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Hort Update for December 2017

Nebraska Extension Hort Update for December 2017,
Covering plants especially sensitive to salt with burlap or other materials can reduce damage caused by salt spray from roads. Image by Janna Beckeman, Purdue Extension
LawnsMajor Symptom:
1. Winter watering of turf Is it needed and when to water
2. Establishing turf from sod Specific care needed for winter laid sod
3. Salt damage mitigation Be alert for areas with high potential for salt intrusion
4. Alternative products for managing ice Use calcium magnesium, sand or kitty litter to provide better traction
Trees & ShrubsMajor Symptom:
5. Winter watering of trees & shrubs Beneficial when soil is not frozen
6. Salt damage in trees & shrubs How it occurs and how to diagnose
Landscape OrnamentalsMajor Symptom:
7. Early bud swell in trees, growth in perennials and bulbs Unseasonal growth seen in trees, shrubs, perennials & bulbs following warm early winter conditions
8. Planting bulbs now? Expect reduced survival, extra winter care needed
Fruits & VegetablesMajor Symptom:
9. Winter greenhouse insect control Success relies on early detection and effective control
10. Soil labs & testing Provides good basic soil information to direct soil improvement
11. Understanding a soil test Key elements of a soil test report and what they mean
12. Soil preparation for spring crops Can still be done before soil freezes
MiscellaneousMajor Symptom:
13. Recycling Christmas trees Shelter for birds, feeding station, mulch, fish habitat
14. Controlling indoor houseplant insects Success relies on early detection and effective control

1. Winter watering of turfis it needed and when to water

Winter watering of turf may be beneficial in the absence of rain or snow cover to help prevent dessication injury. 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 40 degrees Fahrenheit. 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.

Winterkill of Turfgrass, PennState Extension


2. Establishing turf from sodSpecific care needed for winter laid sod

Turf areas can be sodded almost any time soils are not frozen. Sodding in early spring or early fall is preferred since irrigation requirements are less than when sodding in summer. Sodding in winter can be done as long as winter irrigation is available to minimize winter desiccation on exposed sites. For winter sodding, soil preparation is just as important as for other times of the year and the soil must be moist when sod is laid. Watering after installation is a priority, even in winter. The goal in winter is to keep the crowns moist to prevent winter dessication and sod death. 

Establishing Lawns From SodNebraska Extension Turf iNfo


3. Salt damage mitigationBe alert for areas with high potential for salt intrusion

Salt damage to turf growing near pavement where deicing agents are used does occur. High salt levels change the structure of soil, causing it to become compacted and restricting the availability of nutrients, water and oxygen to plants.  In summer, high salt levels decrease a plant's ability to absorb sufficient water, even when water is available. Symptoms of salt damage include stunting, leaf burn, root damage, and plant death. 

To help limit issues, use the smallest amount of product needed to manage ice.  Select products known to cause less soil/plant damage.  Avoid piling snow containing salt on turfgrass.  Consider mixing cat litter or sawdust into deicing products to reduce the amount used.  In runoff areas affected by high salt levels, flushing the soil with 2" of water over a 2-3 hour period in early spring may help leach salt from soil. Repeat this procedure 3 days later. If the soil is not well drained in the area, leaching will not work well. In cases with repeated and heavy deicing salt use, removing the top four to six inches of soil may be needed. To protect a site from a spray of salty slush during snow removal, a barrier made with burlap cloth may also be set up.


4. Alternative products for managing iceUse calcium magnesium, sand or kitty litter to provide better traction

One way to protect landscape plants is to use products with lower potential for damage such as a salt-free melting agent called calcium magnesium acetate (CMA). CMA is made from dolomitic limestone and acetic acid (the principal component of vinegar). Studies have shown the material has little impact on plants. Also consider products that improve your footing on slick surfaces, like sand, sawdust, or cat litter. They can be used instead traditional deicing products, or blended with them to improve traction and limit deicer use.

