Richard

I'm considering partially raised beds for the 5 banana mats I will build in the late spring. The beds will be 6" below ground plus 12" above, and about 7' by 4' each. The walls of the bed have a narrow vent every 16" for drainage.

Anyway, I'd like to keep these beds from getting too cold during the winter which is pretty mild here in zone 9+/10-. Has anyone experimented with running heating cables around in an outdoor raised bed?

Thanks ...

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bencelest

I installed heating cables under the soil a couple of years ago at the same place where I am building my raised bed now. I installed it and had my potted plants on top of the heating cables. I let it run for a few nights but I stopped turning them on when I found out that the heating cable was rated at 1800 watts. I figured it is just like turning on an iron or a room heater all night long. I did not want to pay the extra electricity so I left it off all the time and finally I removed it. I still have the heating cable uninstalled.
I figured I am better off using Christmas lights to warm up the soil.

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CookieCows

I'm interested in everyone's raised bed information. I'd like to plant as much as possible in the ground eventually. We live in the rocky/caves area of Kentucky and it's neat... but now that we live here we know that everyone knows what property is lacking topsoil. Ours is one of those. (maybe that's why we got it so cheap?) The details on the making of the raised beds for what bananas like is greatly appreciated! Thanks!

I really liked your photos of how you made the bed for the trees too.

Deb

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CookieCows

I looked up another thread on this to see if you meant something as simple as laying them on the ground and yup that's what you meant! Was wondering if you ever tried it?

Deb

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bencelest

Deb:
The heating cable is suppose to be permanent and out of sight since they were installed under ground. The Christmas lights are temporary since I just wrap them around the pot and around the tree trunks.
One drawback of using Christmas lights:
One of my neighbors asked me one day why I had Christmas lights on in my backyard way past Christmas time. (LOL). I've been using them for 3 years now. But this year, I only use a few CL since my plants are well established now and they can stand on their own.
I am not a pro and I have no experience putting up a raised bed yet but I'll just use my common sense doing it. The main ingredient of a good soil is pH. It should be near neutral 7.0 and slightly acidic and the soil must be well drained and fertile. I am also thinking to spend the least amount of money and not grow hog wild buying things.
So I will get the sand free near the beach once I drained all the salts from it.
Then get me a bulk of redwood bark or something similar, then a bunch of steer manure bags and perhaps, perlite, and I have a lot of compost in my yard and top soil. I will also scout for tree trimmers who cut up the leaves and trunks of the trees they cut. They cut them into small bite size bits. I'll use them as mulch.

Someone comment about my structure I am building and here's my answer:




Joined: 13 Nov 2005
Posts: 1331
Location: Salinas, California

PostPosted: Sun Jan 20, 2008 10:30 am Post subject: Reply with quote Edit/Delete this post
Green: Thanks for the kind words. I am just thinking how I can grow my citrus and bananas the cheapest way possible using nature as my friend.
I'll try not using propane or electricity but using good insulation from the wind. And maybe, maybe install a vent free heater using natural gas as heat source I think the cheapest of them all.


Last edited by bencelest on Sun Jan 20, 2008 10:43 am; edited 2 times in total

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Richard

I am using the C7 type of Christmas lights to provide warmth to a row of Pitayas. The string of lights is about 1 foot off the ground and 1 foot away from the plants. I found that if a light bulb is closer than 8 inches to the plant then damage to the plant occurs. The string of lights is connected to an outdoor thermostat which switches on when the temperature drops below 45 (F). This only occurs at night for a few months in sunny Sandy Eggo. The "string" of lights is composed of two strings, each rated 25 watts, for a total of 50 feet.

As for heating cables in a raised bed, my thought was to embed them in the walls of the planter which would be constructed with some insulating material. The 1800 watt cables bencelest spoke of sound like those used for floor heating in homes when a builder in Southern CA thought electricity would be cheap forever (1960's). I have found heating cables designed for greenhouses that are rated from 100 to 300 watts, depending on length and design. I could afford to run five 100-watt cables for 10 hours per day for 3 months. Has anyone tried this?

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bencelest

Yes it is true that I ordered the heating cable from Ebay and it is designed for floor heating.
Richard , can you tell us more about the greenhouse heating cable ? ie where can you buy them? What brand? etc....
I am also skeptical as to the heat it can generate.
I believe someone posted in another website regarding this a couple years back that it did not give enough heat for the plant. I maybe mistaken though.

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CookieCows

Originally Posted by bencelest That is so funny! Our neighbors can't see us so we could get away with it.

I have a couple questions...The area we're working with for the raised bed can be as wide as we want but I'm thinking of keeping it about 4' wide. Right now it's a mound with junipers that extends about 40 feet that we want to change into a raised bed for tropicals using large rocks for the walls we can get pretty cheap from a quarry. I'm struggling with the soil. Should I try to transform the existing soil which is cheap top soil that was trucked in by dump truck or dig it out and buy new soil in bags and mix up the same composition as for pots. Obviously if I go the route of digging it all out I won't be able to afford the soil mix for the entire length all at once which is ok... we'd just extend as far as we can and then do more next year.

Originally Posted by Richard My next question is what kind of insulating material were you planning to use to build your walls?

