Question
Hi,
I have about 600 1.5 year old tree seedlings (Colardo Blue Spruce and some White Pine) in foot diameter, 2 feet deep pots.  I would like to move them indoors (kinda create an indoor tree farm) and put them under florescent lights.  I have a large home and would like to see what the possibility of growing them to 10 feet is possible.  Of course I will put them in larger pots later as they are only 1.5 feet tall seeing as they are just seedlings.  I will use them to plant on the property of my home in 5 years.  Is there any information avaliable on this matter.  I live in Toronto.  Your help is greatly appreciated.  Cheers!

Answer
I was poking around, looking for information on indoor growing equipment, then in dawned on me that  indoor 10-foot tall trees are HUGE!  And 600 of then could easily fill 20,000 square feet of space.  My Church has a Norfolk Island Pine (Araucaria Hetrophylla) in its entry.  It is not suited for outdoors in our area. It is about 15-17 feet tall, and it will NEVER go outside.  It also takes up a good 60 square feet of real estate.  And it is next to a 20-foot window.

Your Blue Spure (Picea) & White Pine (Pinus strobus) will reach upwards of 40 feet (12 meters), once they go outside.

Since you Live in Toronto, these seedlings should be out-door hardy in their pots by the time they reach about 8-10 inches tall (20-25 cm).  If they are not hardy at that size, then they are the wrong trees for your new home.  I have a 2-year old Cedar seedling on my back porch that I nursed through last winter, but it is going to stay outside this year...It is about 10 inches tall.  

Growing indoor trees are not the problem, energy & space are.  I have never heard of any commercial growing operation grow trees indoors or in greenhouses much past the seedling stage, as the energy bill required in electricity for grow lights would be enormous.  Even "pot farms" cannot get their illegal shrubs much bigger than 5 feet or so without the authorities wondering why their electric meter is smoking!   That is why greenhouses are so much better - especially in challenging areas like Toronto.  The sunshine does all the work.

To your question, to get these seedlings to the size that their survival rate is acceptable, you can use grow lamps or a sunny window for the first year or two.  Much beyond the 8-10 inch height, and they should go outside for the Winter.  

~M

(ps: My apologies for not converting all the sizes I refer to into metric!  Hopefully, you get the idea)