Winter De-icing Agents for Homeowners, Nebraska Extension


5. Winter watering of trees and shrubsbeneficial when soil is not frozen

Winter watering of trees and shrubs will be beneficial this year if warm winter temperatures and a lack of precipitation continue. The priority for watering is young plants first - those planted in the last year and especially those planted this past fall, and 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 Fahrenheit. 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 just enough to moisten the soil six to eight 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. 


6. Salt damage in trees and shrubshow it occurs and how to diagnose

Salt damage of trees and shrubs occurs in three ways: 1) Salt sprayed directly on the plant makes the plant lose cold hardiness and become susceptible to freezing; 2) Salt accumulation in the soil absorbs water, making it unavailable to plants; and 3) Chloride ions are absorbed by the roots, transported to the leaves, and accumulate there to toxic levels - it is these toxic levels that cause the characteristic marginal leaf scorch. Evergreens are particularly sensitive to salt damage. 

To determine if salt is playing a role in damaging your plants, be sure to note which side of the plant has more severe symptoms. In salt-damaged plants, the symptoms will be more severe on sides facing the road or sidewalk. In evergreens, damage usually appears in late winter as needle browning that starts at the tips. Keep in mind that snow covered branches will be less affected than those exposed to salt spray, and that as you move away from the spray zone, the symptoms should abate. It is more difficult to diagnose spray damage on deciduous plants. Usually, leaf buds facing the road are killed or are very slow to break dormancy and bud and leaf out in spring. Flower buds facing the road often fail, but the unaffected side of the tree or shrub flowers normally. Repeated salt damage over several winters may produce a witch’s broom effect, which is a tufted and stunted appearance of the plants on the side facing the road.

The easiest way to prevent salt damage is to avoid it. Whenever possible, use coarse sand instead of salt to provide traction and make sidewalks and driveways less slick. If you must use salt, use it judiciously, and erect barriers with plastic fencing, burlap, or snow fencing to protect sensitive plants and minimize their contact with salt. When possible, consider non-sodium de-icing agents such as calcium chloride or calcium magnesium acetate (CMA), a salt-free melting agent made from limestone and acetic acid. In years when large amounts of salt are used, minimize plant damage by irrigating soils to leach out the sodium and chloride prior to spring growth. Since most salts are water-soluble, thorough and repeated applications of water can effectively leach salts out of the root zones. 

Salt Damage in Landscape Plants, Purdue Extension


7. Early bud swell in trees, growth in perennials & bulbsUnseasonal growth seen in trees, shrubs, perennials & bulbs following warm early winter conditions

Entering dormancy for landscape trees, shrubs and ornamentals is triggered in fall by changing day length and temperatures. Woody plants have a chilling requirement (measured in hours below a certain temperature) that delays any new growth until after a typical winter period is past, delaying new growth until spring conditions are favorable. This chilling period varies with plant species, however plants native to southern climates usually have a shorter chilling requirement than plants native to northern locations.

Warm early winter conditions have resulted in bud swell and even blooming in some plants with shortern chilling requirements, such as forsythia. Flower buds "used up" now, will decrease the plant's flower display next spring. Vegetative buds that have swollen or lost winter hardiness are more prone now to sudden changes in temperature. Gradual temperature drops may allow buds to reenter dormancy. However, there isn't much that can be done at this point to help. 

Perennial plants or bulbs are also showing growth in some locations across Nebraska. Fortunately the flower bud for bulbs is deep inside the bulb itself. A sudden temperature drop may damage foliage, but the flower is unlikely to be affected. Perennials sending out new growth may be burned back by cold winter temperatures to come, but little long term damage should be seen. If possible, bury perennials or bulbs that are starting to grow with wood chip mulch to keep them colder. This will help reduce any further growth and protect plant crowns.  


8. Plant bulbs now?Expect reduced survival, extra winter care needed 

If customers still have bulbs they have not planted and their soil is not frozen, bulb survival will be better if they are planted. Following planting, bulbs should be well watered and mulched with 3-4 inches of wood chips. Since there is time for little to no root establishment gardeners will need to provide periodic watering if winter conditions are dry to prevent bulb desiccation. 100% survival is unlikely, but likely will be better than for bulbs stored in the home until next year. 


