Just had another thought. Do kerosene heaters give off anything that would harm plants, if in a greenhouse type structure?

You might want to check out soil heating cables (electric). Green house suppliers have them.

Here is a link that might be useful: Charly's Green House

Hi,

Here's another link re: soil heating cables:

http://loveapplefarm.typepad.com/growbetterveggies/2008/01/soil-heating-ca.html

Anne

If you have just a few plants that you want to put out early, you could do what I did a few years ago. It's kind of ghetto, but it worked. I built a box out of some scrap wood and covered it with ten mil plastic sheeting stapled to the framework. I put two incandescent bulbs inside the box and at night I covered the setup with an old sleeping bag and some ratty wool blankets. When the nights got down to 30 degrees, the temp. inside was 10 degrees warmer. I will say this, though - by late June those plants weren't much larger than the ones I set out a month later, so I don't think it was worth the trouble just to have a few tomatoes ripen a couple of weeks earlier.

Scott in Napa

A couple weeks you say? I guess in such a sublime place as Napa you would have a pretty long growing season. Up here having a couple weeks head start on ripening tomatoes could mean the difference between getting ripe tomatoes or not. Cherry tomatoes are not such a big deal, but some of the larger tomatoes requiring a longer season need every week it can get up here. Some summers the heat and sun wind down earlier than others leaving us with a whole lot of green ones. True you can do the windowsill thing but it just isn't the same somehow.

A lot of people have success with the "Wall-of-Water" plant cloche, the kind you fill up with water. It provides 2-3 weeks headstart, and does help on those frosty nights. They're kind of expensive, though, and you can do the same thing by surrounding the plant with 2 liter pop bottles or half-gallon milk jugs filled with water, then throw some bubble wrap over the top on cold nights.

Setting up a greenhouse would be best. You must have heat and the fumes from the kero unvented I would not recommend.

I start some a good 3 weeks early every year like this and it really pays off. Not only can you heat at night to encourage fruit set, eliminate cat facing, enhance growth etc. but daytime advantages prevail as well.

You would have to come up with a way to not only consistently heat, but cool as well. You can loose your crop from just one cold night or one hot day, take your pick.

If you can get your frame up soon and cover it then the soil will warm. I never worry about soil temperature in my central PA high tunnels by March. In fact the soil never freezes inside my high tunnels except for a few feet along the sides. After a few sunny spring days like today when outside temps never got over 40F but it was 95F inside my unheated tunnels the soil under a plastic canopy is warm enough. Its the air temperature at night (or days as timmy stated) that can kill your plants.

So start you plants and get your frame up and covered as soon as possible. If you sow seed now inside you are setting yourself up for an early April planting date. Though early April isn't suitable to set plants out unprotected, it could allow you to plant under a plastic covered tunnel with a minimal amount of supplemental heat.

The rule-of-thumb for covers is that you gain one zone for every cover used. Last year after planting tomatoes in early March in a tunnel I set up a canopy over those plants within the high tunnel and covered it with Typar. Then I placed a few wire hoops randomly over the plant rows and pulled remay fabric over it. I did use a propane heater and a hanging box fan a few nights between layers but overall the heat expenses were minimal. The covering and uncovering on a daily basis was a hastle.

This year I'll have a double inflated plastic cover on the early planting tunnel. I plan on retreating to previous year's methods of heating with an end-vented wood burner and using the circulation fans to eliminate cold spots.

As timmy mentioned you need to have a cooling plan. Rollup sides are fine for June thru October but for March thru June when you want the structure as tight at nights as possible a thermostatically controlled exhaust fan is a more reliable option.

You mentioned that you were open to electric means. My system thrives on electric to operate the fans and intake louvers. But electricity is too expensive as a heat source for a larger volume of air. If you are thinking about using the inner row cover you might consider stringing decorative lights amoung you plants. That might gain you 6-10F temperature rise where you need it assuming that you can trap much of that heat in the vicinity of your plants.

I've used a low tunnel successfully for several years. I make it from 18" pieces of rebar as stakes, with 10' pieces of 1/2" PVC pipe as ribs. It makes a nice low cover over 4' wide beds, using regular 'ol clear poly. It works great to warm the soil early, and then covered with floating row cover, to provide a nice warm environment for early growth.

Here is a link that might be useful: my hoop house

I have found a good way to get those plants in early. Do not plant them in the ground, instead,plant them in a 5 gallon bucket with the bottem cut out and set into the ground 4 '. Now your plant is above ground and can be warmed by the ambient temperature air flow.

Tip: I found that a hand mixer blade used with a cordless drill, makes an excellent tool for digging a hole and mixing compost into the soil.