. Soil temperatures must be 40° degrees F or below to ensure seeds will not germinate. Since the seed needs to have good soil contact, don’t apply seed over snow. Dormant seeding should be done no later than March 15th.

The seeding rate for new, bare lawn areas is as follows: Kentucky bluegrass 2-3 lbs. per 1,000 sq.ft. and tall fescue 6-8 lbs. per 1,000 sq.ft.

The amount of seed applied when overseeding into a thin lawn is usually half the amount used for a new seeding. Kentucky bluegrass should be applied at 1-2 lbs. per 1,000 sq.ft. and tall fescue at 3-4 lbs. of seed per 1,000 sq.ft. When working with small amounts of seed, mix sawdust, dry sand or any other suitable material with the seed to aid in obtaining uniform coverage.

Fertilization and Weed Control
Applying a pre-emergent herbicide for weed control can be done in spring, but use only products labeled for new seedings including mesotrione (Tenacity) or siduron (Tupersan). These herbicides will provide good control of annual grassy weeds like crabgrass and foxtail, yet still allow the grass seed to germinate and grow.

Do not apply the pre-emergent herbicide when the seed is broadcast. Pre-emergent herbicide applied too early is a waste because it will begin to degrade before weed control is needed and won't provide effective control when weed seeds do begin to germinate next year.

Instead, wait to apply pre-emergent between mid-April and the first week of May. Several days of soil temperatures 55° degrees F or above are required for crabgrass and foxtail seeds to germinate. Be sure the pre-emergent herbicide is in place before that time for good weed control. Monitor your local soil temperature at Nebraska Extension’s ProHort Update.

For new seedings, use the lower recommended rate and repeat the application one month later.

Pre-emergent herbicide is usually combined with a starter fertilizer for new seedings. A combination application made between mid-April and the first week of May is a good way to provide fertility and control weeds at the same time.

Watering
Don’t rely solely on spring rain for seed germination. Irrigate the seeded area several times a day during the first two weeks, depending on rainfall and temperatures. Keep the top 1/2 to 1 inch of soil moist as the seedlings germinate. Taper off irrigation as the seedlings develop. As they approach mowing height, reduce the number of irrigations to 2 to 3 per week, but water more deeply with each application to encourage deep root development.

Begin mowing as soon as possible. Mowing encourages tiller (secondary stem) development, and helps new plantings thicken up quicker. It also keeps weeds under control while the new seedlings become established. Just be sure your mower blade is good and sharp!

Watch Winter Weather Conditions
One risk involved with dormant seeding is warm winter and early spring temperatures. If warm conditions cause seed to germinate and are followed by a cold period, seedlings may be killed. Continuous snow cover provides the best protection for seeds. Monitor seeded areas in mid-spring for the need to do additional overseeding, but give the seeds plenty of time to germinate.

Establishing Turf from Seed, University of Nebraska Turfgrass Science Program

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3. Labeling Plants Pollinator-Friendly Influences Consumers

The Journal of Extension research in brief article: ‘Buzzworthy Messaging: Assessing Residents’ Perceptions of Labels to Better Promote Pollinator Gardening’ looks at plant labeling influence on consumers. 

Abstract: Consumers appear more likely to purchase plants with labeling indicating pollinator-friendly production or high pollinator resource value. No standardized label for pollinator-supporting plants or landscape practices exists in the United States, which has proliferated the variety of labels used by the industry. This mixed-methods study aims to provide insight into residents’ preferred pollinator-related labelling for plants and landscape practices in order to help Extension professionals and green industry stakeholders improve outreach, marketing, and communications efforts. Findings suggest a butterfly-friendly label would be most effective for marketing while residents would accept and favorably perceive labels emphasizing either pollinator-friendly or bee-friendly attributes.

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4. Select Shade Trees with Climate Change in Mind

After a season of high storm damage, homeowners may comment they want to replace a damaged tree with a smaller tree to reduce the risk of damage. The benefits of large shade trees are too important in our community forests; especially with weather extremes increasing. 

With a changing climate and the long life of trees, it becomes more challenging to know which trees to recommend. The U.S. Department of Agriculture Forest Service has developed a Climate Change Tree Atlas with regional summary tree tables developed through modeling. The tables are a tool to support decision-making in natural resource planning and management. They provide broader insights into how groups of tree species will fare across a variety of regions and scales. 

The USDA Forest Service’s Climate Change Tree Atlas explores adaptation potential for 125 tree species. Trees were given an “adaptability rating” to indicate how likely they would adjust to climate conditions in 2100 under low and high greenhouse gas emissions scenarios. For example, for Omaha in the urban area category, bur, red and shumard oak, hackberry, honeylocust, eastern hophornbeam, and bitternut hickory were tree species expected to be more adaptable.

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5. Avoid walking on frozen turf

If ice crystals (frost) have formed and foot or vehicle traffic occurs, the physical abrasion can damage turfgrass. Winter traffic can cause cosmetic damage, physical abrasion, and/or soil damage depending on the situation. Too much traffic on turfgrass at a time when it cannot recover also leads to winter injury. Winter golf or over-using soccer fields during winter are examples.

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6. Using de-icers correctly

De-icing agents are sometimes needed for safety but can be harmful to plants. Common deicing compounds are listed below in order of potential plant damage, with the most damaging first. These may be used alone or blended to improve performance or reduce damage to concrete or landscapes.