9. Winter greenhouse insect controlSuccess relies on early detection and effective controls

Insects can be a serious problem during winter greenhouse production. White flies, fungus gnats and mites are frequent problems. Successful control relies on early detection and identification, monitoring and effective control methods. 

Greenhouse Insect Management, University of Kentucky


10. Soil labs & testingProvides good basic information to direct soil improvement

Soil testing isn't very expensive or difficult to do and can be done anytime the soil is not frozen. Start by locating a soil testing laboratory. Nebraska soil labs are listed below.  

Contact the lab or visit their website to request a soil sample test kit and submittal form. Testing costs approximately $15.00 per sample.

Taking a Soil Sample
Unless there are obvious soil differences, one composite sample is usually sufficient. Another strategy is to sample areas separately based on their usage, so that samples are submitted individually for turf, ornamentals and vegetable gardens.

Create a soil sample by taking 10-15 soil cores from random locations within the sampling area using a soil probe. Or use a shovel to collect samples at a 5-6 inch depth. Remove any vegetation or thatch from the soil cores and combine them all into one container. This aggregate collection of soil is the sample. Place 1 to 2 cups of well-mixed soil in a plastic bag or the sample container provided by the lab.

Choose a test that will give results for residual nitrogen, phosphorus, potassium, organic matter, cation exchange capacity (CEC) and soil pH. Soil test results usually arrive in about two weeks, along with recommendations for soil amendments based on plant types indicated on the submittal form.


11. Understanding a soil test reportKey elements of a soil test report and what they mean

Nitrogen readings give a snap shot of the available nitrogen at the time of the soil test. Because of nitrogen's solubility it can leach rapidly from soil. This mobility causes nitrogen levels to fluctuate quickly, compared to other nutrients. Nitrogen is the nutrient most commonly limiting for plant growth. If a nitrogen reading is requested with the soil test, most soil reports will give a recommendation for nitrogen applications needed.

Phosphorus and potassium are usually present in high to very high amounts in Nebraska soils. Unless additional nutrients are needed for a specific purpose, fertilizers containing only nitrogen can be applied. Adding additional phosphorus or potassium will not result in toxic levels, but phosphorus runoff is a major contributor to algae problems in lakes.

pH is a measure of soil acidity, with an ideal range of 5.5 to 7.8 for most plants. pH influences soil nutrient availability and microbial communities. If soil  pH is outside the normal range adjustment may be needed. Lime is added to acidic soil to raise pH and sulfur is used on alkaline soil to lower pH.

Texture indicates the particles sizes making up the soil.

Cation exchange capacity (CEC) is a measure of the amount of positively charged ions a soil can hold. Higher levels of clay and/or organic matter in soil increase CEC. Soils with high CEC tend to hold onto nutrients better, while lower CEC readings indicate sandier soil which is more easily leached of nutrients.  CEC ranges: 0-8 sand, 8-12 loamy sand, 13-20 sandy/silt loam, 21-28 loam, 29-40 clay loam, >40 clay.

Organic matter (OM) is the end product of decaying plant or animal materials. OM in soil ranges from 0.5 to 10 % and provides several important benefits. Typically ranges from 2-5% in native Nebraska soils; 15% is ideal for vegetable gardens. Frequent tilling increases the rate of OM breakdown, resulting in reduced soil OM levels. 

  • OM improves soil structure by increasing soil microbial activity. Soil microbes in turn create a sticky "glue" that clumps soil particles (sand, silt or clay) into larger aggregates. A well aggregated soil is easier to work. 
  • OM improves the physical structure of soil by increasing pore sizes between soil particles, increasing air and water infiltration. Increased soil pore size makes it easier for plant roots to grow, since they can penetrate the soil easily. 
  • It acts as a storehouse for plant nutrients. OM has a very high capacity for holding cations, positively charged nutrient particles such as potassium, magnesium, calcium, sodium and hydrogen).
Exchangeable sodium (NA) is helpful if there is concern about the amount of salt in the soil. If the base saturation of sodium exceeds 5% water infiltration rates can be reduced and plant growth impaired. Excess sodium can be addressed with gypsum.

