and what have you got going?
To help get the ball rolling, here are excerpts from a conversation on the MG list:
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How does ambient temperature affect the growth of plants started from seed?
Assuming that light, moisture, fertilizer, and soil/starting mix are otherwise adequate, how much is growth of seedlings affected by air temperature? Should I start my tomatoes and other plants earlier than is recommended on the seed packages and university literature (one week, two weeks, three, ???) if I grow them in a cool 65 degree basement rather than at 75 or 85 degrees?
I use a seed heating mat/germination mat to keep the soil mix warm while the seeds are actually germinating, but do not have enough warming mats for the entire propagating period for all the seedlings I try to start. I used a small electric space heater last season to add extra heat to an enclosed area of the basement, but the utility bill ended up competing with the national debt.
Will plants grown at lower temperatures be set back once they are set out in the garden? Will my tomatoes wake up and begin ripening in mid-October?
I guess what I am looking for is personal experiences and ideas.
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I suspect the ambient temps slow the growth of seedlings a bit. After all, greenhouse growers drop the temps to keep plants "on hold". In fact, John Erwin, a floriculture prof, has done a lot of research on using cooler temps in lieu of growth regulators in bedding crops. He calls it "DIF" so you might check that out. He suggested dropping greenhouse temps a certain amount, at night, IIRC.
Having said that, like you I've started more seedlings in my chilly basement than I've grow mats for. I started the seeds on the mat then when they were up, maybe had their first set of true leaves, I moved them onto a shop table under lights. My basement isn't a toasty 65. It's usually 55 or so. (I have a space heater in my basement office to keep my fingers and other relevant parts from freezing.)
When I've taken a spring trip, I've prevailed upon a colleague to keep an eye on my babies and moved them into the Hort. greenhouse while I was gone. (I limited myself to one plug tray.) They have grown significantly larger by the time I returned. So, yes, more light and 70 degree F temps help bunches when speeding seedlings to maturity.
How much you should extend lead time??? Hmmm. That depends on how big you want your transplants by planting out date. I've tended to start seedling a bit earlier than recommended, by maybe a couple of weeks. (Yeah, there was the quarter I was taking a bonehead Algebra refresher and was so crazed I started seeds in Feb., including tomatoes. I transplanted those puppies a couple of times, the last into "beer cups" when they were close to a foot tall. Blame it on Algebra. It never happened again. ;-)
I don't think the plants are set back if grown cool. I wonder if they'd be set back more if grown warm, then cooled down. (????) In spring you can have cool evenings. I've harvested tomatoes pretty much the same time everyone else has.
I suspect cool seed starting medium is a greater limiting factor. Way back when I was still doing accounting for a living, I started some alpine strawberries from seed. The first batch were planted and left at ambient basement temps. They took *forever* to come up. I started a second batch and left the tray in the kitchen, which was much warmer. They were up in days.
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I wouldn't call 65 degrees a "lower temperature". Your tomato seedlings will do just fine at that temp. You say that all the other factors are adequate, but your tomato seedlings would disagree with you. Artificial light is just not the same as good old sunlight, artificially fertilized soil mix is not the same as good organic garden soil and moisture in the medium is not as even as it is out in the garden, either. And, air humidity and movement outside is better for your tomatoes than the stagnant dry air indoors, too. The more air is heated by your furnace, the drier it gets, so 85 degrees indoors is not like 85 degrees outside during our humid Minnesota summers!
No, I wouldn't start tomatoes earlier than recommended. They'll suffer more from having to be inside, under less than adequate conditions, for a longer period of time.
Regardless of what temperature they were accustomed to in your house, it will take them awhile to get established in the garden. Be very careful to harden them off properly before putting them in the ground.
When tomatoes begin bearing has more to do with weather conditions through the summer (which, of course, you have no control over) than how early you start them indoors, although the variety you choose makes a difference, as well.
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My basement growing situation sounds similar to yours. Keeping the lights 2-3" above the plants produces nice dark green plants that take right off when planted outside. I usually start them during the first couple of weeks of April. I have started some later and they seem to catch up pretty fast once transplanted to the garden.
So if you are just growing transplants, I would say don't worry about trying to supply the extra heat. If you are wanting larger plants then you should start them earlier.
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I think it is most important to have it warmer in the room, around 75F or so, to get the seeds to germinate. Then, once the germinate, a little cooler is best so the seedlings don't get real tall and leggy. Ideal around 65F. Start your tomatoes and peppers about 8 weeks prior to the usual last frost in your area. Since tomatoes and peppers like heat, plan on putting them in the garden around June 1st. So you really don't have to start your seeds until the end of March or Beginning of April. Also doesn't hurt to have a fan in the room on low to simulate a light breeze to help the seedlings be a little stronger. I don't have any heat mats, just a space heater in my furnace room to have the warm temps initially and I have a pretty good germination rate. Growing the seedlings at a lower temp will not hurt the plants after they are set out. Just make sure you have a hardening-off period to get the plants used to the sunlight and the wind and you should do just fine.
jel48
zenpotter
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