Planting a blue spruce near house walls is usually a poor choice, and the tree pays for it within a decade. The problem is not the foundation. A blue spruce grows 10 to 20 feet wide, and a wall steals the room and airflow it needs to stay healthy. Good blue spruce spacing is the one thing most people skip, so the tree ends up jammed against siding it will eventually swallow.
"Now that one is a beauty," a neighbor said. He leaned over the fence to point at the young Fat Albert I had tucked beside the wall of my southern Wisconsin yard. It was waist high then, blue and tidy and easy to love. Eight years later that same tree pressed its lower branches flat against the gutters. It brushed the eaves every time the wind blew. The two spruces I planted out in the open got 12 to 24 feet of room each. They stood full and healthy, clean blue needles top to bottom, while the one by the wall thinned and browned from the ground up.
A wall traps moisture, and a blue spruce hates trapped moisture more than almost anything. Branches that touch your siding stay damp after rain. They never dry out in still air. That humid, stale pocket is just what Rhizosphaera needle cast and Cytospora canker need. Needle cast strips the inner and lower branches bare, and canker kills whole limbs from the trunk out. Once those two get going near a wall, you fight them for the life of the tree. A spruce planted in open air dries fast after a storm and shrugs both diseases off.
The numbers back up giving it space. Nurseries and extension offices put the planting distance at 12 to 24 feet (3.7 to 7.3 meters) between trees. The same logic applies to your wall. You might worry about roots cracking the foundation, but that fear is misplaced. Blue spruce roots stay shallow. About 73.6% sit in the top 2 feet (0.6 meters) of soil. The USDA still rates the tree as windfirm, so the roots are not your threat. The real issue is canopy width and airflow, not your concrete.
Keep a full-size blue spruce at least 15 to 20 feet (4.5 to 6 meters) from your house. Closer than that and the canopy crowds the wall, traps humidity, and invites needle cast and canker.
So plant the tree where it can breathe. Set a full-size blue spruce at least 15 to 20 feet (4.5 to 6 meters) from any wall. Measure from the trunk, not from where the branch tips sit today. That gap looks silly when your tree is knee high, but it matches the blue spruce mature width you will see in twenty years. Give it the room and the tree fills the space, keeps its lower branches, and never fights your building for air.
Before you dig, walk the spot with a tape measure and check what sits above and beside it. Look for the roof overhang, the gutters, your power line, and any window you want to keep clear. If you cannot find a clean 15 to 20 foot gap, the spot is wrong for a full-size spruce, and no amount of pruning later will fix that. It is far easier to pick a better location now than to take a saw to a mature tree in ten years.
If you truly want a spruce hugging your foundation, pick a dwarf instead of fighting a giant. A cultivar like Glauca Globosa stays compact at 3 to 5 feet and holds the same silvery blue color you wanted in the first place. You can set it in a foundation bed, near a path, or under a window, and it never reaches your eaves. Match the tree to your spot and you skip the saw, the disease, and the regret a decade down the road.
Read the full article: Blue Spruce: Complete Care and Growing Guide
