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Hort Update for January 3, 2022

Hort Update for January 3, 2022, Nebraska Extension,
Winter is a good time to assess trees for potential hazards.

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Serious ConcernsMajor Symptom
1. Assessing trees for hazards Identify common defects; develop a pruning plan for late winter or early spring
2. January growing degree days (GGD) Lincoln Airport 1/1/22 - 0 GGD,  Understanding Growing Degree Days
Timely Topics
3. Turf winter desiccation & death of fall laid sod Replace or repair in spring
4. Optimum time to prune has changed International Society of Arboriculture (ISA) pruning guidelines updated
5. Effects of freezing or wetness on stored pesticides and fertilizers Improper storage can reduce effectiveness

1. Assessing trees for hazardsIdentify common defects; develop a pruning plan for late winter or early spring

Tall shade trees are needed to create climate-resilient landscapes and communities, not to mention nicer places to live and provide energy conservation. We also need trees to be structurally sound, so they are weather ready.

Winter is a good time to assess shade trees for potential hazards. During winter, branch structure and areas of damage are easier to see, since leaves are not hiding them. Observe shade trees now for faults and pruning needs but wait until late winter or spring to prune.

Common Defects
To assist professionals and their clients in inspecting, Nebraska Extension has a publication titled Tree Hazard Awareness. It provides photos to assist in identification of common potential issues, including co-dominant leaders, cracks, decay, fungal conks, girdling roots and trunk lean.

Once these faults occur, it can be difficult to correct them. The best way to create a structurally sound tree and avoid other issues is with correct pruning during the first 3 to 15 years of a trees life.  This is a topic that will be covered in upcoming ProHort Updates to be held in February and March.

Trees are a long term investment providing numerous benefits. It's a smart investment for homeowners to hire a professional arborist to check their trees every five years for pruning needs. Tree owners often wait too long, until trees are too mature and it is difficult to correct structural issues, which may turn into hazards.

Co-dominant leaders, crossing or rubbing branches, and branches with weak attachments are all common tree faults which can easily be corrected with pruning in young trees. It's healthier for the tree to remove branches when they are small; smaller wounds are created and the risk of wound decay decreases.

Don't Use Wound Dressings
While it is best to hold off on pruning trees until late winter, now is a good time to remind people not to use tree wound dressings, pruning paint, or any products available for sale that says it will promote healing of tree wounds. When a tree branch is pruned, human instinct is to put a band aid on the wound but this is one of the worst things we can do. Tree wounds do not heal; instead they seal off wounded or damaged areas.  and so no wound dressing product has been showen to promote healing.

When a tree is wounded, such as with pruning, it sends defense chemicals to the wound to seal it off. Then, during the growing season, the tree develops wound wood to close the wound. Research has shown any type of tree wound dressing interferes with a trees natural defense mechanisms and with the sealing process. Wound dressings also trap moisture to promote decay and prevent wound wood from forming.


3. Turf winter desiccation and death of fall laid sodRepair or replace in spring

Warm 2021 fall conditions were conducive to late sod installations, even into November. Watering new sod is critical and should be done daily for at least the first few weeks. However, fall conditions were also dry and if homeowners did not water enough portions of their sod may not have survived. Dead sod shrinks leaving open spaces or cracks between the pieces and will be a uniform brown, instead of the normal green/brown of dormant Kentucky bluegrass or tall fescue. Pieces can be lifted easily since roots did not develop sufficiently, with the shortened day length and growth potential. 

Dead sod pieces should be removed in spring and replaced. If only small sections of sod are dead, the cracks between pieces should be filled with soil and the entire area overseeded. Be sure to match species and cultivars if possible, so the repair is indistiguishable from the original sod. 

Establishing Lawns from Sod, Nebraska Extension 

In the absence of rain or snow cover, even established turf may experience winter desiccation injury, particularly turf with a high percentage of perennial ryegrass. The risk is greatest for golf and sports turf growing on sand soils. Stands with lots of thatch are more likely to have issues with winter desiccation (i.e. tees and fairways). Lawns of predominately Kentucky bluegrass, fescue, or buffalograss are much more tolerant of winter desiccation stress.

On lawns, the risk of desiccation is usually greatest on exposed or elevated areas where water surface runoff is greatest, and on poorly rooted turf that cannot take up water that is deeper in the soil profile. An example would be turf growing in heavy clay soils that were compacted and not prepared properly before seeding/sodding.

If needed on exposed sites, water only when the soil is not frozen and air temperatures are above 40º F. Apply water at mid-day so it has time to percolate into the soil before potential freezing overnight. Water just enough to moisten the crown of the plants. Apply water slowly enough that it soaks in and does not run off or pool and freeze around plant stems or crowns overnight.  


4. Optimum time to prune trees has changesInternational Society of Arboriculture (ISA) Pruning Guidelines Updated

It was previously recommended the best time to prune most shade trees was during winter dormancy.  New research shows the optimum time to prune living branches is late spring and early summer because pruning at this time promotes the quickest sealing of pruning wounds, known as CODIT or Compartmentalization of Decay in Trees. Late spring and early summer is when tree cells are most active during the growing season, hence sealing occurs the quickest. 

Winter, or anytime during the dormant season, has commonly been the recommended time to prune shade trees. We know trees can be pruned most anytime without killing them, but there are ideal times to prune and times when pruning is best avoided.

We may not have a choice on timing, such as after a wind or ice storm and broken branches need to be removed for safety; but when we have a choice, aim for the ideal time; especially if you are a do-it-yourselfer pruning smaller branches off a smaller tree. Pruning of large branches in large trees should be left to professionals.

ANSI A300 Pruning Standard 


5. Effects of freezing or wetness on stored pesticidesImproper storage can reduce effectiveness

Store pesticides correctly and securely.  Storage information can be found on pesticide labels.  Read and follow it for safety and to help keep pesticides from degrading so they may no longer be as effective.

In general, pesticides need to be stored in a secure, well ventilated location that can be locked. The location should be away from children, pets and food items as well as anything that might be contaminated in case of a leak or accidental spill. 

Do not store pesticides near heat, sparks, or open flames; and check that containers are tightly closed. Always store pesticides in their original containers.  A mistake made is pouring a pesticide into a container other than the original. This is against pesticide label law and has led to accidental poisonings. 

A common question about winter storage is if a pesticide is still effective after it freezes.  Most pesticides are safely stored between 40 and 100 degrees Fahrenheit, but it is best to check the label for storage temperature requirements and any warnings against freezing.  If a liquid pesticide does freeze, it might be less effective in controlling pests. 

Pesticides contain active and inactive ingredients. The active ingredient is what kills the pest. Inactive ingredients include solvents, carriers, or emulsifiers that make the pesticide more efficient. Due to some inactive ingredients, the freezing point of some liquid pesticides could be lower than 32 degree F. Read the label for temperature storage requirements and what to do if a pesticide does freeze.          

Pesticides formulated as wettable powders or granules are not affected by low temperatures. However, moisture can cause caking that may reduce effectiveness so follow label directions for correct storage recommendations. If you have products formulated in water-soluble packets, these should not be frozen as they tend to become brittle and then break open.

Safe Transport, Storage, and Disposal of Pesticides, Nebraska Extension 


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 Nebraska Extension. Nor does it imply discrimination against other similar products.