How long for a lime tree to produce fruit ?

They will start producing even at the size you have. But it is best to enjoy the scent of the flowers and remove any fruit until the branches are strong enough to hold them. Usually about 3 years. They have both a tap root and lateral roots. They don't spread out much further than the drip line of the tree. It is best planted a little higher than the surrounding soil.

Here is a good site to read about planting your tree.

http://www.brighterblooms.com/planting-directions/...

Mine is a Key Lime which I bought last fall at Lowe's. I had no hope of getting fruit this year but about a month ago the flowers started setting fruit. Now I have about 70 limes the size of a nickle. The plant is about 4 ft tall and is in a 15 gallon bucket.

I planted 3' satsuma in March. There were flowers and small fruit on the tree. I removed the fruit to avoid having the plant put its energy into fruit production instead of developing a good root system. I did not amend the soil nor did I add any fertilizer. Early next spring I will fertilize and should have fruit next fall.

Dont expect fruit for at least 3-5 years after you plant the tree. All citrus have roots that grow outward, although they will some times have one that grows downward.