Blue Spruce is frequently used as a landscaping tree due to its classic pyramidal form and the blue-green colour of its needles. It does not tolerate varying water conditions, however, such as too much moisture or a period of drought. The needles of Blue Spruce often turn brown over long dry winters or excessively wet winters.
One of the most common reasons blue spruce trees turn brown over winter is lack of moisture. Blue Spruce trees require year-round moisture, and a dry winter may cause the Blue Spruce to become stressed and turn brown. Too much water may damage the tree, as well, smothering and killing the tree's roots and causing its needles to turn brown; a particularly wet winter may also have this effect on the Blue Spruce.
Inadequate water during the winter causes trees to become stressed and makes them more susceptible to disease, so one of the first things you want to do if the needles of your Blue Spruce have turned brown over the winter is to examine the tree for signs of disease. Some diseases themselves may cause the needles to turn brown, such as cytospora canker and rhizosphaera needle cast, both caused by fungi. Other signs of disease include white sap leakage, small black spots on the needles and branch dieback. Consult your local county extension for help with a diagnosis if you find evidence of disease in the tree.
In addition to disease, Blue Spruce trees stressed by drought or too much water over the winter are vulnerable to attack by pests, particularly bark beetles. The beetles bore into the bark of a stressed tree in the spring and set up breeding galleries in its living tissue. Signs that bark beetles are present include holes in the bark and the presence of woodpeckers, which feed on the beetles. Non-stressed trees are naturally able to defend against an attack. Once the beetles are present, they are difficult to manage and may even kill a tree. Consult your local county extension office for control recommendations.
While you can't make up for lack of water or too much water after the fact, you can take steps to improve a Blue Spruce tree's vigour to ensure it does not suffer further needle damage the following winter. If the tree has not received adequate water, make sure it receives water not only throughout the summer, but through the following winter, as well. Water about once a week during the summer. Stop watering the tree approximately a month before the first killing frost is due in your area, then water again deeply after a couple of killing frosts have passed. Aerate the soil around the tree to allow for water penetration and proper drainage. Mulching around the tree will help the soil retain moisture. Fertilise the tree in the spring with a balanced fertiliser to maintain vigour.