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Aside from breakage, does wind in freezing weather damage plants?

In hot weather, wind causes faster evaporation and can kill a plant by drying it out that way. How can air movement damage plant tissue at below freezing temperatures?

  • The answer is sublime - or sublimation, anyway. – Ecnerwal Dec 17 '16 at 3:44
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In general, wind chill on its own isn't an issue for hardy plants; however, wind chill combined with below freezing temperatures may cause problems in a few hardy plant stems and leaves. Air in winter (in colder regions) is already pretty dry, and that reduces the amount of fluid in soil and in plant stems; if there's a strong wind chill added on top, then dessication can occur on stems, causing damage to the cells which generally looks like whitened, shredded or fissured areas. Should this extreme wind chill damage occur, it isn't enough to kill a hardy plant, and will only happen on certain plants which may be growing in an area or region where the climate isn't quite what they're adapted for (grafted roses in Minnesota, for instance), or where the winter weather is much worse than would normally be expected.

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Not neccessarily - in fact often the opposite.

Wind Chill only affects us because we need to keep our bodies at a temperature of about 37 degrees centigrade - without a "core temperature" above ambient temperature, wind chill is irrelevant.

In fact, when it comes to plants, air movement often helps plants and is used commercially for frost protection.

I expect that if the air being blown over plants is cooler then the plants, it will cause the plants to release their heat energy to the air, thus becoming cooler, in a similar (but not as dramatic) way as wind chill on a persons skin.

  • Using fans or sprinkling water helps to SLOW the thawing of plant cells. Sometimes this is all that is needed to save plant material that is cold compromised is slowing the thawing process down so the cells don't rupture. Wind chill and air movement are two different things... – stormy Dec 16 '16 at 1:25
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    There's a difference between using moving air for frost protection and a strong wind chill in below freezing conditions - frost flows like water, which is why, on windy nights, even if the air temperature falls to 5 deg C, low enough for ground frost, no frost forms - the wind blows it around and prevents frost formation. But that's not the same thing as below freezing temperatures and a roaring north wind providing a -20 wind chill factor. 'Frost' and 'freezing' are not the same. – Bamboo Dec 16 '16 at 1:38
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    @stormy I respect your general growing knowledge immensely, but I am pretty sure that you are wrong about how spriinklers works. The energy required to change phase (ie from liquid to solid) is huge - think 100x typical energy, thus even very cold water requires a lot of energy [loss] keeping the cells in the leaves just above freezing even when the water is close to freezing point - effectively the water is adding enough heat to the system to prevent freezing. – davidgo Dec 16 '16 at 1:44
  • There is a point here I am sure I didn't clearly make. The PLANT leaves have frozen. If you can start a sprinkler before the sun comes up and the plant cells start thawing too quickly you can slow the rate of thawing and save some plant cells from bursting. The plant cells in the leaves are...slightly frozen. The sprinkler or air movement can slow the thawing process enough to save a plant cells. As well as adding some heat to the system. Anyway, that is how I understand this. Please question me more!! – stormy Dec 16 '16 at 3:17
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    Sprinklers shower cold water on the plant. But cold water still has more energy then ice. As the water that is sprayed cools down it releases heat into the environment so heating up the plant/tree. – Graham Chiu Dec 16 '16 at 6:01
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It depends.

Stems, trunks, branches are usually not affected, they are not humid, so no significant heat loss or humid loss.

For leaves I'm less sure. Winds remove humidity (as written by Bamboo, additionally alpine and nival plants have often hairs or they are much coriaceous or with specialised timing opening the stomas). Low temperatures will froze some liquids in leaves (depending of chemistry of plant, some are more reliant than other on low temperatures).

But there is nearly no combined effect, so "will chill". Plants don't heat themselves, so there is no combined effect about spending more energy for heating because cold temperature and wind. After a night outside, the leaves reach anyway the air temperature, so plants don't feel lower temperature because of wind. But there could be some more evaporation, but this is because of wind, not because of cold wind.

[Note: Contrary of the other people who answered this question, I'm much more used on humid cold (read: fog) and eventually hoarfrost also on high branches of tree]

  • I'm in the UK - problem here is damp cold, we lose plants to fungus and mould here.... Plus I had to laugh at your 'it depends'... ever noticed how often we all need to put that little phrase into our answers? Living things, individually, can't be entirely predictable, can they... – Bamboo Dec 16 '16 at 22:42
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I'd like to address this question from a physicist's point of view - sorry this is a bit long.

