Wind chill effects on tropical plants?

The conventional wisdom says that wind chill has no effect on plants (other than causing dehydration in some needled conifers). My experience and observations seem to indicate that the conventional wisdom may be incorrect.

We recently had a couple of nights in NE Florida with temperatures down into the upper 20s for some sustained hours. As I have noticed in previous winters, the same species of plant placed in different locations has completely different responses to the freezing temperatures. In most cases, I can trace the path of wind gusts that come by and "blast" the plants in the path of the winds. This usually happens when the wind whips around the corner of buildings or is otherwise channeled, or has a clear, unobstructed path and can keep up momentum.

Many of you may be growing tropicals in pots and already have them in greenhouses or bring them indoors for winter, so you may not have any input on this; but for those that do grow tropicals outside, I'm wondering if you've noticed a similar effect? I just don't know how to otherwise explain that the same species of plant can do fine with the winter temperatures and another not more than about a foot away can end up brown (I can get some photos of anthuriums in my garden to document this). I do know there are a lot of factors that can affect micro-climates -- proximity to water, nearby concrete foundations or other surfaces that hold heat (I've had impatiens remain fresh and flowering throughout the winter by planting them against a south facing concrete block foundation of my house), protection by overhanging trees or eaves, etc. But when two plants of the same species in just about the same location have different responses to the freeze, it seems something else other than micro-climates must be having an effect. I suppose to some extent it depends on the specific health and freeze resistance of each individual plant, but that, too, seems like a stretch.

I'd be interested in hearing reports of your experiences, observations, and theories on the topic of wind chill and tropical plants (with "tropical" meaning just about everything that will grow around Zone 9a and higher).

BTW - I did some experiments to see what measures work best to keep plants from freezing. It turns out that "twinkle" lights are very effective, especially when combined with a cloth cover. I have three Ficus benjamina trees outdoors in basically the same area near my front porch. One I covered with about 200 twinkle lights and an old curtain, another I covered with the same fabric curtain with no lights, and another with no cover nor lights. The one with the lights and cover came through with barely a twinge of freeze damage! The one with a cover but no lights had the top leaves burned, and, as to be expected, the one with no cover nor lights had most of the leaves blasted off. The official position of our local Extension Office is that covering plants with sheets or other fabric is a waste of time because it can only keep the temperature up a degree or two (but it seems that one or two degrees can make the difference!) I was skeptical about the twinkle lights really providing enough heat to matter, but my experiment convinced me that they definitely work when combined with some fabric to help hold in the heat.

Thanks for reading my (as usual) loquacious post!

Jeremy

Wind chill can definitely have an effect on whether a plant gets damaged--wind has a dehydrating effect on all plants not just conifers, and a well hydrated plant is going to show less frost damage than one that's not quite as well hydrated. So if you've got two plants that are borderline whether they're going to show damage or not and one of them gets a bit more wind than the one next to it, I wouldn't be at all surprised that the one that got a bit more wind showed more damage. Especially if the plants are in a bed near the house, even if they're right next to each other they could experience different levels of wind depending on how the wind moves as it bounces off the house. It's not as simple as whether it's in the direct path of the chilly blast or not, there's lots of turbulent air flow going on as the wind hits your house or other objects in your yard, and this could very easily create slightly different microclimates that are very close to each other. And sometimes the still areas where cold air can collect are the worst places for frost damage--a little bit of air circulation in an area can sometimes prevent frost damage (we never get frost on windy nights, it's always the clear nights when the air is still)

Then on top of the minor microclimate differences between the two plants, there are also going to be subtle differences between 2 plants themselves that can contribute--if you're in a borderline situation where a plant might get damaged or might not, even something like a slight difference in the level of hydration or overall health of the plant could be enough to make one get damaged and one not. Or in climates like ours where plants will sometimes put out new growth during the winter, if one plant's leaves are slightly newer than another's that could be another factor

So you put all these factors together, combined with a temperature that's borderline on whether it'll damage the plant or not, and you can see things like what you're seeing. If the temps got a bit colder, then those subtle differences in microclimate, hydration, etc won't have as much of an impact because everything will get damaged, but when you're in a borderline situation they definitely could factor in.

