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Hort Update for Feb. 15, 2016

Lawns Major Symptom:

1. Snow containing de-icing salt

Flush soil in spring with water to leach salts

2. Deep snow and turfgrass

Snow good insulator, protects plant crowns
3. Plan turf renovation Soil preparation is key to success
4. Plan for saving water Water Saving Methods
Trees & Shrubs  
5. Dormant oil applications Apply in late winter before bud break
6. Pruning timing Prune shade trees from now until bud break
7. Sanitizing pruning equipment Clean tools between cuts to avoid spreading disease
8. Beware of super tree ads Tree ads that sound too good to be true, usually are
Landscape Ornamentals  
9. Benefits of snow Snow cover improves plant winter survival
10. Ice encasement damage to perennials May lead to soil oxygen deprivation and root death
Fruits & Vegetables  
11. Fruit tree pruning Best done from late February through March
12. Control fire blight and peach leaf curl during dormancy Copper fungicide applications made during the dormant season provides good control

1. Avoid piling snow with de-icing salts on turfgrass (or around trees and shrubs) - When needed for safety, use de-icing salts prudently. Before applying de-icing salts, wait until snowfall has ended and as much snow and ice as possible has been shoveled from pavement. Reduce the amount of de-icing salt needed by mixing it with an abrasive material such as sand. Richard Jauron, Horticulturist with Iowa State, recommends 50 pounds of sand mixed with one pound of salt.

Where salt is used, mitigate salt damage to soil structure and plants by heavily watering the area as soon as the ground thaws in spring. In runoff areas, 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 a few 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 eventually be needed.

Winter Deicing Agents for the Homeower, Nebraska Extension


2. Deep snow on turfgrass is typically not an issue, especially when turfgrass is already dormant when snow accumulates. Snow is a good insulator. It protects grass plants from extreme temperatures and plant crowns from winter desiccation. Where possible, avoid shoveling deep piles of snow onto one area of turf. Deep piles that are slower to melt can turn into sheets of ice that may smother turfgrass in spring, resulting in dead spots.


3. Plan turf renovation - While late summer is the ideal time to seed/overseed cool season turfgrass, it can be done in spring as well. Now is the time to make plans for turf renovation and reserving equipment that needs to be rented. Soil preparation is key to success. See instructions for "Improving lawns with significant thin or damaged areas" or "Improving the lawn through complete renovation" at the link below.

Improving Turf in Fall, Nebraska Extension


4. Plan for saving water in turf irrigation - Make plans for increasing irrigation efficiency this growing season. Water conservation is and will continue to be an important focus for turf and landscape management. Large amounts of water applied to lawns and gardens are never taken up by plants. Some water is lost to runoff; some water evaporates from exposed, unmulched soil; and the greatest waste of water is from applying too much too often; and irrigating during or soon after rainfall. Consider installing rain sensors for irrigation systems. And for information on water-saving methods for lawns and landscapes, see information on UNL's water website at the link below.

Water-Saving Methods, Nebraska Extension


5. Dormant oil sprays are applied to control insects and mites overwintering on trees and shrubs. They need to be applied during dormancy to prevent damaging plants. Dormant oils are best applied as late in winter as possible, when overwintering insects are at their weakest, but before plants begin to break dormancy. Pests controlled by oil sprays include scales, aphids, mites and some overwintering caterpillars and eggs. Air temperatures need to be at least 40 degrees before applying dormant oils. Temperatures should also be above freezing for 24 hours before dormant sprays are applied. Applications need to be made fairly early in the day. If applied late in the day and the spray freezes before it dries, plants can be injured. Follow all label directions and thoroughly cover branches and twigs for effective control.


