I planted 3 blue spruce and they grew rapidly — too big for where I put them ,so I want to transplant and am scared to. When ,and how much root ball needs to come out ? Thanks you .
Now (the winter) is a great time. The tree will be dormant and will have the best chance of survival. How big the root ball is depends on how big the tree is however the bigger the better. The less root system you disturb the better. The more roots you rip out and leave behind the more that have to re-grow and remember the root system in place has grown to support the size of the tree as it is now. So if you remove half of the root system you will have half as much root system available to sustain the canopy of the tree. So you will have to cut the tree back and then water, water & water so the roots that are left can absorb as much water as possible to support the canopy. Also using a transplanting fertilizer would help your cause 10-52-10 would be good or something akin to that with a big middle number (phosphorus).