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General discussion regarding the techniques and methods used to successfully grow tomato plants in containers.

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Old August 20, 2016   #1
schill93
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Default Insulating containers

I live in the VERY hot desert of Las Vegas. I grow in containers which is very difficult here, but my physical limitations force me to do so as I have everything raised as I could not get down to the level of a raised bed.

I have an automatic sprinkler system with emitters in each pot, so that's not a problem. But once the temperatures start climbing into the 100's in June-August, the sun bakes the planters, and I think nearly boils the water in my Earthboxes. I have wrapped the other 15 gal round landscape containers, which I also use , with this stuff, which I think helps.

ttps://www.amazon.com/Reflectix-ST16025-Staple-Insulation-Inch/dp/B000BQSYRO/ref=sr_1_1?ie=UTF8&qid=1471721404&sr=8-1&keywords=Reflectix+insulation

However, it is my understanding that to truly insulate something you should have an air space between the object and the insulation to be most effective.

I've been Goggling for ideas on the internet. One article suggested packing a thick wall of dried leaves around the container using either a pot inside a larger pot or possibly a bag (not sure how you would handle drainage using a bag).

If you used a pot inside a pot, then for proper drainage I think you might need to cut the bottoms of the larger pots off. (I'd hate to do that, but would if it worked)

My plants are in the ideal area (East) getting only sun to about 1 PM. I also mulch the top with about 4" of mulch once the temperatures start to rise. I will also be adding some shade cloth next year come June. But I want to do all I can to cool planters down as well. Luckily, these plants are hidden on the side of the house that no one sees, so aesthetics are not paramount.

Any engineers out there to suggest the best way of insulating the pots and Earthboxes? (Besides moving )
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Old August 20, 2016   #2
dmforcier
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You're not going to prevent heating due to air temperature, but insulation might delay it until the cooler evening starts to drag it back down again.

Solar heating is a bigger danger, especially with dark pots. I'm using black nursery pots. Currently I use white plastic garbage bags both to reflect sunlight and form an air gap. It seems to work pretty well, but I don't have the intense sun here that you do (I'm in partial shade). Last time I had pots in all-day sun I used black drawstring trash sacks and snugged up the drawstring to keep the bags up. The heavy bags blouse out to give a larger air gap. Worked well.

A consideration is water. My big plants in the big pots would drink a couple of gallons a day, and the cool water - input all at once - probably cooled the pots some. (Just cut a hole in the bottom of the bag to let excess water out.) With an automatic system, is your water heating before it gets to the pot?

Now, a bit of theory on insulation. The best insulation is a vacuum. Obviously we can't do that. So let's look at how heat is transmitted from one place to another: radiation, conduction, convection. Direct radiation is blocked by an opaque shield, but can heat the shield, transferring energy by another means. A simple air gap is very effective in preventing transfer through conduction, but it allows convection. Foam insulation (or leaves) allows (usually) a higher level of conduction but prevents convection. Theoretically, the better solution would be an opaque shield back by an air gap with vents top and bottom to permit the air heated by the shield to rise out of the gap.

Or buy a bunch of tiny little air conditioners.
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Old August 21, 2016   #3
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Quote:
Originally Posted by dmforcier View Post
You're not going to prevent heating due to air temperature, but insulation might delay it until the cooler evening starts to drag it back down again.

Solar heating is a bigger danger, especially with dark pots. I'm using black nursery pots. Currently I use white plastic garbage bags both to reflect sunlight and form an air gap. It seems to work pretty well, but I don't have the intense sun here that you do (I'm in partial shade). Last time I had pots in all-day sun I used black drawstring trash sacks and snugged up the drawstring to keep the bags up. The heavy bags blouse out to give a larger air gap. Worked well.

A consideration is water. My big plants in the big pots would drink a couple of gallons a day, and the cool water - input all at once - probably cooled the pots some. (Just cut a hole in the bottom of the bag to let excess water out.) With an automatic system, is your water heating before it gets to the pot?

Now, a bit of theory on insulation. The best insulation is a vacuum. Obviously we can't do that. So let's look at how heat is transmitted from one place to another: radiation, conduction, convection. Direct radiation is blocked by an opaque shield, but can heat the shield, transferring energy by another means. A simple air gap is very effective in preventing transfer through conduction, but it allows convection. Foam insulation (or leaves) allows (usually) a higher level of conduction but prevents convection. Theoretically, the better solution would be an opaque shield back by an air gap with vents top and bottom to permit the air heated by the shield to rise out of the gap.

