Question
In a previous Q by someone you said the Blue spruce had a tap root and then water feeder root that spread out.  I am putting a green house about 12 feet from 30 year old blue spruce. There is a large feeder root that is on top of the ground and going down right where I need to pour a concrete footing for the green house foundation.  It may be 10 to 12 inches in diameter where I have to cut it off.  Will this kill the tree, or will it send out more roots elsewhere?

Will the tree be more likely to blow over if I cut this root off?
Please let me know what you think will happen.
We live in Seattle and get lots of rain most of the year but, in the summer there is much less to sustain the tree.  My wife has lots of flowers and is watering every day all around the tree, but I don't know if that is helping the tree any.

Answer
No cutting one of the lateral roots will not kill the tree. In fact you can cut off up to about 25 % of the roots and not cause the tree to die. You might get some foliage dieback but the tree will survive.
These do have tap roots and this will more than compensate for the lateral roots being cut and will hold the tree during winds so there is not a problem with stability.
At the very most you could get some foliage damage on that side of the tree but I would expect you will see no damage.