I'm a plant collector, so I tend to have one of everything rather than multiples, and the things I have multiples of tend to be things that are a bit hardier so unfortunately I don't have too many personal observations--the only example I have was last winter I had 3 newly planted Pittosporums (which should have been thoroughly hardy here). Even though they were close together, one was farther down a hill than the others, and of the two that were on a flat section of yard, one was protected on both sides by trees/house and the other was only protected on one side. So there were clearly different microclimates that could come into play (the only one that wasn't severely damaged was the one that was in the flat part of the yard with protection on both sides)

I have one section of the yard in which a fence seems to block a lot of those winds. Additionally, there are quite a few plants nestled closely together and also a pond. The entirety of all this has created a "microclimate" in which I can grow things there that I can not grow in other areas of the yard.The same plant that remains green in that area, is ruined in another area.

it is my understanding that windchill makes it colder for heat-generating organisms
because it displaces the heat they generate. I didn't think plants generated heat.but maybe some do?? I would think that might have been studied somewhere.

With plants, it's about dehydration, not taking heat away from them. Wind has a dehydrating effect, and dehydrated plants are more easily damaged by cold.

I believe there are a few plants out there that do generate heat (I forget which ones off the top of my head, but I remember reading about at least one that did). But the majority of them don't to the best of my knowledge.

Jeremy, I used your idea about Christmas lights during the freeze two weeks ago. I have a Roebelenii Palm bracketed by some Anthurium and White Birds of Paradise, which I wrapped together (they are at the top right hand side of the picture). I then threw in about three strands of Christmas lights under the cover. After the freeze, the Palm and the Bird of Paradise appear to be doing fine, but the Anthuriums have lost about half their leaves. In walking around the neighborhood it looks like most of the other Palms and Birds of Paradise did alright, even the ones that weren't covered, so it's not clear whether my covering those plants or using the lights made any difference. I had thought that by planting the Anthurium close to the house and using a cover along with lights, they would come through unscathed, but that was obviously a wrong assumption. So I'm not convinced the Christmas lights do work (at least in a freeze where the winds quickly dissipate any heat). On the other hand, when the temperatures get below 32 degrees I get desperate and I'll try anything. So I'll likely keep experimenting with them to see if they help.

I don't know how I missed this a few weeks ago when Naples was forecasted to get frost. I have a dozen or so orchids rooted to the palm trees in my front yard. I keep my Christmas lights up on these trees and then pin pillowcases around the trunks at each orchid. I didn't even lose petals. It works great. I think in the northern climates it would be better to use the older style bulbs that produce more heat. Remember getting burned as a kid if you touched them? Just remember your plants can get burned too! The temperature appears to be dropping again!

Thanks, TeriChris, for the info. I did some experiments in the Jan. 2 - 3 artic chill we got in Florida. I found that twinkle lights were effective, especially when combined with a cloth cover, in providing frost and freeze protection. I am finishing up an article for DG about the results and reporting what I found in researching the topic. I hope to have the article finished this weekend and it should appear on DG within a week or two. I'll post here when the article is published.

Great news about your orchids. I had a Phillipine Ground Orchid, Spathiglottis plicata, in the ground that was in bud at the time of the freeze. The twinkle lights kept the flower bud from getting blasted by the freezing temperatures.

Jeremy

Jeremy

jGood morning all - this winter I did experimenting with water and it's affects on plants. During that time that Jeremy was talking about, it was a few degrees colder here in Lake City as we are farther inland and I am out in the country and not in a city. The temps during these 3 nights were in the 30’s/teens/20’s.
I was amazed on what made it thru these temps and what didn't. The plants that I had in the ground and that I covered with large pots over the weekend before the freeze hardly got burned at all while the other plants that I hurriedly covered with pots on Tuesday right before the cold weather came actually received more damage. I even had thunbergia vine (black eyed Susan) that I had some parts uncovered as the wind blew off the sheet and the vines that were close to the ground and close to trees that actually didn't get touched and looks fine and continues to bloom!

I debated on moving all my cuttings from my redneck hot houses into the greenhouse before the freeze hit, but I stopped myself as this was supposed to be an experiment for me and I needed to find out if these things worked, before I spent time and money making more hot houses. Well, the cuttings I had setting in trays over the buckets of water in the A frame all look great with no damage at all and these are the wandering jews which are more of a succulent type plant. I thought these would be doomed.

