yeah, too cold to move things from the house to the greenhouse. pots of established annuals got hardened off to the cold weather slowly, so will survive at 45deg, but tender new plants will get quite a shock. I don't move anything new into the GH until it'll be over 55F (that is at the LOW end). Mostly what I do is start seeds in a propagation tent inside the greenhouse, so I only have to heat a small area. cuttings and tropicals go in there. seeds that need cooler tempts to germinate either get started first in the prop tent, or started later (late feb/march) outside the tent. By late feb the prop tent is kept pretty warm--warm enough for stuff like impatiens, tomatoes, or cuttings. If you are starting things inside your house, you will still need to harden off for sunlight, as well as temps. (I started doing the propagation tent because the first year of hauling flats in and out for a few weeks while hardening off was a pain in the butt).

As far as daytime temps: I set a minimum temperature I don't want it to go below, which counts for night and cloudy days. I don't heat higher using heaters just because it's day. The sun mostly makes it hotter in there during the day. I set a max temp so it doesn't get TOO hot (auto vent).

I think low 40s is too cold for cuttings. You might be able to make a go of it if you use a heat mat...maybe...

Friends of ours with a large commercial GH operation start seeds the first week of February but instead of heating the entire huge GH to germinating temps, they crank up the GH heaters only enough to get the space to about 40 deg. and do the germinating under row covers over permanent raised beds with heating coils in them. With our weather, you wouldn't think it would work, but it does.

So perhaps some of those little pop-up hot caps with heat mats might be the answer for someone who can't heat the entire GH to germination temps. but could otherwise keep it in the 40's.

OR: Does anyone else here recall the poster who gave us photos of his clear plastic storage container germinating boxes? Little mini-GH's inside a walk-in GH. I don't believe he was heating the boxes but it would be easy enough to do with waterproof heat mats.

yeah, it's the soil temp and moisture that is most important when rooting cuttings and starting seeds. I should have mentioned that, but was thinking more about the shock of tender plants being moved from house temperatures to 45F.

I should also point out that I use the propagation tent because of space and cost limitations. I can dismantle it and use that space for growing on instead of a propagation area with heat coils, and I can't afford the number of mats I really need. Efficiency wise, heating soil is a lot better of an idea than heating air. Air temp needs to be about 5 degrees higher than you want your soil temperature to be. But I still like having the prop tent because of the humidity and because I can stick other stuff in there (amaryllis really take off).

rachel, that's an awesome idea using a prop tent..I'm gonna try that :)

knotz

thanks to all who responed to my questtion. I like the idea of a prop tent also. I could also crank the heat up in there,just didn't know how high. The temp usually goes up pretty good in daytime except last couple of weeks we've had an inversion so no sun light and temps outside in the low 20's. I'm also starting some seeds earlier this year. My seed starting area is limited so was hoping to move them out sooner. Had trouble last year with plants taking off really slow, so thats why I was wondering about temp. and from what I've read here I had mine way to low.
Rachel how did you make your prop tent? My benches in GH are pretty open for water drainage.

I'll take the plants I started inside and move them out to the GH in March. I have a thermostat that I set at 45 and will put the shade cloth to help with sun.

Here is a link that might be useful: gardening by the seat of my pants

Heya -- I'm also in Idaho.

I heat half of the planting beds in my greenhouse using heating wire (that I've woven through plastic mesh--buried about 3-6 inches below the surface) and then I can run the gas furnace at a much lower setting. The heating wire was super cheap and the electricity cost to run it isn't too expensive either (I looked for a low wattage and no more length than was absolutely necessary.)

You could also use heating mats--I have 3 heating mats in my seed starting area.

I can easily keep tomatoes, peppers, citrus, cardamom, etc., through winter without cranking the furnace. Unfortunately, I haven't found a solution to fix the low light conditions (well, other than expensive lighting.)

Celestial,What kind of heating wire did you get and where did you get it? I have a 2'x5' section under one of my benches that I can grow veggies in like lettuce,radishs, and spinache in. Do you grow your tomatoes and peppers in pots or in the ground in your GH? I love the idea of using my GH all winter, just have to learn what temps I need to have to grow differant things. I live about 30miles N of Boise

> Rachel how did you make your prop tent?

Oh no, I knew you were going to ask. :) It is so cheap that it's embarassing. but it works. I have an old patio table that the glass broke out that I put on top of some pallets (It's about the size and shape of aluminum greenhouse tables anyway, just with less center support); I draped greenhouse film over the table and tucked the ends under the pallets. A small, ceramic heater with a built-in thermostat goes inside. I fold back one side during really sunny days so the heat doesn't build up. By late march I put burlap or a light shade cloth over the top, if I haven't already put the shade cloth over the whole GH (I'm at the 38th parallel, and typically need the shade cloth on the GH mid-late March to keep it from getting too hot). When I don't need that space for propagation anymore, the film gets folded away, pallets get put on top of the table, and it's used for growing on space.

Ultimately I'd like something like this: Starter GH, as a nicer-looking and bigger version. There are smaller versions of this available all over the place, often called 'patio greenhouses' but I'm not sure there's space for a heater. Those would be ideal for use with heat mats though.

Rachel, thank you so much for the info and you are so right so simple and cheap(that part I really like, I'm retired on fixed income.) I have one of those starter gh's with the top taken off, could use that. Wondered why I saved it,now I know, will work perfect. Thanks again
Celestial, googled a search for wire and found some on E-bay. Thanks to you also for your info, Now to go to work

I hold over rooted cuttings of pentas and porterweed for my butterfly garden, and strobilanthes, alternanthera and a few other tender perennials.

My experience is that they must be rooted before cold weather, then they grow slowly if at all in a not-very-warm GH until warm weather. Cuttings that are not rooted but look green, just rot when the weather gets cold.

Nell

Most of your standard annuals thrive in warm temperatures and are usually grown on to finish size at 60-70ºF. Once a plant has gotten established, running the greenhouse cool, like at 45ºF, is a method frequently used by professionals to slow down the plant's growth if necessary. Of course, this might hurt more tropical plants or heat loving plants.

Interestingly, a study done in the 1980's found that plant stretching can be reduced significantly by running the greenhouse temperature 10ºF higher at night than during the day. In other words, they found that running daytime temps higher than nighttime temps caused the plants to stretch. I typically run my greenhouses at about 60ºF day and night once I begin propagation, just to try to save some money on heating. I keep the greenhouses at 40ºF or so when just holding plants -provided there aren't any cold sensitive varieties in there.

It would be nice to afford higher nightime temps but in this economy that scenario just won't fly. I keep in mind that there are many nights in late March and April where not much heat is needed to maintain 50F. For those exceptions do what you can to keep established plants from freezing. Any cover placed above the plants may keep the air around the plants warmer, but more importantly, it will keep the actual plant temperature (always cooler than air temp) warmer.

Go to Tractor Supply or any fencing dealer and buy a few high tensil tentioners, a few long 1/4" bolts to attach to sides and some of the wire to stretch accross the Gh to support the cover you choose. Just make sure that you don't cook the plants during the daytime.