Hort Update for December 22, 2016

Lawns
Major Symptom:
1. Avoid traffic on frozen turf Cosmetic damage can occur
2. Turn irrigation systems off If not done already
3. Vary snow pile locations Helps avoid excess deicing salts in one location
   
Trees & Shrubs  
4. Anti-desiccant applications If needed, make applications when temps are above 40°F
5. Water when soil not frozen May be needed if temperatures warm and moisture lacking
6. Sunscald Particularly common on young thin-barked trees
7. Vole control Use barriers and exclusion
   
Landscape Ornamentals  
8. Don't prune shrub roses Shrub rose pruning in December and January not recommended
9. Don't prune hydrangeas Hydrangea pruning in December and January not recommended
10. Frost heaving Monitor fall planted perennials for signs of frost heaving
   
Fruits & Vegetables  
11. Strawberry winter protection Imperative for best overwintering success
12. Reccomendations for purchasing fruit trees Fruit Tree Cultivars for Nebraska
   
Miscellaneous  
13. Introducing John Porter New Nebraska Extension Urban Agriculture Educator

1. Avoid traffic on frozen turf -  Foot or vehicle traffic on frosted or frozen turf can cause cosmetic damage; resulting in foot prints, pathways or tire tracks across the turf that may not recover until late spring.  Unlike actively growing grass, dormant grass does not have the capability to recover until growth resumes.  Minimize traffic as much as possible and use varied paths if you must walk on turf. 

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2. Turn off irrigation systems to avoid damage. Refer to the Preparing Your Sprinkler System for Winter, Colorado State University, for tips on preparing home sprinkler systems for winter.  

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3. Vary snow placement when shoveling - Large piles of slow to melt snow can lead to issues with snow mold disease or turfgrass suffocation if other conditions are also conducive.  Where de-icing products are used, piling snow with deicer in it may lead to soil issues. Spreading piles around disperses snow weight and deicing quantity to help reduces potential issues.

Winter Deicing Agents for the Homeowner, Nebraska Extension

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4. Antidessicant applications can be made when temps are above 40F.  Also known as anti-transpirants, these products help plants endure stressful periods by reducing transpirational water loss from foliage. The most common types of anti-desiccants 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 carefully.

As a rule, apply the product once every six weeks beginning after plants have completely hardened off, usually in late November.  Continue applications 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.  One common anti-transpirant available through nurseries and gardens centers is called Wilt-Pruf, but other products are available

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5. Winter watering of trees and shrubs will be beneficial if warm winter temperatures and a lack of precipitation occur. The priority for watering is young plants first - those planted in the last year and especially those planted this past fall, and then evergreens, especially 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. Irrigation should take place early enough in the day for moisture to soak into the soil to avoid ice forming over or around plants overnight. Water just enough to moisten the soil six to eight inches deep. One or two irrigations during winter should suffice. If conditions become warm and dry in winter and into spring, it will be critical to begin irrigation as soon as soils thaw this spring.

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6. Sun scald commonly occurs on young, tender barked trees, such as Maples, during winter. It may be due to uneven heating of the trunk; however, there appears to be a correlation to root damage during transplanting. Proper planting and post planting care may be more important to protecting trees from sunscald than tree wrap. If used incorrectly, or left on too long, tree wraps can cause more harm than good. If used, tree wraps should be attached in late November/early December at the soil line and the tree wrapped upward with the wrap overlapping up to the first set of branches; then removed in spring. Leaving wraps on too long may girdle or compress the trunk, reduce photosynthesis, and increase insect (borer) damage. Avoid the use of paint as these may cause chemical damage to the trunk.

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7. Wildlife barriers, such as hardware cloth around tree trunks or chicken wire cages around shrubs, are the best means of protecting plants from wildlife feeding during winter. To be successful, the key is to know what the average snow depth is and to be sure the wildlife barrier is height than expected or potential snow levels. If the barrier is buried by snow, wildlife can still access the trunk and cause girdling damage.

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8. Don't prune shrub or tea roses until March. While some of the hardier roses can be pruned in March, most hybrid tea rose growers should wait until just before new growth begins to prune roses. This can help reduce the risk of additional cold temperature injury that may occur as a result of early pruning. On all roses, first prune out any winter killed canes by making an angled cut just above the nearest outward facing healthy bud.

Shrub roses require very little pruning. In March prune out any stems that have winter killed. Also thin canes smaller than pencil diameter and remove crossing canes or those too densely arranged in the crown.

