Greenhouse and Growing from Seed Question ??

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This will be my first year using my greenhouse my husband put up for me last fall. About a 10X12 plastic kit greenhouse. Really came out well and am pleased with it. Here is my question...I always started my seeds in the house under lights in the past. Planted my little seeds this past week and the greenhouse gets into the 100's during the day and drops to around 40 degress at night. Last night I put the kerosene heater in there and at midnight the temp was 69 degrees. Don't know if I like doing that because this morning the greenhouse smells awfull with the smell of kerosene. Will the seeds germinate well without constant heat and once they come up will they need additional light even in the greenhouse. Any help would be appreciated !!! Have a short growing season here in upstate PA and don't have too much time to experiment. Thanks !!!!

-- Helena (windyacs@npacc.net), April 13, 2002

Answers

We live in North Carolina. Although our temperatures are more moderate than in upstate PA, I started seeds in February, which is probably the temperature range you're experiencing now.

For the most part, I've been germinating indoors then moving flats to the greenhouse when the seedlings start to appear to avoid the possible problems of too cold nights for germination. (Before the seedlings appear, you don't need light . . . just warmth and moisture.) A few weeks ago I got braver, and decided to start some directly in the greenhouse. No problem, even with evenings in the low 30's.

After the move to our unheated greenhouse, we protect against cold nights by covering the seedlings with a light row cover. When the temperature dropped to 22 degrees, we used heavier blankets and only lost a few. The seedlings couldn't tolerate the weight of a blanket, so we put them in boxes with the sides of the boxes extending well above the top of the seedlings. The boxes then took the weight of the blankets--not the seedlings.

We're still experimenting with additional lighting in the greenhouse. Most of our stuff has done quite well without it. Personally, I think it's more important in the winter if you're trying to grow things with much shorter days. We do have electricity in the greenhouse so that we can use lights/fans.

By far the biggest problem we've been experiencing is the heat during the day. We installed attic fans in the wall near the door. They are thermostatically controlled to turn on when internal temperatures reach 80 degrees. We have windows (which we open during the day) . . . the attic fans help draw the hot air out and the cooler air in. It's warmer in the greenhouse than outside during the day. Once the fans kick on though, we're usually within 10 degrees or so of the outside temperature.

Frankly, our greenhouse is too big to efficiently heat, so I've started calling it a big walk-in cold frame.

We're primarily using it for starting seeds in the spring, extending harvest in the fall and growing cold-hardy vegetables in the fall/winter/spring. This winter we enjoyed lettuce and swiss chard. Towards the end of the summer, I'm going to try to plant some potatoes, cabbage, lettuce, spinach, and peas and see how they do over the winter. (Hey--it really is a big walk-in cold frame.)

-- Julie Woessner (jwoessner@rtmx.net), April 13, 2002.


Hi Helena, I'm at the same stage you are! New greenhouse, wondering how to use it. I started seeds under lights, with bottom heat (in the house). Let the plants get good & sturdy before moving out to the greenhouse. Once in the greenhouse, they get no additional heat or light. I think the seedlings would get straggly without that initial heavy dose of light and heat indoors.

-- Shannon at Grateful Acres Animal Sanctuary (gratacres@aol.com), April 13, 2002.

Wow, a greenhouse! What fun! Have you thought of putting some thermal mass inside your greenhouse? A couple of 55 gal drums painted black, dark blue, dark green or dark red would absorb heat during the day and give it back at night, moderating your temps. you can use them to set pots on so the space isn't lost. Or you can put milk jugs filled with water that has a little dye in them under the benches, just make sure the sun hits them.

-- kim in CO (kimk61252@hotmail.com), April 13, 2002.

How about using a simple passive solar heater...paint 55 gal drums flat black...fill with water, the sun will warm them up during the day, and they will radiate the warmth to the beds stacked upon them at night.

-- BT Clowne (lakebreezefan@yahoo.com), April 13, 2002.

We've tried that plastic drum painted black routine, didn't work, though some people have had luck with it.

We also have a greenhouse, 17 x 9, keep it heated with a small kerosene heater in winter. We had also lined it with that bubblewrap insulation that has aluminum foil on both sides, that really helped, and clear plastic at the top. I started my seeds indoors, rigged up the grow lights right over top, otherwise the seedlings get spindly if they don't get enough light. Once they were up and growing, then they were put into the greenhouse. We're fortunate to have 3 of those automatic vents that came with the greenhouse, and we have a small fan on a shelf up near the ceiling that is on constantly to keep the air circulating. Before we got that we had mildew on some pots of geraniums that were jammed together at the back.

-Chelsea

-- Chelsea (rmbehr@istar.ca), April 13, 2002.



I am also fiddling with my new greenhouse. On warm days I leave a door open to vent it, I have also left open a window on the opposite side that I put in for just that purpose. My little heater didn't put out enough heat to warm the entire greenhouse so I put the seedlings in the warm spot in FRONT of the space heater, but that dried out the seedlings too quickly. Next year I will try one of those covered seed trays to keep the humidity up and decrease the rate at which they dried out. I have several seedlings growing directly in the ground of the greenhouse that are ready to transplant out: they are doing better for me than the seedlings in pots.

-- Terri (hooperterri@prodigy.net), April 13, 2002.

If the green house hits 100 plus during the day, ventilate it. If you want robust and stout seedlings, keep the daytime temp closer to 60-70 degrees...the 40 degree nights are not a problem...but i would try to avoid much cooler nights for good germination and growth...depending upn the species. Some perennial seedlings need cold nights and many seedlings are much more robust when they go out in the world if they had cool night temps in the house.

Many good books on this topic...look up greenhouse management and greenhouse production...

If you are growing tomatoes then I say let the day time highs hit 75 and the nighttime lows hit 70...you will sell every one you ripen and more than pay for theyears worth of propane...zone 4 experience talking here.

Oscar

-- Oscar Will (owill@mail.whittier.edu), April 13, 2002.


Where do you get the plans for a greenhouse? What features did you like and dislike? What would you do different?

-- Hank (hsnrs@att.net), April 16, 2002.

We,too, have a new greenhouse. I started more of seeds in it. I started in late February. When we contructed the greenhouse in the winter we did not install any of the vents in order to have a warmer spring green house. (Don't worry they are in now!) This avoided the cold draft possibility.

We put in two 55 gallon drums(painted black)on the north side of the greenhouse.

In order to keep the seeds and seedlings warm at night I would cover them with a white garden cover clothes and put my husbands halogen work light UNDER the bench. Our benches are wood framed with wire cloth "tops". This allowed the heat to rise up and get "caught" by the cloth. While all my seeds did not germinate ( and that is from something else) I did not loose one plant to frost/cold.

I also put a cold frame inside the green house to germinate and protect the most tender plants. The coldframe never got below 50 so I will make more for use in the fall and next year. I am also going to try to grow vegetables thoughout the winter in there. I make a 15 inch high cold frame. I put a piece of stryfoam insulation on the bottom and plant in containers. Obviously I cover with an old storm window.

Now, if I could just keep it really cool in there now! Even when a shade cloth cover, with the fans running it is close to 100 in there today. Of course, it is 95 outside.

-- Chris in PA (CLMngs@aol.com), April 17, 2002.


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