While its needles are technically silver blue, the Colorado blue spruce (Picea pungens) also goes by the name of green spruce. This tree grows in hardiness zones 2 to 8 and can be planted throughout northern California. Green spruce trees require low to moderate care; these trees aren't finicky and can withstand low water in this drought-prone state. Native to North America, the green spruce is a popular evergreen among homeowners and makes a pretty Christmas tree.
Plant your green spruce in an area where the tree has enough room to mature. These trees average 50 feet tall and 20 feet wide. Dig a hole twice as wide and equally deep as the tree's root ball, then remove your green spruce from its container. Loosen its root ball by rolling it between your fingers, then place the tree in the ground so it sits in the same depth in the soil as it did in its container. Cover the hole with soil to plant the tree.
Water your green spruce regularly. Give the tree 1 inch of water per week unless it receives that much water in rainfall during the winter months, California's rainy season. While green spruce are moderately drought tolerant, watering helps keep the tree healthy and prevents disease.
Prune the green spruce each year in late winter to shape the tree and remove unhealthy wood. Trim off dead, broken or diseased branches (which will have brown needles). Cut long branches back to side buds to control the size of individual limbs. Avoid shearing your spruce with hedge clippers; instead, use hand pruners and work one limb at a time. Keep the natural sloping shape of the tree.
Watch for signs of insect pest and plant disease. Green spruce can develop galls or blackish round growths; these can be pruned off to control the disease. Spruce trees can also develop several diseases that cause needles to turn yellow, brown or rust-colored. If you observe discoloration, contact your county extension officer to obtain a diagnosis and treatment advice.
Fertilize green spruce each year in the spring using 10-10-10 fertilizer. Scatter the dry fertilizer on the soil around the base of the tree then water the soil to disperse the nutrients. Use the manufacturer's recommended dose range based on the size of your spruce tree's diameter.