Winter heating

Last night was the coldest we’ve had this year, and it tripped my greenhouse temperature alarm. I run about 5000 BTU/h of electric heat in the geodesic greenhouse during the winter. Together with about 2000 BTU/h added to the water tanks, that suffices for most nights and all but the coldest days in our climate. This year I had to strip away the inner plastic lining because it was deteriorating, which has left me with less insulation that normal, so I expect to be using supplemental heating more. Not the most economical way to run it, I’m afraid, but sometimes I don’t have a choice.

I haven’t set up the water heating yet this year, and that is hurting things as well. So last night I fired up the supplemental propane heater. It’s capable of 18,000 BTU/h in three segments, and each segment adds about ~10F differential to the temperature inside the greenhouse versus outside, normally. With less insulation this year I expect it to be less effective, but still hoping it can pull me through our coldest nights. I checked all of the fuel line connections and the venting and fired up each segment for a good, long burn to make sure they burned safely and completely after its long time shutdown since last winter.

Unlike the electric, which is all thermostatically controlled, the supplemental heating is all manual. And that suits me fine. I’m a pessimist when it comes to automated systems. I expect water pumps to clog and cut out, fans to die, and auto shutoff mechanisms to fail. And I don’t trust the propane completely in a location with no one present to monitor it, so I feel better when I have complete control over it. I’d rather forget to handle something and have the greenhouse freeze over, than have it burn down because I wasn’t forced to go out there every time it turned on, off, or fired up another burner.

After the test I walked around inside a bit. The Angel’s Trumpets are still blooming like crazy. Fuschias and some runaway nasturtiums add dashes of bright color here and there. I’ve overwintered the habanero family peppers (heatless, full heat, and ghost chiles) to see how they do through the winter and how they perform in their second year. Everywhere the greenhouse is crammed full of plants, arranged for maximum light exposure while still allowing air circulation and access for watering. It’s a bit of a mess, really, arranged for plants rather than people. And I love it.

Tomato transplanting

tomato seedlings closeupTomatoes germinate for me in 2-10 days, depending on the temperature and freshness of the seed.  It is imperative that they get under lights immediately after they hatch or the stems will quickly become very long.  I use metal halide lamps with a daylight (blue) spectrum, which lets me cover a large area without needing the plants right up against the lamp, and additionally provides heat.  I’ve had better results moving the seedlings outside from metal halide illumination than from flourescent as well.

I usually wait to transplant until I can see the beginning of the second set of leaves.  This generally happens at four weeks from the time of sowing, but really it varies with the variety of tomato and type of leaves as well.  I can get away with this anywhere from 2-6 weeks, after which the seedlings start to deteriorate.

Tomato TransplantsI flood the trays with water about one hour before transplanting which loosens the soil and makes the seedlings easy to pull out.  They are planted in 1801 deep flats and buried as deep as possible without covering the leaves.  I use Promix BX for this, which has given me the best results of anything I’ve tried.  I can hand transplant about one tray every 5 minutes, which still adds up to 12 hours of work for the 72 flats I did this year.

Currently I don’t fertilize, spray or use any chemicals at all on the tomato starts while they’re in the greenhouse.  The inserts and soil are new and reasonably sterile and I’ve never had issues with tomato fungal infections in the six years I’ve been growing large numbers of seedlings at my present location.  I’ve thought about using an organic fertilizer, but really I don’t know what I would want to gain from it.  My plants are strong, vigorous and sturdy at the time they’re ready for sale.

Geodesic Greenhouse

Geodesic dome greenhouseAt some point in the future I’ll probably add more information about it on this website, but for now the construction details on my primary greenhouse are hosted at

It is a 20-22′ (depending how and where you measure it) 3 frequency geodesic dome built with cedar and glazed with heavy duty woven poly plastic. The construction was very rewarding, and after having it for several years I’m sold on the design for greenhouses in our climate. It will show up throughout my future posts.