Sunnier means more photosynthesis, which means plant is producing more energy, which results in more growth? That would be my first guess, not soil temperature. Unless the plant doesn't have any green parts on it (so it can't photosynthesize).

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Alan.
My blog: It's not work, it's gardening!

I just bought this greenhouse(12X7X7) for 96.98 including shipping which is transparent poly material and I'm hoping this will be able to hold in heat on winter nights which it should if its air tight. I'm going to have to look around to find a 50gallon steel drum so I can use it to fill up with water and keep it in my greenhouse which will hopefully provide enough heat, with the aid of 20 solar lights and a thermometer to make sure my plants don't freeze.
I'm pretty sure that will definitely make at least a 5 degree difference if its a 5F night outside with strong winds, even more factoring in wind protection.

Heres the greenhouse http://cgi.ebay.com/12x7x7-Large-Greenh ... 3|294%3A50

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well, I think you can really not worry about that one being air tight...

It will work great for keeping the wind off, but I think even with a heater plugged in, you would have an interesting time keeping that one 5degrees above ambient temperature in the winter.

Steve, your plan may work fine but it sounds like lots of effort and giving up space for the barrel. I have been able to get my 20x24x12 hoop house above freezing when temps were sub-zero by running a $40 tiny space heater (on HIGH all night) I've since upgraded but that did work when I needed it. It may be enough for your ghouse, - if yours is single layer plastic though the job may be harder, mine is double layer with air blowing in between and I think that helps alot. Still I bet a small heater would do very well, run it only when it is below 20F or so or whatever it takes to keep the pots from freezing more than a thin layer on top.

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Brad Salmon, zone 5b/6 Southern Indiana
Winters -20 to -25C. Summers 30 to 35C , humid. 115 cm annual precipitation, frost free from May through early October. 259.3 meters elevation. Growing 150+ species. http://www.needmorebamboo.com/

Some other factors are how much temperature increase the greenhouse itself provides, the cold tolerance of moso seedlings with their pots dug into the soil and the duration of time under freezing temperatures. I think 10F and above would be the safe zone and there are only about 10-15 nights it drops below that on average so only the slightest amount of insulation(5F) is all I need, and I want to use a safer source since I'm afraid a portable heater could malfunction.

If temperatures do heat up by 30degrees inside my greenhouse just like yours, I should be well in the safe zone with the steel water barrel since it takes a few days of freezing temperatures to freeze that amount, but I'll be posting pictures of the whole project once I start probably in late December.

I already have a bunch of solar lights, dont know how much they help, 2 gallons of wilt-pruf, clear plastic and a lot of innovation because I'm not going to let any of my plants die.

So Brad, do you keep the pots buried or just sitting in the greenhouse? Do you water them too during winter?

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Pots just sitting on the ground, I think I watered twice, maybe 3x from late Nov-early Mar when I pulled them all out.

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Brad Salmon, zone 5b/6 Southern Indiana
Winters -20 to -25C. Summers 30 to 35C , humid. 115 cm annual precipitation, frost free from May through early October. 259.3 meters elevation. Growing 150+ species. http://www.needmorebamboo.com/

What I learned in my ornamental horticulture courses in college was that the 2 dominant factors in controlling growth in plants are: heat and water. You can have all the sun you want, but if the temps are too low or there is not enough water, nothing will happen. I find that some of my bamboos will burn in winter if they get too much sun at too low a temperature. Blacks in particular.

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Is it soil temperature that causes more growth of shoots and leaves (as Steve mentioned), or air temperature? It seems to me that soil temps at rhizome depth for the most part don't change quickly enough to account for daily fluctuations in the amount of shoot/leave growth.

Air temps -- I didn't consider that.

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Alan.
My blog: It's not work, it's gardening!

Good question. In the context of my OH college notes, the prof. was referring to ambient air temps. I have a chart of air temps vs plant growth; in general it peaks about 86 degrees and falls off again. Photosynthesis is slowed down at low temperatures. At higher temperatures, plant respiration outstrips the available food produced from photosynthesis. Daily fluctiouations in air temperature are also important for plants to balance respiration and photosynthesis. There is a good borrowed OSU essay explaining this at:

http://www.ces.ncsu.edu/depts/hort/cons ... lants.html

I am not sure what the optimum temperature for growing bamboos are. It seems to vary with the species. In the case of bamboos, I think there are effects from both air and ground temps; warm air temps promote leaf growth. Warm soil temps promote rhizome and shooting growth. However, there are also effects of radiant heat of both, as well as the radiant heating effects of the sun. I belive that bamboos go semi-dormant in winter, and store food then. They also seem to rob their leaves of nitrogen just before shooting. That I when I feed my bamboos the most.

Another aspect in terms of greenhouse heating is something that I learned from some Russians a few years ago. Rather than heat the air in their greenouses, they heated the soil. It seems to be the right idea to me. I lived in a house with radiant heat flooring at the time. The idea is to heat the soil and keep that nice and warm. Convection causes the warm air above the soil to rise, and that in turn warms the plants. Also radiant heat from the ground hits the leaves in the form of infrared radiation and warms them. The rhizomes in bamboos would stay warm in the winter, and thus the plant would only be exposed to top kill at most but not rhizome kill. However, using this method, you would not want to heat the soil so that the plants shoot too early and then be exposed to a late spring frost. This area is notorious for early and late killing frosts.

