Minnesota's growing season, lasting from May to September, requires plants to complete their annual growth spurts relatively quickly. A key difference between the Black Hills spruce (Picea glauca Densata) and the Austrian pine (Pinus nigra) is the growth rate. The spruce is much slower-growing than the pine, but you still should allow ample space between the trees to allow them to mature without encroaching upon each other. Provide them both a fertile, well-draining soil in full sun for best development of their attractive, pyramid-like forms.
Assess your landscape's size. It must be large (wide) enough to accommodate both trees when mature. A Black Hills spruce matures to 20 to 40 feet tall and 10 to 15 feet wide, while Austrian pines grow 50 to 60 feet tall and 20 to 40 feet wide. You ideally need an area at least 40 feet wide.
Position both trees in their potted nursery containers in the area you wish to plant them. Space them visually where you like them to be planted.
Measure outward with a tape measure from each tree to determine their future extent of branches. For example, the Black Hills spruce grows 10 to 15 feet wide overall, according to the Missouri Botanical Garden. That means from its trunk the branches will radiate outward in all directions 5 to 8 feet. The Austrian pine grows 20 to 40 feet wide overall, with branches that radiate outward 10 to 20 feet, according to Michael Dirr in "Dirr's Hardy Trees and Shrubs."
Relocate the containerized trees on the ground until their expected (future) widths do not overlap more than 3 feet. This means the spacing between the spruce and the pine should range between a minimum of 20 to 30 feet. Within this range, you can position the trees to your aesthetic or other needs before finally planting them.