cheap bottom heat!

mycarbumps(Zone 6b E.TN)February 19, 2003

i was looking for a cheap alternative to buying a heat pad on which to start seeds. at $30+ a piece for even the small ones i decided to find a way to build my own heat supply for starting seeds and rooting cuttings. i decided that a 60w lightbulb produces more than enough heat to start seeds that i would use a lightbulb as a heating element. (if it works for lava lamps it'll work for me too!) so i made a run to "Big Lots" and bought a "work lamp" (one of those lights with a plastic cage around it what you use when your working under the hood of your car) and i bought 2 aluminum foil baking pans total cost for everything - less than $6.00 - so i took the 2 baking pans and put them together up-side-down and taped them so they have a hinge like a clamshell. i cut a notch in the side for the wire to run for the light. i put the light (cage and all) in between the two pans and duct taped them closed with the light inside. make sure to seal the hole where the wire run to keep the heat in. i put the light on a timer, right now, 60w bulb runing 30 min. on, 15 min off. all day and all night. i used ice cube trays with holes burned in the bottom with a hot nail to start the tiny seeds in. they just set on top. i wil add newspaper layers or re-adjust th timing if it gets too hot. but hey, its better then nothing and it was almost free compared with a comertial heatpad! let me know what you think... thanks ~Ryan

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shirley52(z 5-6 ks)

I use electric blankets on low.I'm cold natured and my kids think I need one for every xmas.They work good for me.

    Bookmark   March 3, 2003 at 3:58PM
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oldherb(z8 Oregon)

I use a water bed heat matt we found at the thrift store...$2.00 and it works great! Had to play with it a bit to get the temp where I wanted.

    Bookmark   March 5, 2003 at 11:41AM
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pdsyme(z3 N. Ont.)

Be careful with the light between the pie plates. Those light fixtures are not designed to take that kind of heat build-up and will break down in fairly short (think electrical) order. While a light as a heat source is a good idea a little more care for electrical safety is in order. Try a ceramic light socket and high heat electrical cord, possibly something with a silicone or fiberglass inulative layer.


    Bookmark   March 5, 2003 at 9:43PM
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tigerb8(z8 Mississippi)

I use a thermostaticaly controlled 150w spot light inside a 2'x3' plastic tent to start my seeds, the timer would work if your seeds were in a constant tempature and you were able to monitor the temps. I start my seed in a green house which can eaisly get over 100 degrees in the spring on a sunny day, thats why I use the thermostat. I beleive the seeds start breaking down around 120 degrees.

    Bookmark   March 6, 2003 at 10:27PM
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mister_al(zone 7)

I germinate, and grow, my seeds in a 4.5'x3'x2' grow box using a 4' florescent fixture and a 60 watt light bulb. I keep the bulb close to the top of the box (it's used for heat anyway), while the florescent light is kept a few inches above the plants for growth. The temp inside stays at 75-85 degrees, and the whole setup cost me around $20.

    Bookmark   March 15, 2003 at 2:59AM
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BarbC(8 coastal SC)

And I use an old aquarium w/ hood and light - keeps temps at about 76 - 80º and maintains good humidity. When it comes time to acclimate the seedlingsm, just prop the hood open a little at a time.

    Bookmark   March 16, 2003 at 10:43PM
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The aquarium idea I do but alittle differet.I use a hunderd gallon aquarium.I holds 3 flats.I put 6 inches of water in it.Put a submirsable heater in it at 80 degrees.I have a platform I built which holds the flats 2 inches above the water and a light hold on top. My seeds come up super quick.

    Bookmark   June 16, 2003 at 8:19AM
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calpat(zone9ab No.Ca.)

I'm so glad to read this post and all the inventative ways to get what we need without it costing an arm & leg. People use to make great fun of me when I used DH's saber saw to cut up the turkey carcass.Yeh, yeh, I know that's not what Black & Decker had in mind, but it worked just great. Congrats to all of you for improvising!!

    Bookmark   June 16, 2003 at 10:26PM
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I start all of my seeds in 12 ounce plastic mushroom containers and cover them with a matching clear container. These all go on the bed, which has an electric mattress pad on it, during the day. Once I get the first batch of seeds growing like this, they go under a flourescent light. The light I have is a 2 X 4 foot surface mount fixture which is about 4 inches high. This is set up on a stand over the seedlings. Since this fixture has a flat surface, I am able to set my next set of mushroom containers on it and the heat from the ballast and tubes will provide heat for getting this next batch going. The steel case of the fixture is not a very good material for spreading the heat evenly under the containers, so I set a 1/16 inch sheet of aluminum on the fixture to even out the heat for the seeds. This will also prevent any water that gets spilled or passes through the containers from entering the fixture and causing damage.