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I am strongly agreeing with this idea, but I also have more to add to it. Bamboos that can make it through the winter with minimal to no leaf burn continue photosynthesis throughout fall and winter so by spring time, they have stored up enough energy to put out much larger shoots in a greater quantity resulting in an upsize.
Some less hardy bamboos that get fried by december or top killed will only put up survival growth with the stored energy in the rhizomes and even with surviving leaf buds will waste lots of energy leafing out not leaving much for new shoots.

My point is that keeping every leaf on the bamboo through winter is necessary for a bamboo to maximize it's increase in size year to year resulting in mature heights. This also varies for each bamboo because of the differences in energy storage since some can store enough energy to upsize even after a top kill, but the upsize would be greater making it through the winter.

I bought a greenhouse for my potted bamboos because I wanted to maximize the sunlight recieved by my plants throughout winter which would not be feasible under a grow-light indoors, or even using a south facing window. Plastic greenhouses can be set up around bamboo groves as well.

I also think getting a plastic greenhouse around bamboo groves in zones 3-5 may allow timber bamboos to exceed the listed heights in the zone given an adequate sustainable heat source applied in the greenhouse as well as the soil the grove is on. Only a 12 foot tall greenhouse would be needed for bamboos getting 20-25feet because I've also figured that they bend pretty easily without breaking.

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I just bought two 55gallon steel drums to hold water for my greenhouse over the winter costing me 16$ each. I'm not really sure if I should get a lid for them, but I don't really think its necessary because the barrels heat up quickly with sun and I don't think 15 hours of darkness and cold is enough to freeze this amount of water. It does take up about 12% if the greenhouse space with both barrels, but I could always stack the pots if I cant fit them all in the ground. I still have 64 square feet to work with.
The barrels are a little glossy so does anyone think its necessary to paint them flat black for even better results?

BARRELS

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I would not bother paining them. They will dull with time anyway. One thing to note is that steel drums can and will rupture if they freeze. Ice expands. I had an exposed one inch steel water line break on me a few winters ago here when they got to 10 degrees F. They looked like they exploded. And that was just one inch water line icing up. As GHM recommends below, use antifreeze. And use the non-toxic stuff for toilets and the like.

My bother uses the blue plastic food grade barrels that have really thick plastic, and they can take full freezing to ice and not break. They froze here in his greenhouse this winter several times in 18 degree overnight lows. I would expect NY to get a lot colder and for longer periods than here. The plastic ones are typically sold and used around here for catching rain water. I have gotten the metal ones (honey and glycerin barrels) with lids, as the lids are nice places to put things (shelves) and more important, they keep the damn skeeters from breeding.

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I would lid them, and you will need to put in some antifreeze... not for freezing, but for rust prevention.

I put some 2x4 boards acrross between two barrels, and stacked plants on top. Gave me a shelf.

Thats not even really cold, but i suppose that is possible given that the containers don't absorb heat well, lack of sunlight, prolonged below freezing temps and cold soil temps. I always thought that since sunlight usually raised ambient temperatures about 30F(so avg Jan high of 32F--->62F) it would be pretty hard to freeze over 100gals of water in a small greenhouse considering the duration of time required of below freezing temps.

Here are a few possible solutions to the heat problem. I could get 2 more 55 gallon barrels and just put plants on top, ensure long side is facing south and install reflective material on the north side to trap more heat, put the barrels on bricks, or hard foam so its heat doesn't go straight into the ground, stack snow on the 3 other sides of greenhouse for further insulation, create a wind-block barrier on the NW side of greenhouse where cold winds usually come from, ect.

I'm going to put my electronic thermometer in the greenhouse to record highs and lows and turning on an electric heater would be my last resort because I really want my greenhouse to rely solely on solar energy so that the green house is self sustainable even though its so much easier to install a heater. This is going to be a pretty fun project.


Does the rust create cracks in the barrel within a few months or does it take much longer? They only cost 16$ each about the same cost as antifreeze so I'm not sure if the drums are worth it since I easily go out and buy another one.

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Sunlight? In winter? In Hillsboro? Averages are very misleading. We had a lot of ice storms, lots of snow (more than the last 20 years or so) and temps stayed low here, from 18 at night to 25-28 in the day for weeks at a time. I think that the blue plastic barrels are 50 gallons. They froze solid in about 4 days.





They will rust up and crack pretty fast. I doubt that the antifreeze will work as a corrosion inhibitor. I used a special corrosion inhibitor in my outdoor wood boiler, but not antifreeze, as antifreeze somewhat reduces water's heat transfer ability, and the boiler stayed on all the time. You could use a cheap chunk of metal made of zink or magnesium to work as a sacraficial anode rod and protect the steel in the drums. Just have to bond it to the drums.

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