By John Chapin
Over the past few years, many homeowners have been alarmed by what seems to be a sudden decline of their blue spruce trees. Throughout the Midwest, Colorado blue spruces have been showing needle loss, dead branches, and browning foliage. The first sign of trouble is the browning of needles on the lower branches, which gradually spreads upwards. Eventually, the whole tree drops its needles and dies. This is due to a combination of factors, and unfortunately, there is little that can be done to save them.
Some experts say the reason for their decline is due to the fact Colorado blue spruces are not native to the Midwest, but these trees have been successfully grown in this area since the nineteenth century, as evidenced by beautiful mature specimens in yards and public areas. Their demise is more likely due to a combination of several environmental conditions as well as poor sitting when planting.
Over the past decade, the Midwest has experienced not only a serious drought but also continuing mini-droughts, four to six weeks of very low rainfall occurring at different times of the growing season. Fortunately, each dry period has been either preceded or followed by near-record rainfall. In 2016, we had five weeks of almost no rain in late spring, extending through almost the entire month of June, followed by one of the wettest Julys on record. While none of these dry spells qualify as a drought, they do put stress on plants. Extreme temperature fluctuations, hot summers, warm winters, and late frosts add to the stress.
Colorado blue spruces perform best on moist, well-drained loam to sandy soils with a pH of 6.0-7.5 and full sunlight. Unfortunately, most soils in Central Indiana are alkaline, heavy soils, with poor drainage. Under ideal conditions, in full sunlight, spruces will grow well, but when environmental factors are unfavorable, they decline rapidly. Poor drainage will kill newly planted trees in a year or less. If the tree is planted where the ground stays saturated after a heavy rain, it’s under a death sentence.
However, even with proper siting, the environmental conditions over the past decade are now causing problems for blue spruces from a combination of several diseases and insect infestations. Diseases include Cytospora canker, Rhizosphaera, and Stigmina. Insect pests include bagworms and mites. Any of the diseases can be fatal, and insect infestations weaken trees to make them more susceptible to the diseases. Treatment of the diseases is expensive and not always successful.
If one is fortunate enough to have a blue spruce, properly sited and not showing signs of decline, the best procedure is prevention. Adding 3” of mulch around the tree, extending to the outermost tips of the branches increases overall health in many ways. Water deeply if dry conditions occur, and fertilize each spring. With proper siting and care, you should be able to enjoy your blue spruce for many years to come.