6. Timing of pruning for shade trees and conifers - Shade trees can be pruned from now until just before bud break. Avoid pruning during spring growth. Pruning can be resumed in June and July. Avoid pruning from mid-August up to leaf drop. Spruce, Japanese Yew, Juniper and Arborvitae are best pruned just before new growth begins in spring. Also avoid pruning conifers during spring growth from mid-August into November. Pines need to be pruned after they begin growth; typically in June. Prune when the new growth (candles) have elongated but before they fully open. On shade trees, make proper pruning cuts and do not use any type of wound dressing on pruning wounds. A proper pruning cut is not made flush with the trunk. Instead, it is made outside of the branch collar, the thickened area where the branch meets the trunk, without leaving a branch stub.


7. Sanitizing pruning equipment - Some diseases are readily spread by pruning tools during the dormant season. Prevent transmitting diseases when pruning by sanitizing pruners and saws. It is commonly recommended to clean pruning tools with either a 70-percent denatured alcohol or a disinfecting solution of 1 part chlorine bleach to 9 parts water. Tools should be dipped for 30 seconds in solution between each cut. Bleach is corrosive to metal so before storing tools thoroughly clean with soap and water, rinse, and dry completely. Research has shown that Lysol can also be an effective disinfectant as well and is less corrosive.


8. Beware of super tree ads - Ads for what seem to be "super trees" appear in various publications at this time of year. Claims are made that the "super tree" will grow 10' or more per year. Beware of these ads. If it sounds too good to be true, it is. Two commonly advertised trees are Royal Paulonia or Empress tree and Austree. Both of these trees do grow extremely fast. However, because of the fast growth, they have brittle wood and are susceptible to canker diseases. Issues arise with the brittle wood and these trees are short-lived. A tree is a long-term investment. Make a wise investment by planting quality trees that add diversity to community landscapes.

Trees for Eastern Nebraska, Nebraska Statewide Arboretum

Trees for Western Nebraska, Nebraska Statewide Arboretum


9. Benefits of snow - Snow provides several benefits to landscape plants. As it melts, it provides moisture helping to prevent winter desiccation injury. We have seen a significant amount of winter desiccation damage the last two springs; this year's snow should help prevent that this year.

Since it is an excellent insulator, snow also provides plants and their root systems with protection from cold and wind. Snow depth determines how much insulation is provided; generally temperature below the snow increases by 2 degrees F for each inch of snow. In addition, soil gives off some heat, even in winter, so the temperature at the soil surface beneath snow can be much warmer than air temperature. One study found the soil surface temperature was 28F with a 9-inch snow depth, while air temperature was -14F.

Although green industry professionals and their clients get tired of dealing with snow and icy sidewalks, it's important to recognize the benefits of snow to our landscapes.


10. Ice encasement damage to perennials - Watch areas in the landscape near downspouts or where water pools for areas of ice. Long periods of ice encasement around the roots of perennials causes an increasing oxygen deficit in the underlying soil and may result in root or plant death. Make a note of areas in the landscape where ice accumulates for long periods of time; this might be a contributing factor to any plant problems found this spring.


11. Fruit tree pruning is best done from late February through March, before trees begin to break bud. Pruning should start on the most cold hardy trees first - apples and pears. Save pruning of less cold tolerant trees, such as peaches and nectarines, until late March. Make proper pruning cuts and use sharp pruning tools. Do not use pruning paints or wound dressings on pruning wounds.

When pruning to remove diseases branches, clean tools between cuts. If pruning out branches infected with fireblight be sure to get rid of the diseased branches and do not leave them on the ground near susceptible trees.

Pruning and Training Fruit Trees, Iowa State University

Pruning the Orchard, Utah State University

Training and Pruning Fruit Trees, North Carolina State University


12. Control fireblight and peach leaf curl during dormancy - Application of copper fungicide is an effective way to control fireblight and peach leaf curl when applied to dormant fruit trees during late winter. Bordeaux mixture, a combination of copper sulfate and lime, or fixed copper fungicides, such as tribasic copper sulfate, copper oxychloride sulfate and cupric hydroxide, can be used. Bordeaux mixture has the advantage of adhering to plants better during rainy weather, but it does stain surfaces and can cause plant damage if applied after plants have broken dormancy.

Bordeaux Mixture, University of California