• Sodium chloride is the least expensive product and commonly used on roadways. It has a high burn potential for landscape plants.
• Urea can harm landscape plants and cause runoff pollution in ponds and waterways.
• Potassium chloride, also known as muriate of potash, is less damaging than sodium chloride.
• Calcium chloride is the most effective deicing product at low temperatures, working down to ­‐25°F. It will not damage vegetation if used as directed.
• Magnesium chloride is sprayed on roadways before a snowstorm to prevent ice bonds from forming, making ice and snow removal easier. It causes very little damage to concrete or metal. It's also gentle on landscape plants and pet safe if used as directed.
• Acetates can be found in three forms - ­calcium magnesium acetate (CMA), sodium acetate and potassium acetate. CMA is a salt-­‐free product and is the safest product for use around pets and landscape plants. CMA is made from dolomitic limestone and acetic acid (the principal component of vinegar). Studies have shown the material has little impact on plants. It also has a very low level of damage to concrete or metal.

Also keep on hand products that improve your footing on slick surfaces, like sand, sawdust, or cat litter. They can be used instead of traditional deicing products or blended with them to improve traction and limit deicer use. Be sure to use the recommended rates for limited damage to plants nearby. 

Winter Deicing Agents for the Homeowner, NebGuide G1121

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7. Snow removal tips

When doing snow removal, spread the snow out as much as possible instead of piling it in one place. Piled snow may lead to branch breakage in shrubs, matted turfgrass, and buildup of salts in soil where de-icing products are used. Turf areas with piles of snow are prone to snow mold and the longer snow covers the turf surface, the more time for vole damage to occur.

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8. Winter watering and anti-transpirants

Winter watering is always important, especially in light of the long-term drought we have faced. Recent rains have helped alleviate the problem, however, if an absence of snow cover and warm, sunny or windy weather conditions are common this winter, watering can be beneficial. The priority for watering is young plants first - those planted in the last year and especially those planted this past fall; then evergreens, particularly those growing in exposed locations and near the south sides of buildings.

When watering, the soil should not be frozen and air temperatures need to be above 40 degrees F. Irrigation should take place early enough in the day for moisture to soak into soil to avoid ice forming over or around plants overnight. Water enough to moisten the soil 6-8 inches deep. One or two irrigations during winter should suffice. If conditions remain warm and dry through winter and into spring, it will be critical to begin irrigation as soon as soils thaw this spring. 

Antidesiccants, also known as anti-transpirants, help plants endure stressful periods by reducing transpirational water loss from foliage. The most common types of antidesiccants are an emulsion of wax, latex, or plastic that forms a thin film on foliage to minimize water loss from plants. We recommend their use on evergreen conifers or broadleaf evergreens in winter, particularly on plants with a history of winter desiccation injury or plants susceptible to winter drying like arborvitae, holly and mahonia. Select the right product for the plant species as there are toxicity issues. Read and follow label directions.

Apply the product once every six weeks, beginning after plants have completely hardened off in late November. Continue through mid to late February. Avoid covering plants so heavily they become sticky with needles glued together. Have warm, soapy water nearby and clean out the sprayer immediately or equipment may be ruined by the product.  

Irrigation through Fall and Winter, Plants and Pests Blog from Nicole Stoner

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9. Mulch

Trees and landscape plants are often mulched. While we know mulch conserves soil moisture and controls weeds during summer, a benefit we may not think about is how mulch protects soil from temperature extremes and how this benefits plants. Mulch keeps soil cooler in summer and minimizes soil temperatures fluctuations in winter. This benefits plants because temperature extremes can kill very fine roots which are responsible for most water and nutrient absorption.

While soil temperature extremes rarely kill established plants, they can cause a chronic stress as plants expend energy to generate new fine roots. This may allow opportunistic pests, like root rots, to infect.

Moderating soil temperature is especially important near the soil surface, where fine roots can be killed by hot soils in summer and by desiccation and frost heaving during winter. The correct use of organic landscape mulch benefits plants year-round. Coarse mulches, like wood chips, tree leaves or recycled greenery, make great mulches.  

Apply mulch in an even layer, 2 to 4 inches deep, around woody plants and 1 to 2 inches thick around annual and perennial flowers. Mulch should be kept an inch or two away from plant stems, even tree trunks. Watering organic mulches after installation will increase their ability to hold together and minimize movement during heavy rains or gusty winds.

Impact of Mulches on Landscape Plants and the Environment: A Review, Journal of Environmental Horticulture

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10. Commercial/Non-commercial pesticide applicators

If you have a pesticide applicators license which expired in April 2025 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.)

2025 Commercial/non-commercial training is held from January through April. Training schedules will be available soon at https://pested.unl.edu/. Help your employees be successful at getting a license by purchasing study materials. 

Extension and industry-sponsored events also offer opportunities to renew a license. Recertification only.

• Jan. 8-28 | Nebraska Extension Crop Production Clinics - 00 general standards, 01 ag plant, demonstration/research
• Jan. 7-9 | Nebraska Turf Conference - 00 general standards, 04 turf & ornamental 
• Feb. 19-21 | Nebraska State Pest Control Association Conference
• Feb. 24-26 | Nebraska Aviation Trades Association Convention

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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 constitue endorsement by Nebraskas Extension. Nor does it imply discrimination against other similar products.