Scotch pine, or Scots pine ("Pinus sylvestris"), and blue spruce ("Picea glauca") are attractive trees often used for Christmas trees and ornamentals. Both are long-lived conifers with blue-green needles and both reach average heights of 100 feet. Despite theses similarities, they look very different and are not difficult to tell apart.
Blue spruce is native to mountainous areas in the west, specifically Idaho, Wyoming, Colorado, Utah, Arizona and New Mexico. Blue spruce also occurs in the wild of some Northeastern areas where it has escaped from cultivation. Scotch pine, on the other hand, is found in the Northeastern United States and in some areas of the Midwest. Blue spruce is slightly more hardy, able to handle USDA hardiness zone 2, while Scotch pine is hardy to zone 3.
Stem and Branches
Scotch pine starts with a pyramidal shape as a young tree, which becomes more rounded or flat-topped as the tree ages. Scotch pine stems are also often crooked when the tree is young. Blue spruce trees maintain a pyramidal shape as they age. Scotch pine bark is thick and has crevices at the bottom of the tree. On the upper part of the tree, the bark is thinner, smooth and often flaky or peeling. Bark colour is orange-brown at the top of the tree and gets darker toward the bottom. Blue spruce bark is thick, grey-brown, furrowed and slightly scaly.
Both trees have blue-green needles, but blue spruce needles can also have a silvery appearance. Blue spruce needles grow individually from the twig, while Scotch pine needles grow in pairs. Scotch pine needles are also twisted with a rough surface, while blue spruce needles are straight with four sides and sharp points. Scotch pine needles are longer at 1.5 to 3 inches, compared to 0.75 to 1.25 inches for blue spruce.
The seed-bearing cones of blue spruce are larger, at 2.5 to 4 inches, than those of Scotch pine, which are 1.5 to 2.5 inches. Blue spruce cones are tan or light yellow-brown coloured with papery, elliptical scales with narrow tips. Scotch pine cones are grey-brown with diamond-shaped scales. The seeds of Scotch pine are brownish-grey, while blue spruce seeds are chestnut brown.