The cuttings that I had in the compost bin covered with plastic, some of the stuff was damaged and some was not touched at all????? Most of the tops of the coleus cuttings were burnt but toward the bottom, I still have good growth and no damage. Some of the other cuttings of different plants weren't bothered at all. I think if I would have had water containers set inside, I wouldn’t have had so much damage.

On the steps hot house the same thing, I had containers of water placed around and those plants that were close to the water were hardly touched and those farther away were damaged more. All the cuttings I had under the plastic bottles seem to be fine.

In the greenhouse most of the taller brugs and plants had damage, while those shorter and closer to the ground were fine, which doesn't make sense at all as I thought heat always rises to the top???? I had lights on in the greenhouse all three nights.

The plants and cuttings that I had in my raised bed boxes that I just covered with a frost cloth are not damaged at all and look untouched. I'm sold on that stuff and will be buying more.

I have tried twinkle lights in the past with alot of success, but I have a few big dogs and not enough extension cords to hang these all over so I try to save those for the beds I have closer to the house.

I am convinced that the water/moisture helped this year with my experiment.
Judy

Great experiment, Judy! What did you have the water in? Was it just buckets/open containers? Also, good news on the frost cloth. I forgot to mention it in my DG article (which is still in the draft phase because I keep editing!). I will mention the frost cloth there. Did you happen to do any photos that I might borrow for the article?

Has anyone used "space blankets?" I found that phrase covers a wide variety of materials -- everything from thin mylar sheets at 99 cents to composite/layered fabrics for around $20 - $60, depending on size and quality. From some experiments done by the Univ. of Colorado Extension Office, the composite/layered space blankets with an aluminum cloth reflective side can hold enough heat to keep the temperature up about 30 degrees F over ambient air temperatures.

When I came across the Wall-of-Water product discussed for protection of things like tomato seedlings, I wondered if the same thing couldn't be achieved by encircling a seedling in a pot with 2-liter soda bottles filled with water?

Jeremy

Jeremy - my son has his own paint/construction company in Jax and I get all the 5 gallon used paint buckets I need - that is what I used in the make shift A frame to set the trays of propagated wandering jews on. I set them outside to fill with rain water- then topped them off with the hose. My husband also gets these 5 gallon metal containers from work that they just throw away - they are painted inside and I have him bring them home and give them away to other gardeners. If you want I can try to get you some next time I come to Jacksonville.

I've got an old camera - I'll try taking pictures and emailing to you. I'm not very good at it but will try, can you give me a day or so???

It started last year, when I added about 8 -10 buckets of water around my greenhouse for the winter. And I noticed that hardly any damage was to my plants. So this year I took it one step further with buckets of water in the hot houses. Actually looking thru the garden catalogs and seeing those Wall of Water containers aroung those tomato plants was where I got the idea. Next year, that is the experiment I wanted to do was to put containers of water around plants before I cover with the frost cloth or blankets.

Judy

Thanks, Judy, for the info! I'm still plugging away on the frost/freeze protection article and can wait a few more days to submit it. I think I've got the idea of what you are doing, but any photo would help. Though the quality of your photos may be as good (or better!) than what I can get with my old Polaroid digital that was one of the first digital cameras offered for retail sale, if for some reason your photos aren't usable, I can always repeat the process at home for illustration purposes.

By the way, to all, I've still not come up with any definitive answer as to whether plants experience "chill factor" from winds. The closest I've come is a statement by the University of Arizona Extension Office that said "cold winds can compound the damage to plants" without explaining how or why. The process, from what I can gather and as others have said here, is the cold wind can further dessicate plants and thereby contribute to frost/freeze damage.

Jeremy

Just a few of my thoughts on your experiments juja. a lot of what you are seeing is the effects of the heat radiating from the ground. if you have a week of 60 degree weather and then all of a sudden you get a snowstorm, the snow will melt until the ground temperature becomes cold enough to support the accumulation of snow.
the water would be somewhat similar. it would take a bucket of water longer to freeze than a glass of water, and i would guess the water would act as an insulator. If you had a plant that could withstand 32 deg. but not 20 deg. you could probably spray the plant with water, letting it freeze at 32 deg to provide an insulator for a short time from the 20 deg air temp.