Shrub Rose Pruning, Nebraska Extension
Roses: Care After Planting, University of Missouri Extension

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9. Don't prune hydrangeas - When, what and how much to prune is determined by the type of hydrangea being grown and on what age wood each hydrangea-type produces flowers. Some can be pruned while dormant and other hydrangea-types should be pruned after blooming. Others are pruned a little while dormant and again after blooming. But dormant season pruning in December and January is not recommended. Waiting until late March just before new growth begins is a preferred practice. See the video link below for pruning information for Hydrangeas.

Pruning Hydrangeas with Kim Todd, Nebraska Extension Backyard Farmer

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10. Frost heaving occurs in winter when temperature swings cause garden soil to alternately freeze and thaw resulting in damage to a plant's dormant crown and root system. Plants at greatest risk are fall planted perennials that may not have had enough growing time to develop a good root system to hold them in place. Once the crown and root system are exposed to winter air, desiccation can occur resulting in root or plant death. Frost heaving is reduced in plantings where an application of winter mulch is made, because of its ability to reduce swings in soil temperatures keeping them cold. If mulch has not yet been applied to fall planted perennials, it is not too late to apply it now. Spread a loose layer of mulch approximately two inches deep. The mulch should remain in place until late March to early April next year.

Examine fall planted perennials periodically in winter looking for signs of cracks around the plant's root system or evidence of the plant being pushed up out of the ground. If cracks exist fill them with topsoil and reapply mulch to maintain a two-inch layer. If winter conditions are dry, water fall planted perennials during warm periods when the soil is not frozen. Watering will not cause new growth to start, but is essential to prevent root death from dry conditions.

Suitable mulches include wood chips, pine straw, evergreen boughs, straw, clean hay or any loose mulch that will not compact heavily.

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11. Strawberry winter protection – Strawberry plantings must be mulched for winter to prevent or reduce winter damage to the strawberry crown and flower buds. Most unprotected strawberry cultivars are injured at 15°F. Do not mulch too early. Wait until late November or early December; then apply loose mulch to a depth of four inches in late November/early December after the soil has frozen to a depth of 1/2 inch, or the temperature has dropped to the 20s.

If mulch is applied too early it can delay hardening off, making plants more susceptible to winter injury, and increasing crown rot. Suitable mulches include wood chips, pine straw, newspapers, coarse sawdust, straw, clean hay or any loose mulch that will not compact heavily. The mulch should remain on the strawberry plants until new growth begins, about mid-April.

Fall and Winter Care of Strawberries, Nebraska Extension

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12. Fruit Tree Cultivars for Nebraska is now available through Nebraska Extension at extensionpubs.unl.edu. Proper fruit cultivar (variety) selection is important for successful and satisfying results from the home gardener’s efforts. Selection should be based on family preferences, available space, and intended use of the fruits. If properly chosen, harvest can be spread over several weeks if cultivars with different periods of maturity are planted. Disease resistance, harvest dates, winter hardiness and plant size are also important considerations.

Horticulture industry professionals should assist homeowners to select fruit cultivars best-adapted for cultivation in the part of the state in which they live. The cultivars must have adequate hardiness to survive the winter; heat and drought tolerance to thrive in the summer; and the ability to escape or survive spring frosts.

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Nebraska Extension HortUpdate for December 22, 2016. http://hortupdate.unl.edu/update12222016#Thirteen13. Introducing John Porter, who will join Nebraska Extension January 17, 2017 as the new Urban Agriculture Educator. John will be officed at the Douglas/Sarpy office. He is formerly a West Virginia University (WVU) Extension Agent for Agriculture and Natural Resources and an assistant professor with the WVU Extension Service. His expertise in urban agriculture and he has a passion for locally grown food. John has Bachelor of Science degree in botany/biology from Marshall University and an Master of Science in Horticultural Sciences from WVU.

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Seasonal information for Nebraska's green industry professionals.

Continuing Issues

Lawns

Trees & Shrubs

  • Emerald Ash Borer Resources - EAB was confirmed in Omaha, NE 6/8/16 and Greenwood, NE 6/17/16. It is recommended homeowners wait to begin treating their ash trees until the insect is confirmed within 15 miles of their location. 
  • Basic EAB Information

Fruits & Vegetables

Local Conditions

Image of water

Dry conditions are a frequent condition in Nebraska.  Stay informed on current conditions, and public water utilities restricting water use. Visit UNL Drought Resources.

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