Tuesday, February 7, 2012

Radiant Heating in the Winter

Though I have been gardening but a few years, as I have been doing so I have noticed that the climate here in Tucson is warmer than the catalogues that said “Zone 8” on them stated. Other than last winter when we had an unseasonably cold 15 degree Fahrenheit Temperatures (and all of Tucson was having their non-insulated pipes break) the temperature usually only dips near freezing at night for a couple of weeks. Given what I have experienced the last couple of years it is about time the USDA changed their map to better reflect more recent climate trends.

Given the unseasonably warm weather this year and finding that the weather forecast had no chance of freezing any time soon, I decided to transplant three of my tomato sets into the summer garden to see if I could get a jump on the season. I set out two of the plants with plastic around them to heat up the ground and the third I did not cover, but just set a milk gallon jug full of water next to it. The sun is now coming up before 7:30 so it should be warming up, right?

Left plant-was covered, Middle Plant-covered, Right plant-no covering.

Wrong. Just the other morning I found that the cold had really nipped at a couple of my tomato plants. So I cut them back. Then I noticed something else. The plant with the water next to it had no effects from the freezing while the other two did. I have noticed in the past that little tents or conches do little to stave off the effects of freezing and I have noticed that clear or opaque water containers help tomato plants from freezing but I have never seen this so clearly demonstrated. The practical science behind this is that the water bottle absorbs heat during the day and releases it at night. The more water in containers, the more balanced temperature should remain.

For future reference - I will definitely make use of soda pop bottles and milk bottles (filled with water) to get an early start on the season. I’m glad that I could make this mistake so that others (and hopefully I) can learn from it.

14 comments:

  1. Wow. You've discovered a trick that I am anxious to try. It's always a gamble here to set your tomato plants out. Frost sneaks in after even the warmest of days. I'll try this idea in the Spring... always looking for a way to jumpstart the tomatoes!

    ReplyDelete
    Replies
    1. Thanks for the response. I’ll have to keep you updated on if my plants continue to live. The earliest day we normally begin to set out tomato starts here is February 15th. However, this year has been rather warm and we haven’t had nearly the dramatic ups and downs in temperature as we have had earlier years. You’ll have to let me know if your Hardiness Zone changed based on the USDA map as well.

      Delete
  2. Very interesting! Might have to try that one when it gets closer to planting weather - we always have a few late cold spells!

    ReplyDelete
    Replies
    1. Thanks for the reply. I would not have tried planting early if I didn't have extra tomato plants in my greenhouse. As a precaution, I always plant more in case I lose half the crop.

      Delete
  3. Have you tried using/painting containers black? They'll absorb and radiate heat better. I've read of fairly large greenhouse owners using barrels and hundreds of gallons of water as thermal mass, some even going so far as to run the water through black piping on the roof to speed its warming.

    ReplyDelete
    Replies
    1. You have a really good point, James. I have heard that darker colors absorb light better. I have tried dark colored containers and found that, at least for me, they have not absorbed heat as well as clear containers. Perhaps clear containers, which allow light through, can keep from shading off the ground and plants I am trying to warm up. A professor in an environmental class in college informed me that it is not only the color, but also the surface texture and the composite that the material is made of that determines its ability to absorb and transfer heat. I am afraid that if I try food coloring, to test if colored liquid would increase the heat, that the coloring may eventually settle to the bottom. If you or anyone else has any ideas of how I could keep food coloring suspended in a water jug, I’d love to hear it. This would enable me to determine if it would make a difference to isolate the color of the liquid on the inside of the container instead of changing things on the outside.

      Delete
    2. I can't say I've ever had a problem with food dyes and the like settling after dissolving them in a liquid, but then I haven't ever left them lying around for weeks! I imagine a greater problem would be sunlight (specifically UV) slowly breaking down pigments.

      You could perhaps try something inorganic, perhaps copper sulphate (I'm trying to think of something darker, but my mind is blank for now)? I wonder how long-lasting squid/octopus ink would be.

      Another thing you could try is perhaps just painting the bottom part (perhaps 1/3rd) of the container, which would still leave light fairly unobstructed, but wind up with a "solar panel" at the bottom, sucking in that energy and converting it to heat. The convection that would generate would likely lead to fairly even heating inside the container too.

      Of course, a few thermometers in some different test vessels would quickly give you a "scientific" answer! :)

      Delete
    3. Oh, and a further variable might be to coat the inside of the container with paint (use spraypaint, or put a little "puddle" of dark (matte black) paint into the bottle and swoosh it around, draining off excess, then leaving to dry before filling).

      Delete
  4. Nice trick. Radient heat has been around for a long time and who knew the tomatoes would benefit so nicely. Thanks for stopping in on Green Apples and welcome to Blotanical too.

    ReplyDelete
    Replies
    1. Thanks Donna. No problem about stopping by your blog. I am excited to be part of the community at Blotanical.

      Delete
  5. Jay, I enjoyed my visit to your blog. Love Arizona, can never get enought of your gardening. Here along the shore of Lake Michigan - it is sooooooo different! So the visit to your blog is a great change especially during Winter. Jack

    ReplyDelete
    Replies
    1. Thank you for the complement, Jack.

      Around June I'll be wishing I live up there. That is when we get the "blow dryer" effect here. With the wind and the heat in June you literally feel like you are getting hit by a blow dryer.

      Delete
  6. Here's another trick: In late fall, I gather all my tender containerized Jasmines into an area protected from North winds. I buy black wash basins, fill them with water, and put them all around the south side of my cluster of tender container plants, and then a few amongst the containers. Then I make a tent of my Aluminet radiant barrier cloth and for 3 years, as long it gets above freezing during the day (enough to melt the ice in the basin, even if I don't remove the shade cloth) I've been able to keep plants from having any freeze damage at all, down to 25 degrees. Aluminet is what I use in summer to keep my hens cool; the temp under Aluminet (I use 70%) is a good 15 degrees cooler than under black shade cloth. How does it keep hot things cool and cool things warm? I dunno, but it's miracle stuff! I got mine at Farmtek, but it's available elsewhere.

    ReplyDelete
    Replies
    1. Dear Meg,

      Thank you so much for your response! That was a very well thought out and helpful response. How long does the Aluminet last? Also - where do you garden?

      Delete

Dear Gardening Friends,
I look forward to learning more about gardening with you. Your comments help me recognize that gardening is a life-long journey.

To advertisers: Note that this blog is concerned with gardening and gardening techniques. Please do not attempt to advertise here by leaving a comment. Depending upon how egregious the comment is, it may be deleted. I would prefer to have no advertising on this site at all, and am planning on removing all advertising in the future.