I live in Kentucky and my father grows some very cold tolerant palms. Years ago we had a very cold blast hit us out of no where my father took wet sheets and covered all the palms and plants. The sheets froze over the plants making a protective iglue. It really helped protect the plants for that short time.
On another odd note I grew the very tropical Java fern usually found in aquariums in a waterfall I built. That winter sense the waterfall was on all winter the plant survived unscaved. From what I gather it is a zone 9 to 11 plant but it never did freeze in its situation though the water temps were extremely cold.

Actually, from what I've read, Len, the effect that a Wall-of-Water or Judy's buckets would have is that (by some principle of Physics that is way beyond my understanding) water releases heat as it freezes, thereby providing some additional warmth in the area immediately surrounding the water. You may be correct, though, that part of what Judy observed was stored radiant heat from the sun that is released when the air around the soil is cooler than the soil. I suppose to know for sure, her experiment would have required some plants with water buckets nearby along with the same plants on the same type of soil/floor with no water nearby. Also, from what I've recently learned from research for my article, the idea that a plant with ice on the leaves will not go below 32 F is apparently incorrect. The ice will probably do more harm than good because the temperature will continue to drop past 32 F and the ice will pull thermal energy out of the plant leaves by conductive heat loss. The notion that a layer of ice can protect plants probably sprang from the agricultural use of fine water mists sprayed constantly at a consistent rate for the entire duration of freezing temperatures. This technique, also, works on the law of Physics that water releases heat as it freezes. In order for the fine water mist to be effective, however, there must constantly be some portion of the water that is in the process of freezing -- that is why it is necessary to keep the water flowing at a consistent and constant rate. The mechanisms and engineering are so intricate and precise that it is not the sort of thing the average gardener could do at home.

I welcome differing opinions or additional information because I'm trying to get the facts straight before submitting the article!

Jeremy

If humidity levels are not figured into the calculations for windchill, how can dessication in plants be measured? of course i've also read that winds can actually trigger the stomata in a plant to close, thereby countering the effects of plant dehydration.
I

Thanks for all your comments - next year I will use the same plants in different areas to see the affects correctly, I sometimes do things on impulse and don't think thru. I haven't got a clue when it comes to Physics, I'm just trying to push the zone here and keep my tropicals alive and looking well during the brief cold snaps we keep having here in North Florida.

Jeremy your right on constantly sprinkling water on plants during a freeze, as we were at the Research Center in Live Oak a couple of weeks ago and they explained that to us, that you needed to have the sprinkler running constantly to have success.

I'm not sure I can help explain the "wind chill" factor on plants, I have been looking at and defining the little micro climates thru out my yard this year, I was amazed on what plants came thru with little or no damage and the same plants a few feet away had damage. I even had a clerodendrum (I'm not sure the name) but the stalks on it grow over 8 foot, all the tall stalks were damaged and leaves burnt, but the new growth on the plant (3 foot stalks) are untouched. That could be from the heat radiating from the ground.

Judy

Hey Jeremy,

I'm glad you posted this thread, because I have notice these differences. I know now to fortify everything on the West fence Area, as they are the first to suffer dammage. I have also noticed a difference in the plants response during dry freezes, and the freezed following a rainy period. The plants fare much better after freezing conditions when there has been no precipitation, and seem to exibit more dammage when the weather has been wet and rainy. I always thought the opposite.

I do agree with Ecrane about the micro climates. This I know because my garden has a multitude of Micro Climates, existing in a Microclimate part of town. Because of this, it's very difficult to make sense, pre-plan etc.
I pretty much have started going by the "feels like" temperature. Whether the plants experience that or not, it at least provides me with a more successful barometer in pre-planning some of these events.

Thanks for the tip on the lights...I have boxes of them I never use!

Rj

Rj--I've had exactly the opposite experience in terms of freezes during dry times or when the ground's wet. The wetter the ground, the less damage I typically see on my plants. As a matter of fact, if I know we've got a cold night coming and we haven't had any rain in a while, I'll go out and water the garden in the late afternoon/early evening to minimize the damage. Wet soil holds more heat than dry soil, so I'm puzzled why you're seeing the opposite. I suppose it could be something to do with climate differences though--around here if it's actually raining, it never gets anywhere close to freezing temperatures, so if you have freezing temps and rain at the same time maybe that has some sort of different effect. But on our clear dry nights where it gets down below freezing, I've definitely had better luck if my garden was wet going into it.

