Is it Possible to Over-Fertilize a Norway Spruce Tree?

Identification

• Hailing from north and central Europe, the Norway spruce is winter hardy in U.S. Department of Agriculture plant hardiness zones 2 through 7. As a conifer, it produces 4- to 7-inch-long red-brown cones. Its needles are stiff, up to 3/4 inch long and a dark green color, although new growth emerges a lighter green. Pyramidal in shape, Norway spruce grows to a maximum height of 40 to 60 feet.

Over Fertilization

• All plants require vital nutrients, the most important of these being nitrogen, potassium and phosphorous. However, these can also run the risk of harming the plant, especially nitrogen. Although a common element in fertilizers, nitrogen can burn plant roots and stems if applied too often or in amounts too great. It also stimulates new growth, so when applied late in the growing season can cause trees to put on a growth spurt that will lower their winter hardiness. Lastly, it makes plants more lush and attractive to deer.

Proper Fertilization

• Proper fertilization depends on many factors. First, check whether the tree is nitrogen deficient. Common symptoms include stunted, yellowed foliage. Then conduct a soil test to see which other nutrients your soil may be missing. Which type of fertilizer you use and how much you apply will be determined by your soil’s deficiency and the tree’s needs, although Norway spruce generally does well with 1 to 4 ounces of 23-3-7-4 or 14-3-18-4 applied yearly. The best time to fertilize is in winter, when the tree is fully dormant and will not put out new growth in response.

Precautions

• Trees that have just been planted do not need fertilizer applications during their first growing season. Usually, they have plenty of nutrients left over from the nursery, and adding more risks damaging them. When trying to determine whether a tree is showing signs of stunting, keep in mind that while young trees often produce 8 to 12 inches of new growth per year, older trees may not. If the foliage still looks green and healthy, the tree may not need fertilization even when its growth slows.