Or buy a bunch of tiny little air conditioners.
Thank you for your feedback. I can't say I understand 100% the conduction/convection, but it appears I was right about having an air space would be helpful.

Concerning water, my Earthboxes did not fare as well as my containers, which is not the norm usually. But I am attributing that to what you said in that I think the top watering actually helps cool the plants somewhat, while the water sitting on the bottom of the Earthboxes just gets too hot here and the plant roots are getting mostly hot water. Also the depth of the Earthbox is shallower (only 12" deep by 30" wide), which I don't think bodes well for this type of climate. I don't know for certain, but it sounds reasonable.

I realize I'm fighting nature here.

Last edited by schill93; August 21, 2016 at 08:45 PM.
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Old August 21, 2016   #4
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Convection is at its root conduction that uses an intermediary -- in this case hot air -- to move heat from the hot place to the cool place. If you have hot air, just give it a place to go before it heats up the inner mass.
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Old August 22, 2016   #5
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Styrofoam, like the one in packaging, is used around here to insulate buildings, so I assume it should help in your case too (wrapped after in the reflective thing). I think the problem is how well can you add it all around. If one side (up) remains without, I think the effect will not be that great.
Shade cloth will help more than you think.
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Old August 22, 2016   #6
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Here is a link from a past thread with pictures of different containers I have used. you can see plastic containers I used on the fence line and some dark blue ones I wrapped styrofoam around so they would not heat up. Also in the modified green house which I'm growing my tomato plants in Styrofoam ice chests. They keep the root zone temperature stable and will last about 2-3 seasons and are inexpensive. I used an apple corer to make drain holes, one at each end 2 inches up from the bottom of the cooler leaving a small reservoir so the aggregate won't dry out like a SWC.

Ami

http://www.tomatoville.com/showthrea...ight=Styrofoam
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Old August 22, 2016   #7
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Quote:
Originally Posted by zipcode View Post
Styrofoam, like the one in packaging, is used around here to insulate buildings, so I assume it should help in your case too (wrapped after in the reflective thing). I think the problem is how well can you add it all around. If one side (up) remains without, I think the effect will not be that great.
Shade cloth will help more than you think.
Zipcode: What do you mean "If one side (up) remains without, I think the effect will not be that great>" Are you referring to the top of the container? If you are, I considered that too. If you have an ice chest and leave the top off everything is going to melt much faster from the exposed warm air getting in.

There still is no air space between your pot from either the Reflectix or insulated styrofoam and that would be optimal if I could figure how to do it.


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Originally Posted by amideutch View Post
Here is a link from a past thread with pictures of different containers I have used. you can see plastic containers I used on the fence line and some dark blue ones I wrapped styrofoam around so they would not heat up. Also in the modified green house which I'm growing my tomato plants in Styrofoam ice chests. They keep the root zone temperature stable and will last about 2-3 seasons and are inexpensive. I used an apple corer to make drain holes, one at each end 2 inches up from the bottom of the cooler leaving a small reservoir so the aggregate won't dry out like a SWC.

Ami

http://www.tomatoville.com/showthrea...ight=Styrofoam
Amideutch: I have often considered the styrofoam containers. Every time I pass them by, I notice them, but think they look too small. I would gladly buy some larger ones if I could find some. Could you tell a difference when you wrapped the styrofoam around your pots? Had you had them exposed without it before?


Also, for the Earthboxes, I have considered buying 4 x 8 2" slabs of insulated styrofoam from Home Depot, and cutting 4 sides to fit around boxes. It would be expensive, and time consuming for ten boxes.

I also don't think that plastic cap used on Earthboxes works that effectively here. I was considering buying some type of flexible material like 4" vertical blind and wrapping it around inside the box to give me more height and then put 4" of mulch on top instead of the cap. (and extend the water fill tube.)

Actually thinking about it, I might be able to use the Reflectix and cut it in half to 8" to stick in there to give it more height for the mulch.

Maybe I could buy a commercial ice maker to install next to my garden, and every day fill up my Earthbox reservoirs with ice cubes!
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Old August 22, 2016   #8
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The biggest difference you can make is simply to shade your containers from the sun.

You aren't going to be able to counteract the air temps without the tiny air conditioners. Remember that fixed insulation like foam will also hold heat in, preventing the soil mass from cooling at night.
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Old August 22, 2016   #9
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Originally Posted by dmforcier View Post
The biggest difference you can make is simply to shade your containers from the sun.