Micronutrients like calcium, magnesium, boron, copper, molybdenum, zinc, iron and sulfur very rarely need to be adjusted for field vegetable production or for home gardens.

If you have questions about reading the soil test results or potential soil amendments for your garden, call your local Nebraska Extension office.

Simplifying Soil Test Interpretations for Turf Professionals, Nebraska Extension
Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens and Landscape Plants, University of Minnesota Extension


12. Soil preparation for spring crops

Can still be done before soil freezes

Fall, or anytime into early winter when the ground is not frozen, is the best time of year to improve the soil in your garden beds for several reasons. First, spring rains often hamper a gardener's ability to get into the garden and work the soil as needed to prepare for planting. Fall preparation gets your gardens into a "planting ready" state, so you can begin a new gardening season whenever spring temperatures are favorable, and take advantage of spring moisture, which may be particularly important for gardening success next spring, since soils are so dry following summer's hot, dry conditions. Adding soil amendments in fall also takes advantage of winter's repeated freezing and thawing of the soil, to gradually mix and incorporate them.

Soil amendment, by incorporating compost, manure or other materials, is a good way to improve garden soils. The addition of organic matter improves drainage in clay soils and the water holding capacity of sandy soils. It adds essential nutrients and increases beneficial microorganisms.

However, soil amendment with manure must be correctly to avoid food safety issues in fruit or vegetable gardens. Only apply manures that have been aged for at least six months to minimize the risk of burning plants with excess ammonia. It is best to use manures that have been properly composted (to a temperature of at least 140 F.) to kill harmful E. coli bacteria that may be present in raw manure. Proper composting is critical for using manure in food gardens to avoid potential human illness. Manures from carnivorous animals should never be used. Additionally, if soils have high levels of salts, feed lot manure should be avoided as they will add to the problem.

Compost from lawn and garden plant materials carry a much lower risk of food pathogen.  But avoid using plants heavily infected with disease in your compost pile; disease pathogens may survive the composting process and infect plants the following year.

Using Manure and Compost as Nutrient Sources for Fruit and Vegetable Gardens, University of Minnesota Extension
Choosing a Soil Amendment, Colorado State University


13. Recycling Christmas treesShelter for birds, feeding station, mulch, fish habitat

Before taking your Christmas tree to the recycling center this year, consider that there are several ways you can put your evergreen tree to use in your own landscape. 

  • Use it to create backyard habitat for birds. Anchor the tree securely by setting the stump into the ground or a large bucket of damp sand, and securing the top of the tree with twine to nearby building, fence or trees. Your old Christmas tree provides excellent shelter for birds, providing protection from wind and predators. It can also serve as a feeding station, where you provide a buffet of food that our native birds love.
  • Add "decorations" - strings of popcorn, cranberries or raisins. Apples, oranges, leftover breads and pine cones covered with peanut butter then dipped in birdseed can also be added. Suet is especially attractive to insect-eaters such as woodpeckers, chickadees, and nuthatches and is a good winter energy source.
  • Cut your tree into branches and use them to mulch your strawberries or landscape beds.  The trunk can then be cut for firewood. Firewood quality from evergreen trees is only fair, but one tree will only provide a few logs.
  • Finally, if you live on a farm or acreage old Christmas trees can be sunk into ponds or lakes to create habitat for young fish.



Houseplants are susceptible to several common insect pests, including spider mites, white flies, scale, mealybugs, fungus gnats and thrips. Gardeners should inspect plants each time they water to look for signs of trouble. 

Houseplant Insect Control, University of Minnesota Extension
Managing Houseplant Pests, Colorado State University Extension