I planted some lovely pansies the other day, right under my front window. It was 80 degrees out the day I planted, and the little guys have been doing quite well since transplanted.
But oh no, tonight's weather man predicts a possible frost overnight, and I am suddenly terrified about the poor pansies prospects of the possibility of getting covered in frost.
Hence the immediate need for hoodies for each of my fifteen Pansies that I planted prematurely, perhaps.
Made from a fine, silk like fabric that keeps the frost from landing directly on the poor delicate flowers. These teeny hoodies will surely save my babies from the torture of frostbite. Purplish, is the color I had in mind, it would go well with their coloring. Yes.-- blissmiss, Apr 23 2015 A picture is worth a thousand words. http://rutheh.files...011/04/pansies2.jpg [blissmiss, Apr 23 2015] plant cloche...to save your pansies http://www.amazon.c...Cover/dp/B004U49H7E [xandram, Apr 23 2015] I like this idea [+]. Please add pansie pants as well just because I like the way it sounds. (and liddle lamzy divey.)-- AusCan531, Apr 23 2015 [+] Can I have mine in white or gold ?
I will, of course, continue to read the title as "Panty Hoodies".-- FlyingToaster, Apr 23 2015 "We don't want chavs in OUR bed!"-- 21 Quest, Apr 23 2015 I think you will find that frost doesn't "land on" anything, any more than dew lands on something, or condensation on the outside of a glass of ice-water "lands on" the outside of the glass. All three have something in common, though....
An item exposed to cloudless sky at night tends to radiate heat easily, and becomes colder than the air temperature. That coldness causes condensation of atmospheric humidity. If it gets even colder, the condensation will freeze.
So, all you need is a kind of cover over the whole flower bed, to reflect radiation back down to the flower bed. Try some "space blanket" material.-- Vernon, Apr 23 2015 Aha, you are so right, Sir Vernon. I forgot the science behind the necessity. Thanks for bringing me back down to Earth.-- blissmiss, Apr 23 2015 EEekkks, [xandram], more plastic? And on the day after Earth day??? Soft, warm fabric much more Earth friendly. And prettier too, my friend.-- blissmiss, Apr 23 2015 //colder than the air temperature. //
Seriously? Can you back that up? (Evaporative cooling doesn't count.)-- MaxwellBuchanan, Apr 24 2015 [MaxwellBuchana], is no a glass that contains ice-water colder than the air temperature? And I'm sure you know that condensation happens very easily on the surface of the glass.-- Vernon, Apr 25 2015 // These teeny hoodies will surely save my babies from the torture of frostbite. //
Flamethrower ...
Gets rid of weeds, too ...
// Purplish, is the color I had in mind, it would go well with their coloring. //
Flamethrower. Lovely red/yellow/orange ...-- 8th of 7, Apr 25 2015 //is no a glass that contains ice-water colder than the air temperature?// Yes, what of it?
You said //An item exposed to cloudless sky at night tends to radiate heat easily, and becomes colder than the air temperature. // I disagree.
If I have a rock sitting in air at 1°C, on ground which is at 1°C, I contend that the rock will eventually reach 1°C. In this mansion we obey the laws of thermodynamics.-- MaxwellBuchanan, Apr 25 2015 Eventually? The temperature may have changed by that time!-- po, Apr 25 2015 "If we don't clamp down hard on these hoodies, we'll soon be up to our balls in crusty jugglers!"-- 21 Quest, Apr 25 2015 [po], it's good to see you back here, and congratulations on your release.-- MaxwellBuchanan, Apr 25 2015 I'm sorry [Blissy] - for some reason I thought the cloches were made of glass!-- xandram, Apr 27 2015 Hey xanie, it happens to the best of us. My pansies made it through the night and are as strong as ever. All praise to the Pansy.-- blissmiss, Apr 27 2015 Pansies actually contain a protein which inhibits the formation of ice crystals. Therefore, they are one of the few flowers which can survive temperatures as low as -20°C.-- MaxwellBuchanan, Apr 27 2015 No, wait - that's Antarctic Garrfish. I always get them confused.-- MaxwellBuchanan, Apr 27 2015 So my Antarctic Garrfish will be all right over night in the garden then?-- tatterdemalion, Apr 27 2015 I can guarantee it will lose no petals.
