Thursday, February 4, 2016

Winter Tree Care - Stress Prevention & Insect Protection

Winter can be hard on everyone, even shrubs and trees! But if safety measures are taken, trees can be helped through another season. The shortage of water, fluctuating temperatures, drying winds, and other things make for a stressful winter, especially if plants are not indigenous to the environment they are planted in. Plants are harmed by cold damage through dieback, sun scald, frost heaving and root injury. So we should lend a helping hand to plants by taking some preventive measures. 


Water - Drought like conditions can be created by lack of running water and drying winds in winter. Roots are unable to replace moisture by absorbing water once the ground freezes and if the shrub or tree doesn’t have enough water stored to get it through winter, it may lead to leaves drying out and dropping or even dying. To avoid this, trees and shrubs should be watered till the ground freezes, that way, water to last through winter can be absorbed. 

Drainage - Providing good drainage is an easy way to protect shrubs and trees. Poorly drained, wet soil expands and contracts a lot more in winter and sometimes heaves roots out of the soil, but roots are kept in place by soil that is well drained. 

Mulching - Mulch is very useful for the following; keeping a constant temperature on the ground, helping roots avoid heaving through the soil and helps keep moisture in the soil. Also, biodegradable mulch will eventually break down and enrich the soil. Cover tree bases with about four inches of dry leaves to create mulch, chicken wire and fallen tree branches can be used to keep the mulch in place. A few inches should be left between the trunk and the mulch so as not to tempt burrowing animals to chew on the trunk. 

Wrapping - Trunks of trees can be wrapped to prevent winter damage. Young trees are vulnerable to frost damage, and even older trees can be nibbled by rabbits, deer and other animals. Barks can be protected from cracking by wrapping. 

Planting Location & Shelter - Planting trees in sheltered areas can protect them from wind and snow damage. Temporary shelter can be created if shelter is not readily available. This can be a burlap snow fence which blocks some wind and snow but let’s in sunshine. Snow should be knocked off before it freezes and causes damage to the branches. During winter, when plants are dormant, it is recommended that horticultural or dormant oil is sprayed to control insects. They should be sprayed on everything from lilacs to fruit trees. 

Difference between Dormant Oil and Horticultural Oil - The major difference between the newer horticultural oils and past dormant oils is that they are much more refined and they are useable throughout the year. Most horticultural oils are refined from petroleum oil. 

The refined oil is combined with an emulsifying agent; this allows the oil to mix with water which makes spraying easier. Originally dormant oils were heavier and less well-refined, however, they have been replaced with light weight, better refined oils that can be applied all year round on foliage without damaging it. The time of application is now why it is referred to as dormant oil and not the properties of the oil.

That said, there are other oils that can be used and they are; Mineral oil, summer oil, Supreme oil, Superior oil, Vegetable oil, Cottonseed oil, Soybean oil, and Neem oil.

Uses of horticultural oil:
  • They smother and kill insects 
  • They disrupt the feeding of insects which is important in stopping the spread of plant viruses by aphids. 
  • They can also be used against powdery mildew. 
Horticultural oils are effective, safe and they do not harm useful insects. Spraying should be done before buds swell and can be sprayed even if the buds are slightly swollen. This may damage some of the buds but the advantages overshadow the damage.

Precautions - Oils shouldn’t be used on oil sensitive plants and when temperatures are high (100° F) or very low. Also, if rain is likely to fall or the plant is wet then application should be avoided. Do not apply oils in freezing weather as it can cause the emulsion to produce uneven coverage. Finally, when shoots are growing, oils shouldn’t be sprayed. 

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