You aren't going to be able to counteract the air temps without the tiny air conditioners. Remember that fixed insulation like foam will also hold heat in, preventing the soil mass from cooling at night.
"Tiny air conditioners" in my back yard ??????
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Old August 23, 2016   #10
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Hey, how dedicated are you?
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Old August 23, 2016   #11
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Quote:
Amideutch: I have often considered the styrofoam containers. Every time I pass them by, I notice them, but think they look too small. I would gladly buy some larger ones if I could find some. Could you tell a difference when you wrapped the styrofoam around your pots? Had you had them exposed without it before?
I never had any problems growing Indeterminate tomato varieties in 26 Quart Styrofoam Ice chests as you can see by my pictures. Plants can be supported by using the "Florida Weave technique" or suspending a over head cable above the plants and running twine down to the base of the plants attaching tomato clips to support.

As far as the insulation holding in the heat, every time you water the plant the aggregate will be cooled as it percolates down through the aggregate aerating it as well.

The foam sheeting I used I found in a store that sells laminate wood flooring and is put on the floor prior to putting the laminate down and comes in rolls. I used double sided carpet tape to attach to the container. And yes it did cut down the heat gain compared to a pot without the foam.

As Styrofoam Ice Chests are inexpensive go ahead and buy one and give it a test. Get yourself a soil thermometer and after planting a tomato in your favorite aggregate monitor the aggregate temperature during the day and see what you come up with.

Ami

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Old August 23, 2016   #12
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Quote:
Originally Posted by dmforcier View Post
Hey, how dedicated are you?
I have a feeling I'm not dedicated enough, but I'm intrigued by your question. I got to see this.

Quote:
Originally Posted by amideutch View Post
I never had any problems growing Indeterminate tomato varieties in 26 Quart Styrofoam Ice chests as you can see by my pictures. Plants can be supported by using the "Florida Weave technique" or suspending a over head cable above the plants and running twine down to the base of the plants attaching tomato clips to support.

As far as the insulation holding in the heat, every time you water the plant the aggregate will be cooled as it percolates down through the aggregate aerating it as well.

The foam sheeting I used I found in a store that sells laminate wood flooring and is put on the floor prior to putting the laminate down and comes in rolls. I used double sided carpet tape to attach to the container. And yes it did cut down the heat gain compared to a pot without the foam.

As Styrofoam Ice Chests are inexpensive go ahead and buy one and give it a test. Get yourself a soil thermometer and after planting a tomato in your favorite aggregate monitor the aggregate temperature during the day and see what you come up with.

Ami

Ami
A 26 Quart would be a little over 6 gallons. The ones I see in Walmart don't look that big but I never checked to see if they stated their size on them (Just eye balling them) Need to look elsewhere perhaps.

Funny you mention the laminate flooring underlay material. I was eyeing that about a month ago while at either Lowes or Home Depot. It's always on my mind I guess.

Yes, I bought a soil thermometer and tried it in both my 15 gal round top watered
containers (that are wrapped with the silver insulation) and then in my Earthboxes.
The Earthboxes were about 2 degrees higher in temperature. It showed soil at about 83 degrees vs round planters at 81 degrees.
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Old August 23, 2016   #13
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Is that typical? Low 80s is not a bad temp. Where you will see root damage is up against the pot wall with the sun shining on it. Can you get a reading there?


It was a joke, son.
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Old August 23, 2016   #14
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Is that typical? Low 80s is not a bad temp. Where you will see root damage is up against the pot wall with the sun shining on it. Can you get a reading there?


It was a joke, son.
Well, I just got the soil thermometer this week and took the temperatures two days ago about 10 AM.' However, the temperatures dropped this week to about 101-102 in the afternoon, and the nineties when I took the temperature.. So it's cooler now. Down from 108-113. I didn't place it right next to the pot, but I see your point, so I will do that.

The other thing was the water timer had just come on about ten minutes before I did it, so that would have cooled down the top watered pot soil.

I assumed you were joking the first time you mentioned the mini AC's. But when you said it again, gulable me questioned myself.. Cute.
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Old August 24, 2016   #15
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I've never had a problem of overheating in my place, so I have never tested the following suggestion.
Why not wrap the container with old towels etc kept wet by an installation giving water drop by drop Evaporation might keep the container cooler. It works fine in homes without air conditioning, a fan blowing on a wet towel is quite efficient.
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