    Bookmark   July 10, 2003 at 11:02PM
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Has anyone experimented with old waterbed tubes, from somma type mattresses? I have several and a Minipro 8 x 10 greenhouse and live in Maine. Thinking about some passive solar type of heat to stretch the season...My tubes are a dark bluish color, unfortunately not black, but are in good shape . Suggestions??

    Bookmark   July 24, 2006 at 12:35PM
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I start my heat loving plants like Tomatoes, Peppers, Melons in those mini windowsill greenhouses with a see through top I put these in my electric oven and turn the oven light on, and place a thermometer in oven and prop open oven door so teperature stays at aprox. 80F. I put a 6 inch tile against the light as it gets hot at that end. I keep watch as plants like melons reach for light and get to long,Larmil

    Bookmark   September 2, 2006 at 5:00PM
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sandy0225(z5 Indiana)

I have a bunn coffeemaker and I've found that if I set a flat with a propagation dome on top of it, I can start most seeds pretty fast. As soon as they come up I have to find a better lighted location. I guess I need to put my coffeemaker in the windowsill!

    Bookmark   December 18, 2006 at 5:10PM
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albert_135(Sunset 2 or 3)

I am setting as I type with a heatpad on my back that I got at a thriftshop for less than a dollar. There are a wide variety of these things sold and most wind up in the dump somewhere. I have used them for bottom heat when starting seed or rooting cuttings. I used a cheap candy(?) thermometer that I stick in the soil to judge the temperature. They almost never get too hot otherwise you could not put them on your back or butt.

    Bookmark   December 19, 2006 at 2:06PM
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I googled using Christmas lights as a heat source. People here have done it. Yesterday I had a string plugged in while being wrapped around the plastic rack they came on. My thermometer stuck in the middle read 90.2 degrees. That sounds perfect to me. I tried it somewhat similar . The seeds can go on a just above the lights. I guess I could wrap more or less around the rack to get more or less heat. The heat is evenly distributed too, since it is a series of small bulbs evenly distributed over any shape area you choose. Since they are indoor/outdoor lights, they can take a little dampness without fear of electrocution. Also, since we trust them wrapped around a dead and drying tree in our living room, the fear of fire should not be too great. Although wrapping them can concentrate their heat, I think 100ish degrees should not cause a meltdown. 44 watts for this specific string sounds reasonable.

My pepper seeds are on top of the refrigerator right now at 72-74 degrees. The temp is very consistent, but a little low. The ones I have in damp paper towels in zip lock bags have already after just five days. I have not seen any of the ones in seed starting mix come up yet. A bit soon I know. I started these pepper seeds about a month early just so I can practice my method. IÂm a novice seed starter. That is why I am so interested in a heat source other than an expensive heat mat. It seems that if they are too slow to come up, I can use just enough Christmas lights to get the extra 5-15 degrees I need to get them to sprout well. The unneeded part of the string can just hang out of the way.

Can anyone else tell of their experiences with using Christmas lights as a heat source?


    Bookmark   December 28, 2006 at 10:38PM
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nardbarn1(USDA 7 NC)

I utilize the heat from my freezer by placing seed trays on the top. Very nice even heat. Seeds sprouted in 6 days. A neat idea is to use a cat litter pan lined with a pile carpet scrap as a holder for seed starting containers. i like the clear plastic containers from berries , grape tomatoes, mushrooms, etc - the holes at the bottom allow water from the carpet allows water to enter the growing medium. Small plastic pots with holes in the bottoms are good also. By placing the bottom of an appropriate sized clear plastic storage container you have an economical mini green house. I also suspended shop lights from the ceiling as a light source using screw hooks and small link chain (check dog chains in your hardware store - the chain was cheaper than buying it by the foot!). I attached the chain to the shop lights with small angle braces and used coathanger wire to make adjustment easy. Hope this information is useful. Bill in NC

    Bookmark   February 17, 2007 at 10:58AM
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I am using a food warming tray I bought from a thrift store, They use to be very popular but not used much anymore, They produce between 100 and 250 watts of heat.


    Bookmark   February 25, 2007 at 6:16PM
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Last year I used the top of my DH's old(boxy type)computer monitor for my pepper plants. I set a wood block on the back edge to make a level surface for a tray. Then I set my seed starting container(aluminum cake pan with clear plastic lid from the dollar store)on the tray. It stayed at 86 degrees and worked great.

    Bookmark   March 2, 2007 at 11:45AM
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lorax_00(z6 IN)

For the last 5 years I have germinated my heirloom tomato seeds by setting them on my hot water heater. After germination, I place all my seedlings in my unheated (though insulated) garage. In April my garage can be in the 40's and low 50's. All my seedling trays sit on top of a spread out wad of 100bulb white christmas lights. I've had success every year. Tomatoes can handle cooler temps. My peppers and melons have to stay in the house a bit longer, sitting on a 50 bulb wad. Just about the cheapest and safest way to heat your trays.


