Seedling growth rate: Inside VS outside


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Fresno, CA. Were all the food comes from if we ha
I planted out hundreds, if not thousands of seedlings this year. For fun I grabbed one (Acer Campestre), put it in my standard course mix soil and put it in a south facing window. This was kind of an experiment for my daughter who I helped plant some morning glory seeds in the same window. I didn't even expect the seedling to do well at all.

To my surprise it has put on two sets of true leave and is now pushing a third set of leaves! The ones outside still only have the first set of true leaves.

What is going on here? Is it just because the seedling is getting 65-70 degrees 24 hours a day? How long can they grow like this? I have a feeling that when summer comes it will be way too hot in the window. I have hear over and over again that maples need to be outside. Is a seedling the exception?

Please tell me what you guys think.

Here are two pictures to show the amazing difference in growth rate.


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In my youth i had an apple seedling in my window,it did well but then dried out and was no more.

I did not know about hardening off seedlings at that tender age,and i wanted it to grow in the window as outside was an alien place full of things i didn't know.
Lack of adequate light will cause an elongation as the plant tries to find enough light. This is not "growth" in the usual sense. Over time, the outoor seedlings will grow more and be stronger.
"I have a feeling that when summer comes it will be way too hot in the window. I have hear over and over again that maples need to be outside. Is a seedling the exception?"

Hardly. Seedlings grow. That's what they do in the spring. They're programmed for fast vigorous growth once the soil is warm enough--above 55 F for many temperate species. Given constant 70 F warmth at the root zone inside, the plant has a green light to explode with growth. They will grow like crazy--even inside--for a time. Sustained growth, over a period of months, inside, however, will be long lanky and mostly worthless for bonsai not to mention that the plant will probably burn itself out by summer.

Come summer, your AC will contribute to dried out foliage and spider mite infestations.

Come fall, your seedling (if it's still limping along) won't be able to prepare itself for outside winter storage, as it won't experience frosts and freezes that stimulate dormancy.

Come winter, the seedling might still have leaves--which means it's using up energy--which won't be available to it come spring.
Your experiment is not controlled.

Try bottom heat (reptile matt, gro matt, etc etc) on the seedlings outside and get back to me.....
I don't plan on making anything out of this or even keeping this inside forever. As i said it was for my 2 year old daughter. I was just surprised by the rapid growth and it got the wheels turning. I planted out a few hundred or so Amur maples last year and a year later the tallest one stands about 3" tall. If heat is all that is needed for this kind of growth I might start thinking along the lines of heating mat etc.
Mr. Grizzly, just a thought but Amur are something we use in the colder regions of the states due to problems with cold hardiness regarding tridents and palmatum. Living in an area with mild winter temps like you are I would surely be focusing on less finicky, tried and true species. I do have to admit to curiosity regarding Amur maples professed tendency to drop branches and whether the same holds true in a warmer climate such as yours.

Update. I moved a trident inside to see how it would do and once again it is growing a lot faster than it's brothers.

I realize as some have said this isn't best for bonsai if it causes long growth. Also that if I were to heat the seedlings outside they might grow faster, but I don't have the ability/money to do that.

It's just a cool experiment. Here are a few pics to compare the size of those in the seedbad vs those inside.

The red pot is the acer campestre, the other is the trident. The trident is harder to tell, but still about 2 times larger than it's brothers. The campestre also got about a month head start on the trident being inside.


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grizzlywon, I agree with smoke. To make this a true experiment, you'd really need to control more of the variables involved. Your trees you've had indoors are individually planted in pots, where the trees you're keeping outside are not. Those left outside could already be competing a little for underground resources and crowding each other a little. Or it could be something else about the different containers, watering, etc. If you want this to be more scientific, I suggest you try it again next year with the same type of container, while tracking watering, temperature, etc. Yeah, it's a bit of a pain, but science can be that way.

If you wanted to try heating a tray of seeds some time, you could try what I've been trying this year. I have a terrarium heater (~$30) on a kitchen cooling rack raised about 3" off the surface of a table with some cardboard between it and the bottom of a seed starter tray to lower the seed temperature a little. I screwed up a little on my first try and I think I cooked some of the seeds toward the center, but they're Chinese elm and I have way more than I need so it isn't really a problem. I'm aiming for about 95 degrees, but I think I hit over 105 in the middle on a couple days. Those seeds that did start started very quickly.

These experiments you're trying are interesting though. But truthfully, I just wish I had some of those seedlings or your level of access to mature trident maples for seeds. :p
I know about the scientific process and still think this proves a lot. The seeds outside still have all the room they need and then some (the seed bed is about 5" of pure lava. I have dug quite a few of them up to transplant already and they have very little roots. Not only that, but there is no difference in rate of growth of one seedling that is by itself in a spot with no competition for space vs a seedling that is a crowded place.

As far as I'm concerned 64-67 degrees in my house has made these grow like crazy.

With that said, I'm not going to bring all my seedlings inside next year. I might bring in a few, but find some ways to get more heat to the ones outside like maybe using some plastic to make a greenhouse.
With that said, I'm not going to bring all my seedlings inside next year. I might bring in a few, but find some ways to get more heat to the ones outside like maybe using some plastic to make a greenhouse.

Leaving them directly next to the south side of your house will help a lot in warming them up.
I agree, the problem is that in the summer they would probably die from the 110 heat. I have them on the west side of my house. Pretty much in the only place I have room for them in my yard. It's a real postage stamp. Oh well, at least I have another year before we get the water meters turned on! Ouch!
Grizzly, you can put me in the group saying this is not a controlled experiment, and the results of your experiment are far from conclusive. A rapid growth rate does not necessarily equate with a healthy growth rate. On one hand, you could be giving them a serious head start as compared to the outdoor ones. On the other hand, the indoor seedlings may be pushing early, perhaps unhealthy growth in the less then ideal indoor environment, and may actually be set back over the rest of the year.

I think I have a way to give the results of your experiment some teeth, but you'll have to sacrifice some trees in the name of science. At the end of this growing season, pick 10 seedlings from each group, bare root them and dry them out, then weigh them. I propose that the group with the most dry mass grew most vigorously during the entire season. So, what do you think?

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Dave, good idea, I just don't have 10 in the house. I also will be turning the air conditioning on in about a month. So, I'll have to move these guys outside. The real test for me will be what they all look like at the end of the growing season. I have a suspicion that this one will be about double in size or even more.
Dave, one more thing. The Campestre looks very healthy. The leaves are unbelievable and beautiful green. (what is healthy growth?)
My question is, when will it head down hill inside? My guess is that it will when the air conditioning starts coming on.

But this is also species that is not recommended in my zone, yet it seems to thrive. I have a friend who has one and it grows like a weed. Another interesting thing is that he swears you can get root cuttings off this species. I don't know of any maples that have that quality.

He gave me one too and it is in its second year in a grow box and growing like crazy.
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