Well, what I'm referring to is precipitation. I water things thoroughly too when it's been dry, and I'm wondering - does the amount of water play a roll? A week of cold wet rain, probably sets the conditions for a longer colder freeze..A week of cold (but not freezing) dry weather might need a longer time to when dipping below temps, therefore not dammaging plants..and what I mean by dammage are mainly defoliating. A couple weeks ago, we had freezing temps for a few hours, but I thought things would be okay..because it had rained for a week, yet certain things suffered dammage, and even some parts of the same tree were fine, some parts not (Papaya).
Another factor that I think Plays a roll - is that our regions are not typically subjected to more than a night or two of freezing, then the temps are back up. I definately notice it messes with the plants when the morning starts out at 29F and is 60F by noon.
So many little factors, and I know what your saying about root dammage, I just wonder about the surrounding weeks condition and the rooll alot of precipitation plays.

I was actually talking about foliage damage not root damage--it never gets cold enough here for the ground to even come close to freezing, so any damage I get is always to foliage not roots. I don't know how to explain the differences between what you're seeing and what I'm seeing, maybe it's because we never have rain and freezing temps at the same time, so I don't know what would happen if that was the situation. But it just shows that things are different in different climates, so everyone needs to figure out what works for them.

Thanks for reviving this thread! I've been working for weeks on my Dave's Garden article about frost and freeze protection, mostly confined to my experiment with twinkle lights on some of my Ficus benjamina and some of the Ficus without twinkle lights, as well as the positive effect the lights had on protecting other tropicals. Then.....I started finding more and more bits and pieces of suggestions and recommendations about frost and freeze protection scattered all over the Internet, but not all collected together in one website or document. I get fascinated by following a research trail, and just keep reading and reporting. My article for DG, which is generally supposed to be in a 400 - 1,000 word form has turned into a small novel. I've spent the last two days at the computer (missing out on the beautiful weather we have right now) from dawn to falling asleep at night, trying to wrap it up the article. I'm determined to push on through and hit "submit!"

O.K., my obsessive/compulsive mania aside, I did find in my research that just about everyone recommends soaking the soil around a plant immediately prior to a freeze (with a few exceptions for those plants that would suffer from soggy soil in cold weather). As ecrane mentioned, the wet soil can release latent heat as the water freezes. I only recently learned that this is recommended and don't have any experience one way or the other with soaking my own plants for a freeze, but intend to do it with our next artic cold snap (hopefully, not until NEXT winter! LOL) Some people even recommend letting a hose trickle around the base of a freeze-sensitive plant for up to 3 days of freezing weather. Again, there is 80 cal of heat released for each gram of water that freezes.

We also never get cold enough here for the ground to freeze, so I also don't have to worry much about root damage from cold.

rj, one difference may possibly be the plants you are growing there may be much different from what ecrane and I might grow. If you have a preponderance of cacti and succulents, they definitely would not be happy in cold, wet weather. Just a thought.

BTW - despite lots of searches using all kinds of key words, there doesn't seem to be any one that states whether "wind chill factor" affects plants. For the article, I'm going with the answer of "no, it doesn't," based on our discussion here, but am inviting readers of the article to come to this thread and post any info or opinions they may have on the topic.

Thanks for all your input!

Jeremy

Could be. Usually it's palm trees, brugs and Papaya trees. My friend Phillip and I discussed the subject tonight. We figured it's probably because after a 3 or for day 40F precipitation followed by freezing temps- that it's because temps drops faster, and is below freezing a bit longer. Sort of follows the logic that taking a glass of water from the fridge to the freezer would be quicker to freeze, than tap water...but then does it really? I always heard tap water would freeze faster. I'm sure I'm missing a few pieces of the component variable puzzle!

and don't forget also that plants are living things and many times they can do things to adapt, like putting a little anti freeze in the sap.

OK guys, I'm am definately NOT wanting any more cold weather this year, but believe me with all these ideas, etc. I am definately going to be doing alot of experimenting next year in my yard with stuff.
I'm still trying to figure out how to determine the wind chill factor into this and figure out an experiment.

Also, where I live the ground never freezes. I'm a "push the zone" gardener and some plants classfied as tropicals that are in the ground have really done well in my yard with the extra care I give them during the couple nights of dipping temps.

Jeremy be sure to put a "To be continued" line at the end of your article as next year, we need to get together and really try some of this stuff.