    Bookmark   March 5, 2007 at 12:59PM
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I just build this light frame today. I used garden bricks. Put two tables together in the basement. Made a flowerbed with the bricks on top of table. Height of frame is 2 bricks. Took 4 pieces of wood the length of the frame and stapled a string of the bigger xmas ligths on each piece of wood. Put those in the frame. Covered the whole thing with old storm windows. Put my plants on the glass and put fluorescent lamp above. In 2 spots on the long ends and 1 spot on the shorter ends I removed 1 brick from the top row to create an opening so there is not too much heat build up.I tried the tiny xmas light on those nets that you can throw over your hedge, but I could not get a high enough temp.Hope I did not put too many lights.

    Bookmark   March 12, 2007 at 11:54PM
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Probably 30 years ago, I read in the J L Hudson seed catalog about a heat box (cardboard!) that uses a light bulb to provide bottom heat for seed germination. Hey, I thought. If a lightbulb can generate enough heat to keep a car battery from dying here in the north, it should work. Ever since, cheapskate that I am, I have been using one. Sixty watt is too hot for my set-up. I experimented and use a small 15 watt nightlight bulb. Works like a charm.

    Bookmark   November 13, 2007 at 7:51PM
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OH!! this is the perfect answer! I too start my seed on top of my big old monitor. I love the berry containers for starting my seed - fill almost full with Pro Mix tamp down, place seed, water well and let drain well out the little slots. I snap the lids shut on the tag (you can also write on the lids - but I reuse them)and I can place 5 containers at a time up there. covered with a tea towel I measured 100 degrees with my candy therm. seed will sprout within a week, and when they touch the lids I pop them open.

I needed bottom heat for my seedlings - I live in a Very cool house - read that as drafty. so I dragged out my old electric blanket - laid down a plastic shower curtain folded the blanket on it and pulled the other half of the shower curtain over the top. had it plugged in all day and could not get any warmth... maybe that is why I still had it in the closet! LOL

I yanked out the string of white light rope I had. within 5 minutes I had heat! how perfect is this?!?! - lights within a plastic tube! I strung it back n forth like the heat tube on a pro bench and placed my trays on top. Using the candy therm ... I had about 85 degrees!
tomorrow I am going to the cheap stores ... in search of !
some more white rope lite!
thanks for a wonderful web site!
best growing!

    Bookmark   January 21, 2008 at 9:27PM
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token28001(zone7b NC)

Been doing some research on cheap, large bottom heat alternatives.

I like this one. I plan to build an 8' long bench filled 3" deep with the rope light buried in the sand. I can set my containers on top of the sand. If I use containers that have no holes, I should be safe. Still, going to put them in the shed to test it this winter. Going to try hardwood cuttings too.

Here is a link that might be useful: rope light bottom heat

    Bookmark   September 11, 2008 at 5:15PM
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I use the christmas lights, too. I have a Rubbermaid under-the-bed storage container that I filled to about 2 inches with kitty litter (not the clumping kind, just the old-fashioned clay stuff). I bury my light strand in that and place my seed flats on top. I can use the lid to monitor moisture; closing it if things are drying out quickly or putting it on just a little cock-eyed to let more air in. My container has wheels on the bottom, so I can easily roll it into or out of sunny areas in my home.

When I'm through growing, I rinse the lights and container with the hose and bag up the litter for next year. Put my shoes back in the container and the house is normal again!

Diana Lynn

PS - If you have a cat, just be sure to close the door to the room your set-up is in. He/she WILL use it!

    Bookmark   September 25, 2008 at 5:52AM
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I just put mine on top of the fridge.

    Bookmark   October 24, 2008 at 8:24AM
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sfallen2002(z5 IA)

Radiant floor.. I can't believe it didn't occur to me before.
Got a pot of squash, peppers, melons on it right now - I expect to have seedlings before next week.

    Bookmark   March 24, 2010 at 9:59PM
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I have used an aquarium heater as well. I bought an old laundry sink that is made of really thick plastic and I put a stainless steel box inside of it. I filled the box with lava rocks that you use for grilling and then filled it with water. I purchased a 15 dollar water heater for a fish tank and put it into the box. I sit my planting trays directly on top of the box which stays about 82 degrees in the winter time. My sink is enclosed in a cabinet with a flourescent light fixture over the seedlings and I have been successfully growing tomatoes from seed for my garden for the last 5 years.

    Bookmark   May 19, 2010 at 12:28PM
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can I use a regular heating pad (for sore muscles) to germinate my seeds using the paper towel/plastic bag method? I put the plastic bags on the heating pad on the lowest setting (warm) and covered with a dish towel. Is this crazy? Is it okay to put more then one paper towel in a plastic bag?

    Bookmark   May 30, 2010 at 12:07AM
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