The last question is that our bed will be aprox. 24" deep with bedrock at the bottom. Does that make a difference in what we'll be dealing with come winter as far as ground temp.? Does it mean that it might not retain the heat as well? I'm leaving out any thoughts of burying a heating element right now. I don't want to get into all that if we don't have to. I'm only going to put the hardiest tropicals into the ground and the two fruiting banana's I'll leave in pots to bring in the house in winter. Any ideas of the best way to go about this will be greatly appreciated!
Deb

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natedogg1026

There were two main reason I raised my beds. One, drainage. We had 22 inches of rain in one month last year and I lost a lot of plants just simply because the water table was maxed out. Raising the beds six to eight in. will give the roots somewhere to go in order to breath. The beds are surrounded by bricks and mounded up and water should drain through the cracks. I don't think there is any reason to worry about making a special drain. The water will find a way out. Two, they warm up faster. This should help speed the growth of the plants in early spring with warmer soil. Also they will stay warmer in the winter helping to make it easier for my plants to survive. Since I was raising the beds I figured it was also time so start over with my soil. I recycled what I had by mixing it 50/50 with compost and added a little gravel for drainage. As far as the heating cables, sounds a little extreme but I would have said that 2 years ago if I were to see my present Nana collection! --NATE

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Taylor

CookieCows

My husband told me earlier to go out and take a picture of the mound for the before shot and I said, 'no.. there are too many weeds on it!' LOL Guess I better get out there when this freeze lets up!

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Richard

I would dig a hole now (January) down to the bedrock, place an agricultural temperature probe made for this purpose there, and then bury the hole -- with the wires from the probe coming out of course. Now that disturbed dirt in the hole will conduct heat and water more than it did before. Cover it with a piece of plywood and put some rocks or something heavy on it. Record the temperature at 6am, noon, and 6pm under different weather conditions, ALSO recording the outdoor air temperature in that area at the same time. You'd prefer if the bedrock temperature did not drop below 45 (F). If it stays above 55 (F), have a party!



My biggest concern with your plan is drainage. If you are building a PARTIALLY raised bed over bedrock, then you are focusing water over the same. Personally, I would construct one or two french drains to wick excess water out from the deepest portion of the bed.

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Richard

The greenhouse heating cables I've seen are not for heating the greenhouse but for providing more heat at a specific location. The greenhouse itself has its own (typically gas) heater. So I wasn't surprised that someone was disappointed with the performance in an unprotected outdoor situation.

Also, Benceleste and I are in zone 9, so outdoors we are really only fighting a 10 or 15 degree (F) difference between low overnight temperatures and the lowest temperature we want our tropicals exposed to (45 deg F). IF I lived in a colder climate (e.g., where I lived in McKinleyville, CA or in Denver, CO) I would have a greenhouse and grow bananas and other tropicals in tubs on an insulated floor.

I have seen the greenhouse heating cables advertised in catalogs that arrive here every month or so by postal mail. I'll search around in the recycle bin for one.

CookieCows was asking about how I would insulate the walls. So far the cheapest solution (but the most labor intensive) is channeled cinder block stacked 3 high; they measure 6" wide by 8" high by 16" long. I would mortar them together, but fill them with R30 insulation instead of concrete. The heating cable would run down the channels. The bottom bricks would tarred to a 6" wide strip of 1" thick rubber matting that is used in construction. The top of the bricks would also be sealed off. A temperature probe would also be placed internally, but at some distance from the heating cable. I think I would set the cable to come on when the temperature drops below 50 (F).

To find out if the cable is necessary, I am currently building another raised bed but for a non-tropical plant. I am going to construct it without a cable, but with the temperature probe and measure what is going on.

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Richard

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CookieCows

A temp. probe! Why don't the simple solutions come to mind ... LOL I searched online and finally found a reasonable priced one in the $20 range for home use but will go to the feed store to see if they have one first. A french drain is a good idea. I think I have the soil worked out in my mind so I think we're good to go. Will post pics as we go. I love seeing everyones pics and plans!

I just want to pick out plants!! )

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AllenF

I have a heated shelter in use here in Zone 3 that is designed to maintain the air and soil temperatures at or above the freezing mark. It has maintained a short term temperature of -6*C/20*F in weather of -25*C/-15*F with a 30 MPH wind and a windchill of -35*C/-32*F.

Normally it maintains 0*C/32*F at -10*C/12*F and -2*C/28*F at -20*C/-5*F with little or no wind. Sun light can raise that temperature to as much as 12*C/50*F at -20*C/-5*F.

The heat cable turns on at 37*F and off at 43*F. It uses only 2.5 watts per cubic foot of air space.

If anyone is interested, I can post the details or PM the details.

Allen

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Richard

Way to go, Allen!

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bencelest

I am very interested specially the wattage use per cubic foot.
Please PM me or post it here so others can know.And the thermostat you are using.

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Richard

Of course a 12 x 12 x 12 ft greenhouse heated by a 2.5 W / cu.ft. cable would draw about 4300 W. A small butane-powered heater with clothes-dryer ducting and thermostat control would go through a $35 gas canister about once a month.

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bencelest

That would equal to 4.3 Kilowatts per hour.
It is more than I am willing to pay for electricity. So that's out.

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