Incidentally, [bliss], did you know that pansy flowers contain a higher concentration of phenaldenone than betel nuts? 12 flowers (or flower buds) are sufficient to induce hallucinations.-- MaxwellBuchanan, Apr 27 2015 No - wait. That's cane toads.-- MaxwellBuchanan, Apr 27 2015 Whahhh, now you tell me. I already ate the garden...-- blissmiss, Apr 27 2015 Don't worry. A garden can regenerate from as little as 1/500th of the original.-- MaxwellBuchanan, Apr 28 2015 No - wait. That's planarians.-- MaxwellBuchanan, Apr 28 2015 //An item exposed to cloudless sky at night tends to radiate heat easily, and becomes colder than the air temperature. // I agree. If I have a low thermal mass object (say a leaf, not a rock) that has low thermal conduction to the ground (which is at say 2°C), in still air that is at 1°C, and it is a cloudless night, the air, which is fairly transparent to infrared light, may not be cooled by radiation as much as the leaf.
I found several statements online supporting this, but didn't find any that were "authoritative". Several of the site that I thought might be considered authoritative (Wikipedia, Cornell extensions) mentioned cooling through radiation but stressed the settling of cold air near the ground to explain frost forming on the ground when the air temperature a few feet above the ground is above freezing. However I would like to point out that water will not condense on an object that is warmer than the surrounding air. If an object cools below air temperature due to evaporation, that indicates that the air must be dry enough that dew/frost is not going to happen. Typically the ground is warm compared to the air at night. Therefore the only possible explanation for frost or dew is that radiation makes the leaves colder than the air.-- scad mientist, Apr 28 2015 //Therefore the only possible explanation for frost or dew is that radiation makes the leaves colder than the air.//
To quote a Yorkshire acquaintance, "ah don't bloody believe it."
For one thing, heat transfer by conduction will overwhelm heat transfer by radiation, at those sorts of temperatures.
For another, everything around the leaf (or whatever) will be emitting radiation corresponding to its temperature.
Try the following thought experiment. Take a [dry] thermometer outdoors on a clear night, and wait until it gives a steady reading. Now take a piece of black card (which you have allowed to cool to ambient temperature) and hold it a couple of feet above the thermometer to obscure its view of the night sky. Does the thermometer show an increase in temperature?-- MaxwellBuchanan, Apr 28 2015 I heard that plants breathe out at night, releasing CO2... which sounds like they're burning something, so I'm gonna vote for "warmer".-- FlyingToaster, Apr 28 2015 // plants breathe out at night, releasing CO2 //
Plants have lungs? Are you talking Triffids here ... ?
// Does the thermometer show an increase in temperature? //
Is this before or after you set fire to the piece of card with the flamethrower ?-- 8th of 7, Apr 28 2015 // Take a [dry] thermometer outdoors on a clear night, and wait until it gives a steady reading. Now take a piece of black card (which you have allowed to cool to ambient temperature) and hold it a couple of feet above the thermometer to obscure its view of the night sky. Does the thermometer show an increase in temperature? //
Yeah. That's why the car under the carport doesn't get frost on it while the one outside the carport needs to have its windows scraped. It would be interesting to do the experiment with a thermometer too though.-- scad mientist, Apr 29 2015 Hmmm. Possibly a good point, though the carport roof and walls will probably be radiating a little heat.
However, I am now uncertain, I think. Possibly.-- MaxwellBuchanan, Apr 29 2015 Next time I'll just park my pansies under the carport, me thinks.-- blissmiss, Apr 29 2015 //Are you talking Triffids ?// I don't go near the Triffids at night: some of them are insomniacs.
CO2 released by plants at night could just be backwash, but it would hardly be worth mentioning if it was.-- FlyingToaster, Apr 29 2015 random, halfbakery