i would just use row covers if i didn't need to worry about freezing. i think without supplemental light this will be very slow growing basil.

120 watts stretched over 40 feet is not going to make much heat at all. The cable itself might be 72 degrees, but if the ground is cold, that heat will wick away quickly. Soil has a lot of mass, which takes a lot of energy to heat, and that is before the wicking effect of the surrounding cold Earth. If you're paying for electric heat, it might be worthwhile to insulate around the edges of the cold frame. Or you could grow off the ground altogether.

I am most interested in using solar collectors to heat water, and then letting that water provide the overnight heat. It's free energy, which is about all I can afford :)

Good luck with the basil project.

Thanks to both of you,

I saw a video of some guys growing in rain gutters with heat cables inside a high tunnel. Some of you with tunnels might be thinking about that?

In 2011 grew a watermelon outside from a transplant starting in Late January or early February, with the heat cables in front of a south facing wall.The plastic was held just above the leaves. You can see it in my 2011 diary on bigpumpkins.com, if there is any interest. The Carolina Cross plant was a very healthy monster and grew very fast. Feb. is barely warmer here in the day and equal at night with Dec. and Jan. It even snowed once after the watermelon seedling was planted!

As you all know,heat rises, so that helps with loses when the low slung cold frame traps the heat rising from the soil into air. I think it cost about $25 a month to run the 2 sets of 40' direct buried cables, but that should be fact checked.Electricity is probably higher here than almost anywhere else. It couldn't have been much more though because the bills weren't crazy high. I can sell around $300 or more, a month in basil and having it year round could help with the "prestige" issue at the stand.

Passive is better!If it works. Isolating the soil with insulation has to be good either way. Black water bottles added to the cold frame would help. It certainly is easy to try passively outdoors. I am setting some up basil in a south facing window in trade gallon pots and can add light if needed...cheaper than outdoor heat but space is limited unless I put in skylights....Hmmmm!

The other deal is, if 10 hours of daylight works, is just to grow in the trade gallons in manageable totes that I can lift out of the cold frame and bring indoors on cold nights. Sounds like a lot of trouble but the learning curve...and getting something to market this winter may be worth it.

I believe that the cold AIR temps is what kills basil.

I believe that is what kills basil Marla, but I am wondering about how to make it thrive in my mild winter, and soil temps will be a factor too. Do you know what air temps kill it and what soil temps are minimum? Minimum hours of direct sun?

At 50 degrees, Basil will turn black. Under that it will be killed. Don't know about soil temp or # of sunlight hours.

O.K. We will dip under 50F, soon. Figure the basil in the garden will be finished.
I found minimum soil temp to be around 60F and 6 hours of full sun. Our soil drops to at least 50F. I imagine 6 hours of winter sun is not the same as 6 hours of mid-day summer sun but our 10 would probably do.

You can cover the basil with cotton/cloth to help protect it for a few degrees.

so does the 50 degrees kill the whole plant or just damage the leaves?

Once you kill the leaves, the plant can't get what it needs to continue to grow.

Hang on and back up a second. Basil will absolutely not turn black at 50F, I think there must be a typo here from Marla.

My basil is still green and looking great even though the temps have dropped into the 30's.

From my experience, basil will turn black from frost damage, 32F and below.

Mine always started to turn black after dropping below 50, and all the hundreds of books that I have agree with that. You must have a micro-climate where it's warmer. Lucky you.

Marla

No micro-climate here, or any of the farms i've run over the past 17 years. When my thermometer says 41F like it does now, my basil is still green and fine. I can post a picture if you want.
My basil has always stayed just fine till frost. And beyond that with row cover.
Don't know what to say about your books or your experience, just that mine is very different.

The only other thing I can think of is that super tender basil leaves may be more prone to damage than older, tougher ones. I don't replant past July, so my Genovese plants are not so tender anymore. But they taste fine and sell well at the market.

Madroneb, Is it regrowing with any vigor after you cut it, or just kind of holding until you pick it and not growing back? If it's as old and tough as you say it might not grow back after cutting even it best temps?

Do you all feed your basil? I think it takes bad soil, so I never have worried about feeding it after putting it in a composted bed? So far so good, after 8 months. If you feed them what do you use?

I apologize for highjacking the thread, hopefully this is interesting to someone.
Here is a photo of some of my basil this morning after another night of 40F.
Granted, I cut this patch hard last week so it's not pretty, but its also not black at all.

If basil was to blacken at 50F, I couldn't grow it.
In spring, when frost stops around May 1st, I transplant outside while night temps are still way below 50F. Here in NW Oregon, temps stay below that long into early summer and go there again late Sept.

The regrowth is slow, but noticeable. Obviously not like hot summer growth.
I add good aged manure to the bed before planting, and thats it. If I watered with fish emulsion later on, i'm sure it would grow much faster.

No worries about thread jacking, thanks for your comments.
After your first post, I remembered that I put my first basil transplants out under agribon 19 in early March and it got down to around 40 several times. Definitely much lower than 50 under the agribon. It takes a long time to warm up at night here in spring too, not to your extreme, but not too far from it.

Cole Robbie, Just reread you post. I don't set the cables up in a row. you are right that would not work well. They are run back and forth about 4" apart. 40' makes a bed 45-50 square feet. Then the bed is covered with plastic at night and on cloudy days...maybe half open on medium day. That's how I grew the watermelon in winter/early spring. It couldn't hurt to insulate the bed, use black mulch , or build up a insulated box and put that under plastic.

From what has been said so far on this thread, I might be able to grow basil in a sheltered south facing location in a basic cold frame. Maybe put in a hot lamp and add a second blanket on the coolest nights. That has worked with warm season seedlings before. Watermelon, peppers, Tomatoes etc.

The other way I saw the heat cable used was in a rain gutter above ground. The soil mass was small and it was in a greenhouse which helped. Has to be a cut and come again type high value crop.

Anyway, I have the transplants ready to go and am starting another tray to experiment with.

Thanks

I've always planted Italian Large Leaf, not the Genovese type. I realize planting on the other side of the Cascades is supposed to different than the Midwest. We don't have any ocean, or any large lake, to help with the weather.

i have a patch similar in plant size to madroneb's. we've had temps in the 30's, no heavy frost yet. some of the leaves on my basil are black but not all.
the basil that was planted in a hoophouse and in a high tunnel last spring is still going strong now. it has been through some cold periods and had some leaf damage but never enough to kill the whole plant.

Our basil grows well all winter (PHX AZ), unless we have a frost and I forget to cover it. If it were in a hoop house or with row covers I wouldn't have to worry.

It grows more slowly, but I have a lot of basil plants.

The advantage to overwintering them is they explode into growth the next spring. I kept some alive for three summers and they were great.

Thanks lazygardens. I have a few basil stands, but the older ones had a bunch of black fungus on the undersides of the leaves. It comes on very quickly and makes it unsaleable in my opinion. I have learned that it is a seasonal thing. Younger plants look O.K., so I think I'll grow it for cutting whole plants until this problem seems to go away...which will probably be in the spring.

Wierd, I had really nice basil today at the market and my worst sales of it all year. Hope that doesn't mean people don't want it as much in winter.