First important thing: heat moves from warm to cold; and the greater the temperature difference, the faster heat moves.

Wind chill is used to describe "feels like" temperatures - recognizing that when a wind blows, the air "feels" colder. Here is what is actually going on:

Objects lose heat through a number of mechanisms:

  • conduction: touch something cold, and you lose heat
  • convection: blow cold air over something, and it loses heat
  • evaporation: when liquid evaporates from a surface, it "takes heat with it"
  • radiation: you are familiar with the heat coming from a glowing fire - but even at room temperature and below, you lose "some" heat through radiation to the surroundings

In all these cases, heat moves from a hotter body to a colder body. Now when a body generates heat (like humans and other mammals), the rate at which you generate and lose heat must balance. We can sweat when we are hot (increase evaporation) or shiver when we are cold (increase heat production). How efficient these mechanisms are depends on several things. Convection and evaporation depend strongly on air flow.

When there is no wind, you will (slightly) warm up the air around you which then acts as a "blanket". Wind keeps replacing the warm air with cooler air, meaning you lose heat more quickly (because heat loss is proportional to the temperature difference). Wind chill is used to describe how this "heat stripping" affects warm bodies more strongly when the wind is stronger. It's not that an object will cool below ambient temperature due to the wind - just that it will lose heat more quickly. This is important for mammals who try to stay warm: if you lose heat faster than you can make it, you will eventually succumb to hypothermia.

For evaporation, the situation is a bit more complex still. Evaporating water actually "draws heat" from the surface. This is because not all molecules move at the same speed - and it's the fastest molecules that have the best chance of escaping. When the smartest person leaves the room, the average IQ in the room goes down a bit; when the hottest molecule in the liquid leaves, the rest of the liquid becomes a little bit colder.

This effect is more significant when the relative humidity in the air is low, because once relative humidity reaches 100%, moving the air around doesn't expose the surface to "drier" air. However, since the saturated vapor pressure of water drops very quickly with temperature, the rate of evaporation (and therefore the rate of heat loss due to evaporation) is much less when temperature is lower.

In summary: warm bodies (significantly warmer than the environment) will lose heat more quickly when there is a wind blowing. A cold (unheated) body will NOT, however, cool down all the way to the "wind chill temperature".

On balance, then, I would say the short answer to your question is "no".

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Wind chill blows away heat and moisture from a living tissue and in the process lowers the temperature of that tissue. The deciduous plants lose their most vulnerable parts, the leave. Conifers have tough leaves but wind chill could still damage their leaves. Heat is produced in the soil by decomposers working away all year long. Not so much in the the cold but still happening. Now if one keeps something moist with enough nitrogen big piles will steam all winter long. Decomposition produces heat. Maybe just enough to protect roots. Stems and trunks are the toughest, most protected part of woody perennials. The dead leaves of deciduous plants and perennials...helps to buoy up the snow forming pockets to hold the heat from decomposition. The dead leaves and other plant material also add heat because it was once alive, it is now dead and even in the cold will start decomposing.

Wind sucks! the accumulated heat away from the activity of decomposers. If there is a nice blanket of snow this snow helps to retain the heat.

When stems get frozen, and they will, if there is a sunny day, the side of the stem or trunk that gets the radiant heat from the sun will warm up too quickly and the the plant cells burst. Causing white on one side or winter damage on the sunny side of orchard trees, for example. This is the reason people paint the south side of orchard trees white to reflect the radiant heat and slow the thawing process.

Plants in dormancy do not need water. The plant has prepared for the winter, storing food, leaving tiny bits of vascular system feeding only the most important parts for survival. There is little that wind chill can compromise; no leaves, roots are protected and there is little transpiration happening in the stems so moisture loss is just not a worry. If the plant was not able to get enough food storage and proper hydration before dormancy, there is nothing one can do. Drastic wind movement will kill any plant material. Never transfer a plant in the bed of a truck without 'shade' cloth to slow the wind. Never use a regular solid plastic tarp. It will beat a plant's leaves even worse than the wind.

Wind chill can lower the ambient temperatures from above freezing to below freezing. It doesn't matter if it isn't below freezing. If temperatures are up into the proper temperatures for plants then you get proper temperatures for fungus. Moving air is the best prevention in this case. If temperatures get up above 90 degrees Fahrenheit, moving air lowers the ambient temperature and removes the newly produced O2 allowing CO2 to move in for use in the the production of food. 90 degrees plants start shutting down operations.

Using moving air during a freeze will simply slow the thawing process and will help save some frozen plant cells from bursting.

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