Blue spruce (Picea pungens) is a pyramidal evergreen tree known for its attractive blue needles. Native to the Western United States, blue spruce performs best in USDA Plant Hardiness zones 2 through 7, where they are often used as privacy screens, windbreaks or landscape specimens. Though blue spruce are low-maintenance trees, there are a few things you can do to make sure your tree's foliage stays as blue and beautiful as possible.
Select a blue spruce cultivar know for its intensely blue foliage. These include Picea pungens "Bakeri," "Hoopsi," "Moerheim" and "Fat Albert."
Plant your blue spruce in a full sun location with moist, fertile, well-draining soil. Select a site that receives direct sunlight for a minimum of six hours a day to ensure the tree retains its attractive blue colouring. Plant the tree at the same depth it was growing in its nursery pot.
Irrigate the blue spruce regularly to maintain moist soil; frequent irrigation helps keep the foliage healthy and blue. Drought-stressed trees may suffer from unsightly faded or browned foliage. For best results, provide the tree with 1 inch of supplemental irrigation per week during the spring and summer.
Fertilise the blue spruce three times a year to provide nutrients for healthy growth and development. Feed the tree with a granular 12-12-12 fertiliser in April; apply subsequent applications at the beginning of June and August. Use the fertiliser according to instructions on the product label.
Prune any discoloured, diseased or dead foliage from your blue spruce tree, as needed, to keep it healthy and attractive. Use sharpened and sterilised pruning shears or loppers.
Spread a 4-inch layer of organic mulch on the surface of the soil around your blue spruce tree. Mulch helps the soil conserve moisture and prevents the growth of weeds.
Pests such as Eastern Spruce galls, Spruce needle miners, aphids and spider mites damage blue spruce trees and may cause them to drop their blue needles. Treat heavily infested trees with an insecticide or miticide if their health begins to suffer.