pointer80
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Location: northern Michigan

question on seedling temps

hello all, As I mentioned in another post I bought a cheap greenhouse(picture enclosed) to put in my insulated shop that stays about 43 degrees or so when the outside temps dip down in the 20's or so. I am going to put a milk house heater in the green house for more heat and also use heat mats and fluorescent lights for my grow lights. My question is what is the best temp to maintain inside the green house? Also whats the minimum temp the seedlings can take? I am growing the usual garden veggies. Thanks all.
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MoonShadows
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Basically as long as you keep your plants from frost or freezing they will live. But they grow at a slowed pace when subjected to lower temperatures,even if just during nights. I would strive to keep them in at least the 50-60 range and if temps dip into the 40s you still have a safety net. You need to be real careful where you record your temps when you get in the lower 40s. Any eye level thermometer reading below 40F will mean a lower temperature at ground level.

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applestar
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Yep I agree. Get thermometer(s) with max/min and monitor the temperatures at floor levels to ceiling levels until you know what to expect — I use remote sensors at various indoor gardening areas and outside areas — and the base station stays inside. You can even get smartphone app linked ones now, though they are more pricey. Temperature will be higher while the lights are on and lower once they are turned off and cool down. Shelves above the lights will be warmer and can supply some bottom heat while they are on.

Take advantage of the micro-thermal layers and put cold/cool weather seedlings (onions, lettuce,etc.) on lower levels (45-60°F), tomatoes and cabbage/broccoli on middle levels (55-70°F) and warm weather seedlings (peppers and eggplants) on upper levels (65-80°F — increase to these levels with heat mats if necessary).


...be sure to guard against mice — they favor peppers and broccoli seedlings... tomato and cabbage, too, if they are hungry.

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rainbowgardener
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As long as the air is the 45 degrees you said your barn is, your plants will be fine. What matters then is the soil temperature. Above freezing, plants are more sensitive to soil temp than air temp. You manage the soil temp with the heat mats.

pointer80
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Thanks all, I should be able to maintain 70+ temps with no problem inside the greenhouse. I also plan on putting some foam sheathing down on the concrete to help insulate the concrete. Also the days are starting to warm up around here as we speak so that will help.

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MoonShadows
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Foam on the floor will definitely help keep the cold slab from lowering the temps.

pointer80
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Joined: Sun Mar 24, 2013 1:50 pm
Location: northern Michigan

MoonShadows wrote:Foam on the floor will definitely help keep the cold slab from lowering the temps.
That's my thoughts, I also have put it on my shelves in the past when I use my heat mats to help send more heat up.

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MoonShadows
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Good idea. I wouldn't have thought about that.



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